Songbird Ecology in Southwestern 

Forest Service 

Ponderosa Pine Forests: 

A Literature Review 

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Block, William M.; Finch, Deborah M., technical editors. 1997. Songbird ecology in 

southwestern ponderosa pine forests: a literature review. Gen. Tech. Rep. RM-GTR-292. 

Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest 

and Range Experiment Station. 152 p. 

This publication reviews and synthesizes the literature about ponderosa pine forests of 

the Southwest, with emphasis on the biology, ecology, and conservation of songbirds. 

Critical bird-habitat management issues related to succession, snags, old growth, fire, 

logging, grazing, recreation, and landscape scale are addressed. Overviews of the ecology, current use, and history of Southwestern ponderosa pine forests are also provided. 

This report is one of the outcomes of the Silver vs ~hom'as court-settlement agreement 

of 1996. It is intended for planners, scientists, and conservationists in solving some of 

the controversies over managing forests and birds in the Southwest. 

Keywords: ponderosa pine, Southwest, songbirds 

Technical Editors: 

The order of editorship was determined by coin toss. William M. Block is project leader 

and research wildlife biologist with the Southwestern Terrestrial Ecosystem research work 

unit, Southwest Forest Sciences Complex, 2500 S. Pine Knoll, Flagstaff, AZ 86001. Deborah 

M. Finch is project leader and research wildlife biologist with the Southwestern Grassland 

and Riparian research work unit, Forestry Sciences Laboratory, 2205 Columbia SE, 

Albuquerque, NM 871 06. 

Publisher: 

Rocky Mountain Forest and Range Experiment Station 

Fort Collins, Colorado 

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May 1997 

Front Cover: Grace's warbler, pygmy nuthatch, and violet-green swallow. 

Artwork by Joyce Patterson. 
Songbird Ecology in 

Southwestern Ponderosa 

Pine Forests: 

A Literature Review 

William M. Block and Deborah M. Finch 

Technical Editors 

Contents 

Preface ..................................................... i i 

TheAuthors .................................................. iii 

Introduction .................................................. 1 

Deborah M. Finch and William M. Block 

Chapter 1 

Ecology of Southwestern Ponderosa Pine Forests .................... 3 

~illiam H. Moir, Brian W Geils, Mary Ann Benoit, and Dan Scurlock 

Chapter 2 

Contemporary Human Use of Southwestern Ponderosa Pine Forests . . 

Carol Raish, Wang Yong, and John M. Marzluff 

Chapter 3 

A Historical Overview ........................................ 

Dan Scurlock and Deborah M. Finch 

Chapter 4 

Songbird Status and Roles. ................................... 

Linnea S. Hall, Michael L. Morrison, and William M. Block 

Chapter 5 

Effects of Urbanization and Recreation on Songbirds ............... 

John M. Marzluff 

Chapter 6 

Effects and Interactions of Fire, Logging, and Grazing .............. 

Deborah M. Finch, Joseph L. Ganey, Wang Yong, Rebecca T: Kimball, 

and Rex Sallabanks 

Chapter 7 

Landscape Dynamics and Considerations ........................ 

Kevin M. Rich and Patricia Mehlhop 

Chapter 8 

Summary ..................................................... 145 

William M. Block, Deborah M. Finch, Joseph L. Ganey, and William H. Moir 

Appendix: Birds Referenced in This Book. .......................... 151 
Preface 

Denver P. Burns 

As part of a settlement agreement related to the Silver 

us. Thomas (1996) litigation, the Rocky Mountain Forest 

and Range Experiment Station agreed to summarize the 

current knowledge on songbirds inhabiting ponderosa 

pine forests in the Southwest. This review represents the 

state-of-knowledge of songbird ecology in Southwestern 

ponderosa pine forests. 

Ponderosa pine is the major forest type in the Southwest, encompassing over 3 million hectares. rhe forest belt 

extending above the Mogollon Rim is the largest contiguous ponderosa pine forest in the world. These forests have 

been occupied by humans for thousands of years, during 

which time humans derived multiple benefits from a variety of resources. Not only have these forests provided 

human needs, but they also provide for the needs of numerous plants and animals. 

A group of animals of particular interest are the songbirds, which occupy numerous habitats and stages. Each 

species uses a unique combination of habitat conditions, and 

changes to the forest may influence that species' population 

status. To a certain extent, birds can act as indicators of environmental conditions. By examining trends in bird populations, one might hope to index forest health, and vice versa. 

Thus, understanding the ecology of birds in ponderosa 

pine forest, including their habitat requirements and population trends, is key to gauging health of this forested ecosystem. The chapters presented in this document summarize what we know about ponderosa pine forest 

ecology as well as about the birds that inhabitat those forests. They represent a compilation of numerous independent studies and provide a springboard for the development of new studies. The information presented herein 

may also be used to assess current management direction 

for these forests and to fine-tune management to more 

effectively provide conditions to sustain populations of 

the native ponderosa pine avifauna well into the future. 

The information provided in this document represents 

independent contributions by biologists, ecologists, and 

social scientists that summarize and synthesize current 

knowledge about ponderosa pine songbirds, including the 

ecology and use of these forests. Because topics presented 

in these chapters were broadly overlapping, some redundancy in materials present was unavoidable. I must also 

acknowldge the valuable contribution of reviewers to 

improving this document. Peer reviews were solicited for &. 

each chapter, and the entire document underwent rigorous blind review from three professional societies: American Ornithologists' Union, Cooper Ornithological Society, 

and The Wildlife Society. Collectively, these reviews provided a quality check, and response to revew comments 

resulted in a quality document. 

USDA Forest Service Gen. Tech Rep. RM-GTR-292. 1997 
ships, conservation biology, and the effects of land-manThe Authors agement practices on native wildlife. 

Mary Ann Benoit (chapter 1) is a zone wildlife biologist 

for the USDA Forest Service, Region 3, on the Coconino 

National Forest. She earned a B.S. in biology from Northern Arizona University and a B.A. in interior design from 

Mount Vernon College. Benoit currently serves as the biologist and GIS/database manager on the West and East 

Clear Creek Ecosystem Management Projects. Her research interests include wildlife habitat relationships in 

forested ecosystems, effects of forest management practices on wildlife, and geographic information systems. 

William M. Block (chapters 4 and 8) is project leader and 

research wildlife biologist of the Southwestern Terrestrial 

Ecosystem research work unit in Flagstaff, Arizona, and 

leader of the Mexican Spotted Owl Recovery Team. He has 

been with the USDA Forest Service's Rocky Mountain Forest and Range Experiment Station since 1990. He received 

his Ph.D. from the University of California, Berkeley in wildland resource sciences; his M.S. in wildlife from Humboldt 

State University; a B.A. in economics from California State 

University, San Diego; and a B.S. in wildlife from Michigan 

State University. His current research interests include, and 

he has published widely on, avian ecology, vertebrate-habitat relationships, community ecology, threatened and endangered species, and the development of conservation plans. 

Deborah M. Finch (chapters 3,6, and 8) is project leader 

and research wildlife biologist of the Southwestern Grassland Watersheds research work unit and team leader of 

the Middle Rio Grande Ecosystem Program research work 

unit in Albuquerque, New Mexico. Finch has been with the 

USDA Forest Service's Rocky Mountain Forest and Range 

Experiment Station since 1978. She graduated with a B.S. in 

wildlife management from Humboldt State University; an 

M.S. in zoology from Arizona State University; and a Ph.D. 

in zoology and physiology from the University of Wyoming. 

Her interests include avian reproductive ecology; bird and 

mammal habitat relationships; threatened, endangered and 

sensitive species; and technology transfer. 

Joseph L. Ganey (chapters 6 and 8) is a research wildlife 

biologist with the Terrestrial Ecosystems research work 

unit located in Flagstaff, Arizona. He has been with the 

USDA Forest Service's Rocky Mountain Forest and Range 

Experiment Station since 1991. He received a B.S. in wildlife management from Humboldt State University; an M.S. 

in biology from Northern Arizona University; and a Ph.D. 

in zoology from Northern Arizona University. He has 

worked on ecology and habitat relationships of the Mexican spotted owl for the past 13 years. His general research 

interests include avian ecology, wildlife habitat relationBrian W. Geils (chapter 1) is a research plant pathologist 

for the USDA Forest Service's Rocky Mountain Forest and 

Range Experiment Station in Flagstaff, Arizona. He has a 

B.S. in wildlife biology from Utah State University; a MS. 

in forest science from the University of Idaho; and a Ph.D. 

in botany-plant pathology from Colorado State University. Geils' current work addresses the impacts of natural 

disturbance agents on western conifers. His research interests include the ecological effects, spread, and intensification of dwarf mistletoe, the distribution and epidemiology 

of stem rust in pine, and development of survey methods 

and spatial models for describing interactions among dwarf 

mistletoe, stem rust, root disease, and other natural disturbance agents in coniferous forests of the Rocky Mountains. 

Linnea S. Hall (chapter 4) is assistant professor of wildlife biology/avian ecology in the Department of Biological Sciences, California State University, Sacramento. Hall 

received her Ph.D. in wildlife ecology from the University 

of Arizona, where she studied the elegant trogon for her dissertation, and helped implement a monitoring program for 

neotropical migrant birds on lands administered by the Forest Service. Her research background includes publications 

in bird population trends and habitat use; ecology and physiology of rodents; and habitat use of amphibians and reptiles. Her current research involves studies of neotropical 

migrant birds, rodent ecology, and habitat quality. 

Rebecca T. Kimball (chapter 6) is a lecturer and research 

assistant professor in the Department of Biology at the 

University of New Mexico. She received her B.A. from 

Dartmouth College in 1985 with a degree in biology. Following that, Kimball took courses at the University of 

Michigan's Biological Station and at the University of Utah. 

She completed graduate work at the University of New 

Mexico where she received her Ph.D. in biology in 1995. Her 

interests are in avian ecology and evolution, and she has 

conducted research on reproductive behavior, basic ecology, 

morphological relationships and phylogenetics of birds. 

John M. Marzluff (chapters 2 and 5) is the senior scientist 

at the Sustainable Ecosystems Institute in Meridian, Idaho. 

He has a B.S. in wildlife biology from the University of 

Montana and a M.S. and Ph.D. from Northern Arizona 

University. Marzluff has spent the last four years on the 

U. S. Fish and Wildlife Service's Hawaiian Crow Recovery Team. His research interests include the effects of silviculture on nest predators and raptors, crow and raven 

ecology, vertebrate habitat relationships, effects of urbanization on bird populations, conservation of endangered 

species on island ecosystems, and captive propagation and 

reintroduction. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 iii 
Patricia Mehlhop (chapter 7) is director of the New 

Mexico Natural Heritage Program at the University of 

New Mexico and a research scientist with The Nature 

Conservancy, specializing in animal ecology. She graduated with a B.S. and M.S. in zoology from the University 

of Maryland and with a Ph.D. in biology from the University of New Mexico. Her research interests include 

animal habitat relationships, animal community ecology, 

and rare species conservation. Current research includes 

a study of habitat patch use by migrating and breeding 

birds in small montane "islands" of the Southwest and 

conservation designs at regional scales. 

William H. Moir (chapters 1 and 8) is a research ecologist 

for the USDA Forest Service's Rocky Mountain Forest and 

Range Experiment Station in Flagstaff, Arizona. Before his 

present position, Moir was a regional ecologist for Region 

3 in Albuquerque, New Mexico. Moir earned a B.S. in 

physics from Purdue University, a M.S. in biology from 

New Mexico State University, and a Ph.D. in botany and 

soils from Washington State University. His research interests include overstory/understory relationships, habitat types, succession, and fire ecology. 

Michael L. Morrison (chapter 4) is adjunct professor of 

wildlife biology in the Department of Biological Sciences, 

California State University, Sacramento, and in the School 

of Renewable Natural Resources, University of Arizona, 

Tucson. He received a B.S. in zoology from Northern Arizona University; an M.S. in wildlife science from Texas 

A&M; and a Ph.D. in wildlife ecology from Oregon State 

University. He has published widely on habitat relationships of terrestrial vertebrates, including studies of bird 

foraging behavior, population trends, and the influence 

of land-use practices. He is senior author of the book Wildlife-Habitat Relationships: Concepts and Applications (with B. 

G. Marcot and R. W. Mannan), published by the University of Wisconsin Press (1992), and has edited or co-edited several other works on foraging ecology and habitat 

relationships. He is currently working with various public and private organizations on environmental impact 

assessment, studies of sensitive species, and development 

of habitat restoration plans. 

Carol Raish (chapter 2) is a research social scientist with 

the USDA Forest Service's Rocky Mountain Forest and 

Range Experiment Station in Albuquerque, New Mexico. 

She received a B.A. degree in Spanish from Washburn 

University; an M.A. in anthropology from the University 

of Nebraska; and a Ph.D. in archeology from the University of New Mexico. Her current research interests focus 

on intercultural conflict and reassertion of cultural identity among indigenous and traditional groups and on the 

economic, social, and cultural contributions of traditional 

stockraising operations. Prior to joining the Rocky Mountain Station in 1995, Carol served as Heritage Resource Staff 

on the Jemez Ranger District, Santa Fe National Forest. 

Kevin M. Rich (chapter 7) is a research assistant at the 

New Mexico Natural Heritage Program, where he is working with staff from the Arizona Game and Fish Department, the Navajo Natural Heritage Program, and The 

Nature Conservancy to develop a conservation strategy 

for the Arizona-New Mexico Mountains Ecoregion. He 

also is atPh.D. candidate at the University of New Mexico 

studying conservation biology and ecosystem management 

with Dr. James H. Brown. He received a B.S. in biology with 

distinction from Stanford University and has worked as a 

Museum Technician at the Smithsonian Institution's National 

Museum of Natural History and as a Senior Conservation 

Systems Specialist at The Nature Conservancy. 

Rex Sallabanks (chapter 6) is senior research biologist with 

the Sustainable Ecosystems Institute (SEI) in Meridian, Idaho. 

Rex has been with the Institute for three years. He graduated from the University of Plymouth in the United Kingdom in 1987 with a B.S. in ecology and conservation biology 

and a Ph.D. from the University of Oregon in 1992. Prior to 

his position with SEI, Rex was a postdoctoral research associate at the North Carolina State University where he studied the effects of fragmentation of bottomland hardwood 

forests on breeding songbird communities. His current research projects focus on the effects of forest management, 

fragmentation, and wildfire on bird communities in the inland Pacific Northwest. Rex is the co-editor (with John 

Marzluff) of the forthcoming book, Avian Conservation: Research and kbIfZgemenf, to be published by Island Press. 

Dan Scurlock (chapters 1 and 3) is a consulting environmental historian and naturalist. He has worked for universities, public schools, government agencies, private 

organizations, and businesses as a researcher, instructor, 

planner, writer, photographer, and trip leader for 30 years 

in the American Southwest, Mexico, and Canada. His more 

than 70 academic and popular publications in history, archaeology, architectural history, and natural history range 

from articles to book-length reports. He holds an A.B.S. 

in science and B.A. and M.A. degrees in anthropology. 

Wang Yong (chapters 2 and 6) is a forest and wildlife research associate at the University of Rhode Island. He 

worked as a post-doctoral visiting wildlife biologist from 

1994 to 1996 at the USDA Forest Service's Rocky Mountain Forest and Range Experiment Station in Albuquerque, New Mexico. He graduated with a B.S. in biology 

from Shanghai Normal university and a Ph.D. in biology 

from the University of Southern Mississippi. His research 

interests include wildlife conservation, animal physiological ecology, avian migration, wildlife population dynamics, and research design and statistics. 

* 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Deborah M. Finch and William M. Block 

This book reviews and synthesizes the diverse literature about ponderosa pine forests of the Southwest, emphasizing the biology and ecology of songbirds in relation to habitat changes resulting from natural events such 

as succession and fire, and management activities such as 

logging, grazing, and recreation. This product is one of 

the outcomes of a 1996 court-ordered settlement agreement pertaining to protection of the Mexican spotted owl 

(Strix occidentalis lucida) that included a section requiring 

a report on the habitat requirements of and threats to songbirds inhabiting Southwestern ponderosa pine. This book 

fulfills those objectives by emphasizing critical habitat issues and identifying bird species that may be sensitive to 

changes in availability of habitat types, structures, sera1 

stages, and special features such as snags, aspen and oak, 

and old trees. 

To write the chapters, we assembled a team of experts 

from a cross-section of disciplines representing forestry, 

plant ecology, avian biology and ecology, endangered species conservation, environmental history, and social sciences. Biographical sketches of authors are included at 

the beginning of the book. Authors were instructed to address all passerines as well as doves, hummingbirds, and 

woodpeckers; that is, birds with sizes and behavioral responses to habitats and spatial scales that were deemed relatively similar to passerines. A comprehensive list of common and scientific names of birds known to occupy 

Southwestern ponderosa pine forests is in Appendix A. 

Blind reviews for the entire book were obtained from 

three professional societies: The Wildlife Society, the 

American Ornithologists' Union, and the Cooper Ornithological Society. Blind reviews were sought to strengthen 

manuscripts and establish the book's authority. 

The book starts with a chapter that summarizes the state 

of knowledge of the geography, ecology and diversity of 

Southwestern ponderosa pine forests. Chapter 1 highlights 

the complexity and range of variation of contemporary 

Southwestern forests and sets the stage for more specialized chapters. Current human uses of Southwestern ponderosa pine forests are described in Chapter 2. An understanding of how current forests are managed and how 

such management may alter environmental conditions is 

important to identify the principal causes of changes in 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 

songbird habitats and songbird populations. Chapter 3, 

an environmental history of Southwestern ponderosa 

pine, establishes reference conditions and an understanding: of past human activities that may have influenced 

what we think and see today. This chapter also includes a 

discussion of prehistoric and historic human uses of birds, 

avian archaelogical findings, and avifaunal accounts and 

checklists by early ornithologists. Such information is a 

useful reminder of how our knowledge of Southwestern 

ponderosa pine and its avifauna has evolved. 

Chapter 4 launches the ornithological expedition to the 

heart of the book by summarizing the general biology and 

habitat use of songbirds found in Southwestern ponderosa pine forests. This chapter clarifies the basic patterns 

of habitat use by different species and groups of birds and 

identifies habitat elements of high management priority. 

Chapter 5 is a thought-provoking review and analysis of 

the effects of urbanization and recreation on birds of ponderosa pine. This chapter is an example of the emerging 

body of literature that seeks to evaluate direct and indirect impacts of human population growth on wildlife. The 

subject of land management effects on songbirds, with a 

focus on fire, logging, and grazing, is tackled in Chapter 

6. Because different kinds of land management are frequently practiced simultaneously, their interactions and 

effects are difficult to interpret. However, the authors rise 

to the occasion with an exhaustive discussion and interpretation of issues. Chapter 7 is a landscape overview of 

issues identified in previous chapters and ends with a plea 

for more studies at the landscape level. The book ends 

with a summary of key issues and a call for more research, 

especially research of an experimental nature. 

In conclusion, the editors and authors of this book have 

compiled a comprehensive review of the literature on the 

topic of Southwestern ponderosa pine forests and its songbird inhabitants. We hope that this publication will be a 

useful source of information for natural resource managers, scientists, and environmentalists and will supply the 

basis for new standards in research and management. In 

addition, we hope that this review will help to solve some 

of the controversies pertaining to management of forests 

and birds in the Southwest. 
Acknowledgments 

We thank the Publications Office of the Rocky Mountain Forest and Range Experiment Station, especially 

Madelyn Dillon and Lane Eskew, for their patience in handling the time-sensitive editorial work on this book. We 

thank Bob Dana for conducting electronic literature 

searches for various chapters and Mike Means and Brenda 

Strohmeyer for tracking down references. We are grateful 

to Nora Altamirano for formatting the manuscripts according to Station guidelines. The Southwestern Region 

(Region 3) of the USDA Forest Service supplied financial 

support for the writing and publication of this product. 

We thank all authors for their contributions and patience, 

and finally we thank Denver Burns, Station Director, for 

suggesting that we coordinate this project. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 1 

Ecology of Southwestern Ponderosa Pine Forests 

William H. Moir, Brian Geils, Mary Ann Benoit, and Dan Scurlock 

What Is Ponderosa Pine Forest 

and Why Is It Important? 

Forests dominated by ponderosa pine (Pinus ponderosa 

var. scopulorurn) are a major forest type of western North 

America (figure 1; Steele 1988; Daubenmire 1978; Oliver 

and Ryker 1990). In this publication, a ponderosa pine 

forest has an overstory, regardless of successional stage, 

dominated by ponderosa pine. This definition corresponds 

to the interior ponderosa pine cover type of the Society of 

American Foresters (Eyre 1980). At lower elevations in the 

mountainous West, ponderosa pine forests are generally 

bordered by grasslands, pinyon-juniper woodlands, or 

chaparral (shrublands). The ecotone may be wide or narrow, and a ponderosa pine forest is recognized when the 

overstory contains at least 5 percent ponderosa pine (USFS 

1986). At upper elevations ponderosa pine forests usually 

adjoin or grade into mixed conifer forests. A mixed conifer stand where ponderosa pine has more overstory 

canopy than any other tree species or there is a plurality 

of tree stocking, is an interior ponderosa pine forest (Eyre 

1980). 

Two distinct ponderosa pine forests occur in the Southwest. The xerophytic (drier) forests have ponderosa pine 

as a climax tree (reproducing successfully in mid- to late 

succession) and comprise the ponderosa pine life zone 

(transition or lower montane forest) (USFS 1991; DickPeddie 1993). The mesophytic (wetter) forests have ponderosa pine as a sera1 tree (regeneration occurs only in 

early- to mid-succession although older trees may persist 

into late succession) and are part of the mixed conifer life 

zone or upper montane forest (USFS 1991; Dick-Peddie 

1993). 

Ponderosa pine forests are important because of their 

wide distribution (figure I), commercial value, and because they provide habitat for many plants and animals. 

Ponderosa pine forests are noted for their variety of passerine birds resulting from variation in forest composition and structure modified by past and present human 

use. Subsequent chapters discuss how ponderosa pine 

forests are associated with different types and number of 

passerine birds and how humans have modified these 

forests and affected its occupancy and use by passerine 

birds. This chapter discusses the ecology and dynamics 

of ponderosa pine forests and wildlife use in general and 

describes natural and human induced changes in the composition and structure of these forests. 

Paleoecology 

The oldest remains of ponderosa pine in the Western 

United States are 600,000 year old fossils found in west 

central Nevada. Examination of pack rat middens in New 

Mexico and Texas, shows that ponderosa pine was absent 

during the Wisconsin period (about 10,400 to 43,000 years 

ago), although pinyon-juniper woodlands and mixed conifer forests were extensive (Betancourt 1990). From the 

late Pleistocene epoch (24,000 years ago) to the end of the 

last ice age (about 10,400 years ago), the vegetation of the 

Colorado Plateau moved southward or northward with 

glacial advance or retreat. Regional temperatures over the 

Southwest during the glacial advances may have been 6 "C 

lower and annual precipitation 220 mm higher in the lowlands than today. Ponderosa pine in the mountains of New 

Mexico occurred about 400 m lower than where it is found 

today (Dick-Peddie 1993; Murphy 1994). 

With the beginning of warming in the early Holocene, 

ponderosa pine began colonization of the Colorado Plateau. Pinyon-juniper woodlands shifted upward and 

northward from a low elevation of just over 450 m to 1,500 

m. Pinyon pine edulis) reached its present upper limit 

(about 2,100 m) between 4,000 and 6,000 years ago. The 

present distribution of ponderosa pine forests in the interior West and Southwest was apparently the result of this 

rapid Holocene expansion, but the exact cause and manner of this expansion is unknown (Anderson 1989; 

Betancourt 1987). 

Climate and Soils 

Climates in ponderosa pine forests are similar throughout the interior Western United States. For example, a comparison of climates at Spokane, Washington and Flagstaff, 

Arizona where ponderosa pine forests occur with a grassy 

understory, shows that levels of mean annual precipitation (MAP) at Spokane is 41 cm and at Flagstaff is 57 cm. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Figure 1. Distribution of ponderosa pine in North America. Arizona and New Mexico comprise the Southwest area 

discussed in this chapter (Little 1971). 

4 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Ecology of Southwestern Ponderosa Pine Forests 

Both locations have a pronounced dry season during several warm months when precipitation is insufficient to 

maintain plant growth. This drought is in July and August at Spokane and May and June at Flagstaff. 

Climates of Arizona and New Mexico are described in 

the General Ecosystem Survey (USFS 1991; table 1). Ponderosa pine forests mostly occur within the High Sun Cold 

(HSC) and High Sun Mild (HSM) climate zones (table 1). 

Mean annual air temperatures (MAAT) for xerophytic and 

mesophytic forests are 9 "C and 6 "C in the HSM zone, 

and 5 to 7 "C and 4 "C the HSC zone, respectively (table 1). 

For these climate zones, mean annual precipitation (MAP) 

is 520 to 560 mm and 660 mm, respectively (table 1). The 

climate (figure 2a) for xerophytic forests of ponderosa 

pine/Arizona fescue (PIPO/FEAR) is near the mid-range 

of MAAT and MAP at Flagstaff (FLA), Pinetop (PIN), and 

Ruidoso (RUI). In contrast, ponderosa pine/blue grama 

(PIPO/BOGR) forests at Los Alarnos (LOS) are near the lower 

limit of MAP, and forests of ponderosa pine/silverleaf oak 

(PIPO/QUHY) at Mt. Lernmon (MTL) are near the upper 

limit of MAP. Ponderosa pine/Arizona white oak (PIPO/ 

QUAR) forests at Payson (PAY) have the warmest MAAT 

and ponderosa pine/mountain muhly (PIPO/MUMO) forests around Jacob Lake (JAC) have the coldest MAAT. 

The soil moisture regime (SMR) of xerophytic Forests is 

ustic (dry) (USFS 1991). At the stations examined (figures 

2b-f), seasonal drought is most severe in May and June 

and understory vegetation, mostly grasses, becomes dry 

and flammable. Relationships between fire and climate 

in the Southwest have been studied by Swetnam and colleagues (Swetnam 1990; Swetnam and Baisan 1996; 

Swetnam and Betancourt 1990). The SMR of mesophytic 

forests is udic (wet) (USFS 1991); in these forests there is 

no drought in upper soil horizons during the average 

growing season. Therefore, at higher elevations where 

ponderosa pine is a seral tree of mixed conifer forests, the 

growing season precipitation is usually sufficient to maintain plant growth. 

The soil temperature regime (STR) of ponderosa pine 

forests in Arizona and New Mexico is generally frigid; in 

the southern portions of these states at lower elevations it 

is mesic (USFS 1991). This shift to warmer soils, coincident with May through June droughts, is indicated by an 

understory vegetation of broadleafed, evergreen species 

such as Emory, gray, wavyleaf and silverleaf oaks (Quercus 

emoryi, Q, grisea, Q. undulata, Q. hypoleucoides), manzanita 

(Arctostaphylos pungens), madrones (Arbutus xalapensis, A. 

arizonica), yuccas (Yucca spp.), and other shrubs and trees 

(table 1). Although Arizona pine (Pinus arizonica) replaces 

P. pdnderosa on some mesic soils in southeastern Arizona, 

forest dynamics and structure are similar. 

The distinction between xerophytic and mesophytic 

zones is essential to understand plant succession in ponderosa pine forests in the Southwest. Beschta (1976) described the climate of a single ponderosa pine type in central Arizona without differentiating the ustic zone, where 

the pine is climax, from the udic zone, where it is seral. 

Similarly, both zones were combined in early forest inventories in Arizona and New Mexico (Eyre 1980; choate 

1966; Spencer 1966) and showed considerably more ponderosa pine cover type than there is today (Johnson 1994). 

Winter snow storms do occur in Southwestern ponderosa pine forests. In central Arizona annual snowfall 

ranges from 130 to 250 mm for the ponderosa pine zone 

to about 250 to 320 mm in the mixed conifer zone (Beschta 

1976). South of the Mogollon Rim, the average annual 

snowfall is estimated at 90 to 165 mm, but reliable snow 

measurements are unavailable. 

Vegetation 

Xerophytic Forests 

In the lower montane zone at elevations 2,150 to 2,600 

m (elevations vary according to latitude and local conditions), there are 37 ponderosa pine forest types based on 

associated understory vegetation (Dick-Peddie 1993; Moir 

Table 1. Summary of climates of Southwestern ponderosa pine forests (USFS 1991). 

MAAT("C) MAP (mm) 

Six-month season with Winter Climate Vegetation 

more than 112 annual precip. temp. category indicators XERO MESO XERO MESO 

High sun (HS) Apr 1 to Sep 30 Mild (M) HSM QUGR, QUEM 9 6 600 700 

High sun (HS) Apr 1 to Sep 30 Cold (C) HSC PIED, QUGA 5-7 4 520-560 660 

Low sun (LS) Oct 1 to Mar 30 Mild (M) LSM PICA, QUUN 9 7 600 700 

Low sun (LS) Oct 1 to Mar 30 Cold (C) LSC ARTR 5-7 4 480-560 660 

ARTR = Artemisia tridentata PICA = Pinus californiarum MAAT = mean annual air temp 

PIED = Pinus edulis QUGA = Quercus gambelii MAP = mean annual precipation 

QUGR = Quercus grisea QUUN = Quercus undulata XERO = xerophytic forests 

QUEM = Quercus emoryi MESO = mesophytc forest 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 1 

Xerophytic ponderosa pine climate 

Precipitation/temperature summary Payson (PAY) 1498 m Mean Temp 

Mean Pncip 

Total precip = 553 mm 

Avg temp = 13.1 C 9 

w 

P 

i FLA / PIP0,&0 ! I 

i JAC 8 I 

Avg annual preclpltatlon (mm) (MAP) 

600 

- 

120 

E 

- E 

Total precip = 678 mm P 

6 

400 

P 

80 c t 

B 

. - 

- d 

200% 

40 e 

a 

2 

0 0 12 

Month Month 

c) 

/ Flagstaff (FLA) 2135 m 

Avg temp = 6.8 C 

1 12 

Total precip = 564 mm 

Avg temp - 7.7 C 

OC i, I ,A 

Month 

e) 

Month 

f) 

Figure 2. Climate summaries for xerophytic ponderosa pine in North America. PIPO, ponderosa pine; QUAR, Arizona white oak; 

BOGR, blue grama; FEAR, Arizona fescue; QUHL: silverleaf oak; MUMO, mountain muhly; PAL: Payson; LOS, Los Alamos; 

RUI, Ruidoso; PIN, Pinetop; MTL, Mt. Lemmon; FLA, Flagstaff; JAC, Jacob Lake. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Ecology of Southwestern Ponderosa Pine Forests 

and Fletcher 1996; USFS 1986,1987a, 198%). These types 

can be combined into 3 major groups, based on similarities in structure, composition, and fire response. 

The fringe pine forest types are at dry, warm, lower elevations where ponderosa pine occurs with woody species that are common in the adjoining pinyon/juniper and 

pinyon/oak/juniper woodlands. Depending on geographic location, typical associated species are P. edulis, P. 

discolor, P. californiarurn, Juniperus spp., Quercus grisea, Q. 

arizonica, Q. emoryi, Arctostaphylos pungens, Artemisia 

tridentata, and Chrysothamnus nauseosus. Associated trees 

form a mid-level canopy layer below the ponderosa pine 

overstory (Marshall 1957). These additional species provide resources for a wide variety of animals; discussed in 

the wildlife section of this chapter. Blue grama (Bouteloua 

gracilis) is a diagnostic species, and ponderosa pine/blue 

grama has widespread forest association throughout the 

Southwest (USFS 1986). 

Where precipitation is greater than about 480 mm, blue 

grama is absent or minor and ponderosa pine occurs with 

understory bunchgrass species, mainly Festuca arizonica, 

Muhlenbergia montana, and/or M. virescens. There may be 

a mid-level canopy of shrubs, copses of oaks, or even an 

occasional oak tree (Kruse 1992), but these are minor vegetation components. Fires, either lightning- or humancaused, are frequent in these dry forests. Southwestern 

pine forests can be grouped with ponderosa pine forests 

in other areas of in the Western United States that share a 

similar fire ecology. Southwestern ponderosa pine/bunchgrass forests are similar to warm, dry forests in Idaho, 

Montana, and Utah (Davis et al. 1980; Crane and Fischer 

1986; Fischer and Bradley 1987; Bradley et al. 1992). Numerous descriptions of presettlement forests in the Southwest (Woolsey 1911; reviews Cooper 1960; Covington and 

Moore 1994; Moir and Dieterich 1988) apply to this group 

of forests. 

The third group of xerophytic ponderosa pine forests 

are those with understories dominated by shrubs and midlevel trees. Bunchgrasses may still be abundant, especially 

as patches in open areas. Common woody associates include Quercus gambelii, Q. undulata, Robinia neomexicana, 

Cercocarpus montana, and Symphoricarpos oreophilus. These 

forests are similar in structure and fire responses to the 

warm, moist ponderosa forests of central Idaho and Utah 

(Crane and Fischer 1986; Bradley et al. 1992). 

Mesophytic Forests 

In mesophytic forests at elevations 2,400 to 3,000 m (elevations vary according to latitude and local conditions), 

ponderosa pine is a major sera1 tree in 11 forest associations (USFS 1986, 1987a). These forests are identified by 

increasing importance of Pseudotsuga menziesii (Douglasfir), Abies concolor (white fir), Picea pungens (blue spruce), 

and Pinus strobiformis (Southwestern white pine) as climax trees (Dick-Peddie 1993; USFS 1986,1987a, 198%; figure 3). Thousands of hectares of ponderosa pine-dominated mixed conifer forest existed in the Southwest in the 

early- to mid-20th century and were inventoried as part 

of the ponderosa pine cover type (johnson 1993,1994; Eyre 

1980). Ponderosa pine and the other conifers were often 

associated with aspen (Populus tremuloides), which occurs 

where previous fires favored its regeneration (Jones 1974; 

Abolt et al. 1995). Without recurring fires, however, conifers !eventually replace aspen (Moir and Ludwig 1979; 

Dick-Peddie 1993). The aspen and coniferous mesophytic 

forests of the Southwest have structures and fire responses 

similar to those of mesic forests in the central and northem Rocky Mountains (Crane and Fischer 1986; Fischer and 

Bradley 1987, Bradley et al. 1992). 

A number of mesophytic forest types in the Southwest 

include a bunchgrass understory of Festuca arizonica, 

Muhlenbergia montana, and/or M. virescens. In these types, 

ponderosa pine, Douglas-fir, and sometimes Southwestern white pine are the most important trees. The occasional white fir or blue spruce in these forests are evidence 

of the udic soil depicted in figure 3. Counterparts in westem Montana and central Idaho are the warm, dry Douglas-fir forest types (Fischer and Bradley 1987; Crane and 

Fischer 1986). 

Ponderosa pine and other conifers also occur with an 

understory of shrubs or mid-level trees such as Quercus 

gambelii, Robinia neomexicana, Symphoricarpos oreophila, 

Holodiscus dumosus, or Salix scouleriana (for more complete 

lists of associated species see Moir and Ludwig 1979). 

Rather than bunchgrasses, the herbaceous layer is composed of mesic species such as Bromus richardsonii, Artemisia fianserioides, Osmorhiza chilensis, Geranium richardsonii, and Viola canadensis. Similar forests of moist 

Douglas-fir occur in Idaho (Crane and Fischer 1986), westem Montana (Fischer and Clayton 1983), and Utah (Fischer 

and Bradley 1987; Bradley et al. 1992). 

Finally, there are mixed conifer forests in the Southwest 

where ponderosa pine is minor or absent. These are the 

cold coniferous forests (Dick-Peddie 1993; USFS 1986, 

1987a, 198%) where stand-replacing fires favor regeneration to aspen or tall shrubs such as Acer glabrum, Salix 

scouleriana, or Holodiscus dumosus. The coniferous species 

of these forests are Douglas-fir, white fir, blue spruce, 

Southwestern white pine, and sometimes bristlecone pine 

(Pinus aristata). 

Fire 

In the last decade forest fires have increased in Arizona 

and New Mexico (figure 4). Fire, the most important natural abiotic disturbance in ponderosa pine forests (Moir and 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 1 

Dry (ustic) soil Wet (udic) soil 

4 - 

Dry (ustic) soil Wet (udic) soil 

Fir and spruce 

Pine 

Figure 3. Generalized climate-differentiated ponderosa pine forests in Arizona and New Mexico. Diagram a) depicts the open, grassy 

pine forests described around the turn of the century (1890 to 1925). The open forest has a grassy understory, sparse 

ponderosa pine regeneration in the dry end, and, as precipitation increases, poor regeneration of ponderosa pine, Douglasfir, blue spruce, or white fir. Diagram b) illustrates the same forest under average conditions in the 1990s (Johnson 1993, 

1994). Diagram c) depicts the same forest 10 to 15 years after a fire holocaust. Natural or managed reforestation is occurring, 

although understory grasses may not be the same composition or density as that in diagram a) (Foxx 1996). Artwork by 

Joyce Patterson. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Ecology of Southwestern Ponderosa Pine Forests 

Dieterich 1988; Moody et al. 1992; Covington and Moore 

1994), determines plant composition, succession, and forest structure. Fire ecology, especially since the 1930s and 

in the xerophytic ponderosa pine/bunchgrass forests, is 

well studied (Weaver 1943 and 1967; Biswell 1972; Cooper 1960; Ahlgren and Ahlgren 1960; Biswell et al. 1973; 

Habeck and Mutch 1973; Wright 1978; Moir and Dieterich 

1988; Morgan 1994; Pyne 1996; Allen 1996). Forest succession under different fire regimes is generalized in the papers cited above and should be considered as hypotheses. 

Although they present sequences of species replacement 

and stand structure, these models generally do not specify 

the time between stages. 

Frequent, low-intensity fires were part of the ecology 

and evolutionary history of ponderosa pine forests. Crown 

fires seldom occurred or were confined to small thickets 

(Woolsey 1911; Pyne 1996). Fires in the xerophytic pine 

forests occurred every 2 to 12 years and maintained an 

open canopy structure and a variable, patchy tree distribution (White 1985; Cooper 1961; Covington and Moore 

1994; figure 3). The open, patchy tree distribution from 

fires and other disturbances, such as bark beetles and 

mistletoe, reduced the risk of fire holocausts. Downed 

woody material was sparse, and fires before about 1890 

were fueled mostly by herbaceous material that accumulated at the end of the annual drought period. These lowintensity, surface fires reduced ground fuel, thinned 

smaller trees, and invigorated the understory maintaining the open forest structure (Ahlgren and Ahlgren 1960; 

Ffolliott et al. 1977). 

Understory burns occurring over millennia helped forest vegetation adapt to fire (Habeck and Mutch 1973; Rapport and Yazvenko 1996). For example, the thick, corky 

bark of mature (15 to 20 cm diameter at breast height [dbh]) 

ponderosa pine and Douglas-fir insulates the cambium 

Year 

A 

20- a!... -- - . - A'? 

A ,Au -40 : 4 kA *A 

Figure 4. Forest fires in Arizona and New Mexico, 191 0-1 995 

(US. Department of Agriculture, Forest Service, 

Southwest Region). 

A lo------ 

AdA 

C 

01 

from killing temperatures. Another adaptation to fire, as 

well as drought, is the longevity of seed trees. Successful 

tree reproduction occurs only when heavy seed crops and 

germination coincide with moist springs and summers 

and a long fire-free period (Pearson 1950). Because these 

factors only occasionally occur simultaneously, tree reproduction is episodic. Decades may pass before conditions 

for reproduction and seedling survival are favorable 

(White 1985). However, ponderosa pine and Douglas-fir 

areilong-lived (4 to 5 centuries) and over that time numerous opportunities for reproduction and establishment 

exist (Pearson 1950). Although ponderosa pine and Douglas-fir have high genetic diversity over broad areas, human impacts, primarily by harvest and fire suppression, 

may have modified their fitness for future environments 

and human uses (Ledig 1992). 

Many other plants of ponderosa pine forests are either 

fire resistant or fire dependent. For example, since most 

fires begin near the end of a warm season drought, understory species whose seeds have long dormancy and 

whose germination is stimulated by high soil temperatures (Arctostaphylos pungens and Ceanothus fendleri ), are 

unaffected or benefitted by fire. Another fire adaptation 

is rapid sprouting after fire. Examples include oaks 

(Quercus spp.), alligator juniper (Juniperus deppeana), aspen, maples (Acer spp.), Scouler willow (Salix scouleriana), 

and serviceberry (Amelanchier alnifolia). 

The length of fire-free intervals is an important attribute 

of an area's fire regime. Long fire-free periods allow trees 

to grow adequately thick bark to protect the cambial cells 

of the lower stem and root crown from the lethal temperatures of the next surface fire. But during a long interval between fires, woody fuels and mistletoe brooms 

(dense, woody structures that develop in tree crowns parasitized by dwarf mistletoe) accumulate, increasing the 

probability that the crown will be scorched and/or the 

roots killed (Harrington and Sackett 1992). To prevent 

destructive, high-intensity fires, tree thinning and manual 

fuel removal (especially around the base of large trees) is 

performed as part of fuel-reduction burn prescriptions 

(Kurmes 1989; Brown et al. 1994; Covington and Moore 

1992; Harrington and Sackett 1992). 

Much current research is dedicated to estimating fire 

frequencies in the xerophytic and mesophytic ponderosa 

pine forests of the Southwest (Swetnam and Baisan 1996). 

Working in a ponderosa pine/Arizona white oak stand 

surrounded by chaparral in Arizona, Dieterich and 

Hibbert (1990) reported that low-intensity, surface fires 

occurred somewhere within the 87 hectare (ha) study site 

in 67 of the years between 1770 and 1870. In similar open 

pine forests of the Rincon Mountains, Baisan and Swetnam 

(1990) reported a mean fire interval (MFI) of 7 years in the 

century before 1890; these were low-intensity, surface fires. 

In the earliest study of a mixed conifer forest containing 

ponderosa pine, Dieterich (1983) reported a 22-year MFI 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 

1910 1930 1950 1970 1990 1995 

' " 

~~-& 

rO 

A 

k; A 

& 
Chapter 1 

(combining fires in several forest communities) in the 

Thomas Creek drainages in Arizona before 1890. The lack 

of fire since then allowed shade tolerant trees, such as 

white fir and Engelmann spruce, to establish and increase 

overall tree density in the study area. 

There is evidence that ponderosa pine forests with 

grassy understories in the xerophytic or mesophytic zones 

have similar fire regimes. Unpublished data from the Sacramento and White Mountains, New Mexico (Huckaby 

and Brown 1996) reveal high fire frequencies in Douglasfir and white fir forests where grasses were a major component of the forest understory. Between 1712 and 1876, a 

Douglas-fir climax site on James Ridge had 25 fires (MFI 

= 7 years). Between 1790 and 1890, the MFI was 4.5 years 

for a white fir climax site (white fir/Arizona fescue association) on Buck Mountain. Fires at each of these sites were 

low-intensity, surface fires that maintained an open forest structure. High fire frequencies (low MFIs) were also 

found in a wide variety of other ponderosa pine and mixed 

conifer forest types, with or without present-day grassy 

understories. 

Data indicating frequent ground fires before the 20th 

century have been collected for the Pinaleno Mountains, 

Arizona (Grissino-Meyer et al. 1995), the Jemez Mountains, New Mexico (Allen et a1 1995; Touchan et al. 1996), 

the Mogollon Mountains, New Mexico (Abolt et al. 1995), 

and the Sandia and Manzano Mountains, New Mexico 

(Baisan and Swetnam 1995b). In all cases, the MFI before 

1890 was 12 years or less. Savage and Swetnam (1990), 

Abolt et al. (1995), and Touchan et al. (1995) suggest that 

continuity of understory fuels, especially the grass layer, 

maintained high frequencies of low-intensity, surface fires 

along the entire gradient from woodlands to the sprucefir forests. This hypothesis is supported by evidence that 

forests with grassy understories were once extensive and 

continuous over a large elevational range. Descriptions 

of forests around the turn of the century noted open, large 

areas not confined to xerophytic pine forests. Most ecologists agree that hot, crown fires were not extensive in these 

open ponderosa pine forests, although small thickets 

would have been destroyed by spot crown fires. Because 

fires have been suppressed in the last 100 years, much of 

the area classified as ponderosa pine cover type was previously within the mesophytic mixed conifer climate 

(Beschta 1976; Johnson 1994; Covington and Moore 1994). 

Other Natural Disturbances 

Although only a few species of forest insects and pathogens described are the principal natural agents of change 

in Southwestern ponderosa pine forests, they interact with 

each other and with other abiotic factors to generate forests with varying species composition and landscape patterns (Lundquist 1995a). Some of these organisms have 

coevolved with host trees, while others, such as white pine 

blister rust, were recently introduced (Wilson and Tkacz 

1996). Each insect or pathogen attacks only certain host 

species and parts (foliage, stems, roots) and is controlled 

by various host and environmental conditions. Tree competition, drought, lightning strike, wind damage, site conditions, and fire can stress a tree and increase its vulnerability to &pportunistic insects and fungi. The initial attack 

can lead to invasion by other insects and pathogens, tree 

death, and deterioration. Many insect and pathogen species do not require the host tree to be stressed before attack, instead they proceed rapidly as host resistance is 

overcome (Franklin et al. 1987). Injury from biotic agents 

can also increase damage from abiotic factors. For example, decay increases the likelihood of stem failure, and 

mistletoe brooms provide fuel continuity from the ground 

to the crown. 

In addition to fire, important abiotic factors affecting 

ponderosa pine in the Southwest are drought, lightning, 

winter drying, and hail (Rogers and Hessburg 1985). 

Droughts several years long occur periodically across the 

region and are frequently severe. Pine mortality is usually associated with secondary bark beetles at the end of 

the drought (Lightle 1967). Lightning is a common cause 

of mortality for large ponderosa pine, especially in certain geographic areas with high lightning frequency such 

as the Mogollon Rim, Arizona (Pearson 1950). Winter drying is the result of foliage desiccation when soil and roots 

are frozen (Schmid et al. 1991). The affect on ponderosa 

pine can be devestating but most trees recover, as in 1985 

in northern New Mexico (Owen 1986). Violent summer 

thunderstorms can produce severe hail, stripping trees of 

much of their foliage. Such a storm occurred on the 

Mescalero Apache Indian Reservation in the 1950s (Shaw 

et al. 1994). 

Insects 

Although many insect species feed on nearly every part 

of ponderosa pine (Furness and Carolin 1977)) ecologically the most severe are the defoliators and bark beetles. 

Conifer sawflies (Diprionidae) and various moths, especially the pandora moth (Coloradia pandora), occasionally 

reach outbreak status; however, although foliage is removed, trees usually recover. In the mesophytic ponderosa pine zone, the western spruce budworm (Choristoneura occidentalis) can induce a temporary increase in 

ponderosa pine growth while depressing the growth of 

competing Douglas-fir and white fir, which are the principal budworm hosts (Swetnam and Lynch 1993). Pine 

bark beetles (Dendroctonus and Ips) feed on the cortex and 

cambium and introduce fungi that promote rapid tree 

death and decay. 

10 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Ecology of Southwestern Ponderosa Pine Forests 

The roundheaded pine beetle (D. adjunctus) is the most 

common bark beetle that attacks pines in the Southwest 

(Chansler 1967; Furness and Carolin 1977). This beetle 

infests ponderosa and related pines from Colorado and 

Utah south to Guatemala (Massey et al. 1977). Outbreaks 

have occurred periodically and killed large numbers of 

pole-and sawtimber-sized ponderosa pine (trees larger 

than 23 cm dbh), especially in the White and Sacramento 

Mountains in 1950, 1960s, 1970s, and 1990s (Lucht et al. 

1974; Chansler 1967; Flake et al. 1972). Eruptions of 

roundheaded pine beetle are often accompanied by the 

western pine beetle, Mexican pine beetle, and Ips beetles, 

which establish on poor sites or in mistletoe infested areas. Trees are attacked in groups of 3 to over 100; smaller 

trees and those in dense thickets are most likely to be attacked. Killed trees rapidly develop a brown cubical decay and break near the groundline. 

The western pine beetle (D. brevicomis) is most damaging in the far western United States and British Columbia, but its range extends into the Southwest and Mexico 

(DeMars and Roettgering 1982). This beetle usually occurs in one or a few widely scattered trees already weakened by drought, lightning, stagnation, root disease, or 

other disturbances. Although it usually creates small 

canopy gaps, the western pine beetle can cause significant mortality and increased fire hazard in drought and 

competition-stressed stands; an outbreak occurred near 

Flagstaff, Arizona from 1980 to 1982 (Telfer 1982). 

The mountain pine beetle (D, ponderosae) is the most extensive bark beetle to attack ponderosa pine in western North 

America. In the Southwest, however, outbreaks have been 

restricted to the north Kaibab Plateau (Parker 1980). Like the 

roundheaded pine beetle, the mountain pine beetle can develop large populations in dense stands and then disperse 

to kill large numbers of otherwise vigorous trees. 

The Arizona five-spined engraver beetle (Ips lecontei) is 

the most common bark beetle in central and southern 

Arizona. Although this beetle usually occurs in slash and 

small, weakened trees, it has multiple generations per year 

that allow populations to build quickly (Parker 1991). 

Dwarf Mistletoe 

Southwestern dwarf mistletoe (Arceuthobiurn vaginatum 

subsp. cryptopodum) is a widely distributed parasitic plant 

that causes severe damage and mortality to its principal 

host, ponderosa pine (Hawksworth and Wiens 1995). 

Southwestern dwarf mistletoe occurs throughout the 

range of ponderosa pine in New Mexico and Arizona and 

extends into neighboring states. Other infected pines include Arizona pine, Apache pine (Pinus engelmannii), and 

Colorado bristlecone pine (P. aristata). Region-wide, 40 

percent of the commercial pine forest is infested. Infection is more common in some forests; 70 percent of the 

stands in the Lincoln National Forest are infested (Maffei 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 

and Beatty 1988). Growth loss and mortality from this 

mistletoe in the Southwest is estimated at 150 to 200 million board feet per year (Walters 1978). The severity of 

growth loss for infected trees is related to disease intensity (Hawksworth 1977). Radial growth increment is reduced by 9 percent, 23 percent, or 53 percent for trees 

moderately infected (class 4), heavily infected (class 5), or 

very heavily infected (class 6), respectively (Hawksworth 

1961). Survival of infected trees is also reduced; 10-year 

modality rates of 9 percent, 12 percent, and 38 percent for 

trees rated class 4, 5, and 6, respectively, have been observed (Hawksworth and Lusher 1956). Other effects of 

mistletoe infestation include reduced reproductive output (Koristan and Long 1922) and increased likelihood of 

attack and mortality from bark beetles and pandora moth. 

In mesophytic forests, selective loss of ponderosa pine 

from dwarf mistletoe can accelerate conversion to Douglas-fir or white fir. However, Douglas-fir in ponderosa 

pine stands is a principal host for the Douglas-fir dwarf 

mistletoe (Arceuthobium douglasii), which is very damaging to that species. The dense swollen and branching structures resulting from mistletoe infection, known as witches' 

brooms, often form near the ground. Broomed trees are 

more readily killed by even a low-intensity fire, and these 

brooms provide a fuel ladder into the crown (Alexander 

and Hawksworth 1974; Harrington and Hawksworth 

1990). Mistletoe spread and intensification is greatest in 

stands with a multiple story structure. 

Although there is evidence that mistletoe abundance 

has increased in the last century (Maffei and Beatty 1988), 

it has long been an important natural disturbance (figure 

5). In addition to mistletoe shoots and associated insects 

providing wildlife forage, infections and brooms are especially suitable for roosting and nesting birds. Dead tops 

and snags created by mistletoe also enhance wildlife habitat (Bennetts et al. 1996; Hall et al. this volume; Rich and 

Mehlhop this volume). Although mistletoe infestation can 

increase canopy and wildlife diversity (Mathiasen 1996), 

the desired amounts or tolerable levels for resource objectives other than timber production are unknown. 

Plant Pathogens 

Root disease fungi, including Arrnillaria ostoyae and 

Heterbasidion annosum, are a major cause of tree mortality 

and growth loss in the Western United States. In the Southwest, 446 thousand ha are seriously affected by root diseases (DeNitto 1985), which reduce growth by 10 percent 

region-wide or by 25 percent in severely damaged stands 

(Rogers and Hessburg 1985). Complexes of root disease 

with insects and pathogens were associated with 34 percent of the mortality in all stands (Wood 1983). Root disease is more common in the mesophytic than xerophytic 

ponderosa pine zone. Armillaria is generally found in 

stands 10 to 25 years old, but in the Jemez Mountains, 
Chapter I 

New Mexico, 50 years of selective logging intensified dis- high canopy densities and increase patchiness. As discussed 

ease severity and lead to extensive mortality in all ages of in the wildlife section of this chapter, these changes to forest 

ponderosa pine (Marsden et al. 1993). Annosus root disease structure are important to wildlife. Many of the organisms 

also infects ponderosa pine throughout the Southwest but is described here contribute to gap dynamics, forest structural 

less common than other diseases. Like the mortality patches diversity, and wildlife use in ponderosa pine forests 

caused by dwarf mistletoe, centers of root disease reduce (Lundquist 1995a, 199%). 

Figure 5. Stand of ponderosa pine June 4, 1990, Tonto Basin, Arizona. The multistory structure and high incidence of dwarf mistletoe 

disturbance is evidenced by the many large brooms in lower crowns and progressive dieback of upper crowns. Giffort 

Pinchot, the photographer, noted the sparsity of understory vegetation, consisting of only a little lupine. 

12 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Ecology of Southwestern Ponderosa Pine Forests 

The white pine blister rust caused by the fungus 

Cronartium ribicola, was discovered in the Sacramento 

Mountains of New Mexico in 1990. This fungus infects 

Southwestern white pine but has an indirect impact on 

ponderosa pine because as these tree species compete in 

mixed conifer forests, southwestern white pine is less susceptible to insects and diseases than ponderosa pine. Rust 

mortality of Southwestern white pine could possibly decrease its buffering affect on various other disturbances 

and will have a major impact as the disease progresses 

(Wilson and Tkacz 1996); at present the ecological consequences are speculation. 

Wood Decay Fungi 

Although there are many wood decay fungi (Basidiomycetes) of ponderosa pine (Gilbertson 1974), a few species commonly cause trunk rot. Red rot (Dichomitus 

squalens) is a major stem decay fungus of live ponderosa 

pine in the Southwest (Andrews 1955). An estimated 15 

to 25 percent of the gross volume in old-growth ponderosa pine was decayed by red rot (Andrews 1955; Lightle 

and Andrews 1968). Common decay fungi that cause 

brown cubical rots of ponderosa pine include Phellinus 

pini (red ring rot), Fomitopsis oficialis, Phaeolus schweinitzii 

(more common on Douglas-fir), Veluticeps berkeleyi, and 

Lentinus lepideus (usually associated with fire scars). In 

addition to their important roles in nutrient recycling and 

organic decomposition, decay fungi provide the soft wood 

habitat in snags that is required by numerous cavity-dependent species as discussed in later chapters. 

Overstory-Understory 

Relationships 

General 

Rather than directly affecting passerine birds, land managers manipulate forest composition and structure. To 

understand why and how the environment of passerine 

birds in ponderosa pine forests is always changing, it is 

necessary to comprehend the interactions that determine 

forest composition and structure. Plant succession in ponderosa pine forests is a complex of overstory-understory 

(0-U) dynamics responding to disturbances. Overstoryunderstory refers to the effects of tree canopies (overstory) 

and ground-layer plants (understory) including shrubs, 

herbaceous vegetation, cryptogams (mostly mosses and 

lichens) on the soil surface, and tree seedlings. The heights 

that species display canopies is a continuum, so there is 

no precise definition the 0 and U classes. Trees, shrubs, 

herbs, and nonvascular plants (such as mosses and lichens) 

are usually easily distinguished, and their canopy levels 

can be assigned to local condition classes. Competition 

also occurs in the soil; for example, as root competition 

for soil water or the mycorrhizal differences between herbaceous and coniferous vegetation (Kendrik 1992; 

Klopatek 1995). Figure 6a, a generalized model, shows 0 

and \U competing, but their affects cannot be separated 

from other abiotic and biotic factors such as prescribed or 

wild fires, forest insects and pathogens, and soil microorganisms. At any location, both climate and soil influence 

the reactions shown in figure 6b. This climate, soil, vegetation influence is the basis of ecosystem classification, 

mapping, and interpretation used by the USDA Forest 

Service Southwest Region (USFS 1991). Plant succession, 

which after a fire holocaust killed virtually all of the aboveground vegetation, has been studied quantitatively, most 

notably after the La Mesa fire near Los Alamos, New 

Mexico (Foxx 1996) 

A large class of 0-U relationships are associated with 

tree death and falls (Denslow and Spies 1990). Canopy 

gaps operate on individual trees, especially the larger 

dominant or codominant trees. In open, low density pine 

forests before European settlement, gap processes may 

have been unimportant because recurrent fires determined 

tree and understory spatial patterns. However, in this century as tree densities greatly increased, new spatial patterns were created by expanding root rot pockets (Wood 

1983) and other diseases, increased abundance of dwarf 

mistletoe, insect outbreaks, and rapid filling of former 

open areas by tree regeneration (Allen 1989). Today, especially in xerophytic forests, canopy gap processes may be 

dominant in 0-U dynamics (Lundquist 1995b, 1995~). 

In mesophytic pine forests, the death of large trees may 

be important to maintain shade intolerant trees such as 

ponderosa pine, aspen, and gambel oak. Forest pattern is 

determined by combinations of patchy, natural fires (Jones 

1974) and other gap-creating factors that stress trees and 

expose them to numerous mortality agents (Franklin et 

al. 1987; Lundquist 1995~). In both xerophytic and mesophytic pine forests, silvicultural (Schubert 1974; Oliver and 

Ryker 1990) or disturbance management (Geils et al. 1995) 

are used to create or maintain gaps in the absence of fire. 

In mesophytic forests, however, small canopy gaps are 

usually filled by shade tolerant trees (Dieterich 1983; 

Ffolliott and Gottfried 1991). Small gaps do not ensure 

that shade intolerant trees, such as ponderosa pine, gambel 

oak, or aspen, or herbs, will be maintained (Moir 1966). 

Understory Influence on Trees 

Research has focused on competition between the herbaceous layer, particularly grasses and tree seedlings 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
  

Chapter 1 

ABIOTIC 

CLIMATE \ 

Vertebrates 

lnvertebrates 

Soil organisms 

Wood rot fungi 

Forest Succession 

(exte 

ABIOTIC / \\ BIOTIC 

(external factor) (external factor) 

Climate Vertebrates 

Geology Invertebrates 

Fire 

Topography 

Etc. 

h / 

Forest stand 

(internal factor) (internal factor) 

other invatebrates 

I I 

Figure 6, a) Simplified, schematic representation of overstory-understory relationships and ecological associations (Verner et al. 

1992). b) A forest stand (internal factors) and the surrounding environment (external factors) that influence the nature and 

intensity of stand dynamics. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Ecology of Southwestern Ponderosa Pine Forests 

(figure 6a). Competition can be for light (Moir 1966), nutrients (Elliott and White 1987; Moir 1966), water (Larson 

and Schubert 1969; Embry 1971; Miller 1988), and combinations of these (Moir 1966). Sometimes, shrubs can lessen 

tree seedling survival or diameter growth (White 1987; 

Rejmanek and Messina 1989). In the Southwest, Festuca 

arizonica is particularly competitive because it consumes 

soil moisture during the drought season of April and May 

(Pearson 1931,1942,1950). Allelopathy (compounds produced by one plant species that inhibit the establishment 

or growth of another species) has also been suggested as a 

means of tree control (Rietveld 1975; Stewart 1965); however, this subject has received little recent attention. The detrimental effects of understory vegetation on tree establishment can be mitigated by grazing and burrowing animals. 

Browsing, grazing, or burrowing animals create microsites 

where reduced herb or shrub competition and exposed mineral seedbeds enhance pine seed germination, seedling survival, and growth (Rummell1951; Doescher 1987). 

Fire also has direct affects on small trees and ground 

cover (figure 6a). Generally, fire stimulates the understory 

while killing tree seedlings, saplings, or entire thickets. 

Fire is the principal means of restoring cover and grass 

vigor and maintaining or invigorating shrubs (Martin 

1983; Harper and Buchanan 1983; Biswell1972; Bunting 

et al. 1985; Pearson et al. 1972; Harris and Covington 1983; 

Andariese and Covington 1986; Ffolliott et al. 1977; Moir 

1966). Fire favors understory vegetation by reducing tree 

competition for sunlight, moisture, and nutrients, accelerates the nutrient cycle, and, by killing trees, changes the 

soil-water relationship usually to the benefit of ground 

vegetation. In the past, fire was often carried by extensive 

and continuous understory vegetation, resulting in smalltree mortality over large areas (Abolt et al. 1995). Before 

European settlement, recurrent fire was the principal agent 

maintaining the relationship between overstory trees and 

understory vegetation. When the herbaceous or herbshrub vegetation became depleted by overgrazing 

(Touchan et al. 1995; Savage and Swetnam 1990), heavy 

tree seedling occurred in the Southwest and elsewhere. 

The effects of grazing are discussed in Chapters 2,3 and 

6. Fuel reduction and reduced competition between trees 

and the understory have resulted in increasing tree densities during this century (Pearson 1950; Allen 1989; Savage and Swetnam 1990; Brown et al. 1994; Touchan et al. 

1996; Moir and Fletcher 1996). 

Tree Influence on Understory 

Once past their seedling stage, continued growth of 

pines or other trees reduces cover, vigor, density, and biomass of many understory species. Particularly affected are 

species that grow best in open meadows or full sunlight 

(Ffolliott and Clary 1982). However, O-U dynamics vary 

greatly among sites and forest types, so generalized statistical models are unsatisfactory (Mitchell and Bartling 

1991). Gap processes may be important, depending on fire 

history, gap size, and gap microclimate. Dense thickets of 

conifers in their sapling or pole stages of succession can 

extinguish understory vegetation. In livestock grazing 

allotments, the adverse influence of trees on ground vegetation is well-known in ponderosa pine/bunchgrass and 

ponderosa pine/blue grama rangelands (Arnold 1950; 

Reid 1965; Clary and Ffolliott 1966; Currie 1975; Johnson 

1953; Smith 1967; Brown et al. 1974). Biswe11(1972), citing 

data from research in the Black Hills, reported declines in 

herbage biomass from 1,860 kg/ha in openings to 39 kg/ 

ha under closed ponderosa pine canopies. In northern 

Arizona pine/bunchgrass ranges, Jameson (1967), using 

negative exponential equations to fit tree basal areas to 

herbage harvest data, showed declines from 784 kg/ha in 

areas without trees to less than 56 kg/ha where pine basal 

areas exceeded 23 m2/ha. Working in ponderosa pine 

stands with a grassy understory in eastern Washington, 

Moir (1966) reported that low supplies of nitrogen and 

reduced light acted additively and interactively under 

developing pine thickets to suppress Festuca idahoensis. 

Moir found reduced inflorescence production in stressed 

grasses followed by reduced foliar cover. 

Oaks are a valuable resource used by numerous birds 

and mammals. The adverse relationships between pines 

and oaks can be severe. Neither deciduous nor evergreen 

oaks tolerate shade. They grow best in full sunlight and 

are often quickly started by hot, stand-replacing fires that 

induce sprouting. Sprouts grow rapidly, soon dominate 

burned sites, and often suppress pine regeneration and 

growth (Hanks and Dick-Peddie 1974; Harper et al. 1985). 

However, oaks are suppressed and die back once conifers 

overtop them. In open stands where oaks and junipers 

form a distinctive mid-layer canopy, such as the pine-oak 

woodlands of Marshall 1957 and ponderosa pine/gambel 

oak forests, oaks persist as mid-level trees or as groups of 

clustered stems if the density or basal area of taller, emergent pines is low. But as pine canopies close during advanced stages of forest succession, oaks die back and are 

maintained as suckers from below-ground rootstock. 

Suckering can take place for decades until the next crown 

fire occurs (USFS 1986, 1987a, 198%). Oaks growing in 

full sunlight will coppice from basal portions of the stem 

and grow rapidly if fire or cutting kills the overstory trees. 

Both coppicing and suckering are adaptations to fire. If 

large oak trees, those greater than a specified diameter 

and taller than a specified height, are part of the desired 

landscape, then overtopping by conifers must be prevented until the desired heights and diameters of oak are 

attained. Before about 1890, recurrent surface fires helped 

maintain oak and pine codominance (Dieterich and 

Hibbert 1990; Moir 1982; Swetnam et al. 1992). Marshall 

(1963) claimed that the grassy pine-oak savannas in northern Mexico were maintained by natural fires, whereas 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 1 

comparable, densely stocked and grass deficient pine-oak 

forests in the United States were due to aggressive fire 

suppression programs. 

Plant-Animal Relationships 

Overstory-understory relationships are directly and 

indirectly linked by numerous food webs. Some of the 

more well-known relationships are mentioned in this 

chapter. Nearly all ponderosa pine forests in the Southwest contain livestock grazing allotments (Raish et al. this 

volume; Finch et al. this volume) and many areas contain 

elk and deer. Mitchell and Freeman (1993) discuss the complex interactions of fire, deer, livestock, predators (especially mountain lions), and understory vegetation on the 

North Kaibab Plateau, which contains extensive ponderosa pine forests (Madany and West 1983). Herbivores 

directly affect tree structures by trampling or browsing 

on tree seedlings and saplings (Cassidy 1937; Currie et al. 

1978; Eissenstat et al. 1982; Pearson 1950; Crouch 1979). 

Browsing on small trees may affect both conifers and 

deciduous trees. Aspen regeneration is a preferred food 

by domestic livestock, elk, and deer; severe browsing prevents regeneration where small aspen patches are part of 

a larger landscape (Crouch 1986). By contrast, aspen regenerates well in mesophytic forests after extensive standreplacing fires as, for example, the Escudilla Mountain 

burn in Arizona. Browsing can also affect other important understory species such as gambel oak (Quercus 

gambelii), antelope bitterbrush (Purskia tridentata), junipers, 

snowberry (Sympkoricarpos spp.), and deerbrush (Ceanothus fendleri) (Harper et al. 1985; Harper and Buchanan 

1983; Kruse 1992). 

Bark damage by bears, porcupines (whose principal 

food in winter includes pine phloem), antlered animals, 

and humans affects individual trees. Feeding impacts on 

selected ponderosa pines by porcupines and Abert's squirrels may have substantial affect on tree genetics ( Linhart 

et al. 1989). The Abert's squirrel was described by Pearson 

(1950) as "one of the most destructive of all animals" because of twig cutting, seed and cone herbivory, and defoliation of terminal twigs of ponderosa pine. As mentioned, 

animals feeding on understory shrubs and herbs increase 

tree densities and dominance by reducing understory 

competition. Doescher (1987) and others suggested livestock grazing practices that create a favorable balance 

between livestock numbers and season of grazing, forest 

or plantation pine growth, and maintenance of understory 

productivity. 

Animals have an important role through mycophagy 

(fungus eating) in forest regeneration and tree growth. 

Hypogeous fungi (fruiting below ground) are a major 

source food of small rodents, deer, and javelinas (Kotter 

and Farentinos 1984a, 1984b; Hunt and Z. Maser 1985; 

Fogel and Trappe 1978). Nitrogen fixing bacteria and germinating spores of mycorrhizal fungi in the fecal pellets 

of these animals can enhance pine seedling survival and 

growth. Given the important but complex roles of mycorrhizal fungi, trees, and understory vegetation (Brundrett 

1993; Klopatek 1995; States 1985), animals that disperse 

fungal spores, including small mammals, grasshoppers, 

worms, ants, wasps, and some birds, play an indirect but 

significant role in 0-U relationships. 

As t~ee strata develop they modify the composition, 

cover, and density of understory shrubs and herbs. As the 

understory changes, so does the composition of prey species dependent on it. Examples are the predator-prey relationships of the Mexican spotted owl and northern goshawk during various stages of forest succession (figure 

6b). Both of these raptors are found in ponderosa pine 

forests of the Southwest. Their persistence may involve 

treatment of tree structure and density to ensure that understory shrubs and herbs have cover characteristic~ 

needed by prey populations (Ward and Block 1995; 

Reynolds et al. 1992, 1996). The complexity of these ecological interactions (figure 6b) was described for the California spotted owl by Verner et al. in 1992 but also applies 

to the Mexican spotted owl in the Southwest. 

Hidden Diversity Organisms 

Hidden diversity organisms (soil and litter invertebrates, plant pollinators, cone and seed predators, wood 

decay organisms, vertebrate parasites, mycorrhizal fungi, 

and other seldom studied organisms) are important in 

nutrient cycling and plant-water relationships in ponderosa pine forests (Castellano 1994; Mason 1995; Gilbertson 

1974; Maser and Trappe 1984; States 1985). Some of these 

organisms are related to decay processes in litter and 

coarse woody debris. However, their role in ecosystem 

dynamics of litter and coarse woody debris has changed 

from what it was before European settlement. Recurrent 

ground fires in pine forests before about 1890 kept pinederived fuels to a minimum. Ponderosa pine snags may 

have persisted for a time, but downed fuels were mostly 

burned off by frequent surface fires. Early settlers described grassy pine savannas, not woody ground debris, 

although some old photos do show some logs (Woolsey 

1911; figure 5). Wood decay organisms and their associated food webs were present in pre-1900 forests, but their 

abundance and their roles in fire-adapted forests is unknown. The stand replacing fire holocausts experienced 

in the past 10 years burned the aboveground vegetation 

and destroyed mycorrhizae in scorched soils (Klopatek 

1995; Klopatek and Klopatek 1993; Vilarino and Arines 

1991). However, plant succession after these stand replacing fires has hardly been studied (see Foxx 1996). 

There is concern that diversity in forest ecosystems is 

decreasing. Wilson (1992) discusses this situation for tropical forests, and it is also relevant to ponderosa pine forUSDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Ecology of Southwestern Ponderosa Pine Forests 

ests. Among functions, such as in carbon and nutrient 

cycles, hidden diversity organisms possibly contribute to 

ecosystem resilience, which is the ability of ecosystems to 

recover or adjust to disturbances. Management should 

maintain hidden and other kinds of diversity of native 

organisms to restore or sustain pine ecosystems (Kauffman 

et al. 1994; Opler 1995; Maser and Trappe 1984; Reynolds 

et al. 1992; Rapport and Yazenko 1996 ). 

Wildlife 

Ponderosa forests provide habitat for birds, mammals, 

reptiles, and amphibians including threatened or endangered species, neotropical migratory birds, and game species. Detailed information about ponderosa pine forest 

habitat use by passerine birds is in Chapters 3 and 6. The 

following section reviews the importance and use of successional stages in ponderosa pine forests by vertebrates. 

Overstory Tree Influence on Wildlife 

The overstory structure and plant diversity of ponderosa 

pine forests affect their use by wildlife. Important forest features include age, size class, and of canopy cover trees, patch 

size of tree groups, multiple or single canopy layers, and 

presence of other vegetation such as gambel oak and juniper. Review of the literature and analysis of R3HARE, which 

is a computerized wildlife relational database for Southwestem forests (Patton 1995), document wildlife use patterns of 

these ponderosa pine forest structures (Benoit 1996). The following descriptions of forest structural stages mention a few 

of the vertebrates associated with the stages. 

Structural Stages 

Six vegetative structural stages, VSSl to VSS6 (Thomas 

1979; Moir and Dieterich 1988), occur within ponderosa 

pine forests through timber harvest, wild or prescribed 

fires, diseases, insects, or windfall, which all affect the 

dynamics of overstory and understory of forest succession. The VSS stages apply to forest stands during succession or stand development; each stage is important to different species of wildlife for feeding, cover, or reproduction. 

Canopy cover classes of trees (A=O to 40 percent, B=40 to 

60 percent, C=60 percent and over) within each stage also 

influence how the area is used. Cover includes thermal, 

hiding, and reproductive cover. Many habitat generalists, 

such as bear, turkey, elk, mule deer, bobcat, coyote, and 

northern goshawks, use all structural stages. 

Openings (VSS1) occur after significant disturbance, 

such as fire or timber harvest (Hoover and Wills 1984), or 

gap processes (Lundquist 1995b). Openings may be maintained as meadows or parks in pine savannas where recurrent surface fires occur and may include a snag stage 

after a stand replacing fire (Moir and Dieterich 1988). Deer 

and elk rely heavily on openings for forage (Hoover and 

Wills 1984). Openings provide primary habitat for numerous other vertebrates that use grasses for shelter or feed 

on grasses, seeds, or insects. 

Seedlings and saplings (VSS2, trees d2.7 cm dbh) provide some hiding cover but may have little forage value 

depending on tree density (Hoover and Wills 1984). Small 

tree seedlings of low density often grow in an herbaceous 

or shrubby environment, which can provide some forage 

and cover and are used primarily by habitat generalists, 

some of the VSSl species, and shrub nesting birds. As seedlings grow to saplings the tree canopies close and forage 

declines. 

Young stands (VSS3, trees 12.7 to 30.2 cm dbh) are usually dense and clumped in unmanaged stands. Tree 

canopy cover often exceeds 70 percent. Stands have sparse 

herbaceous understory, few snags, and single-storied 

structure (Hoover and Wills 1984). Denser stands provide 

thermal cover for habitat generalists and some raptors, 

but their value for forage and hiding cover is mi;imal. 

With sparse understories there is little use by other vertebrates, except possibly animals feeding on fungi. 

Mid-aged stands (VSS4, trees 30.5 to 45.5 cm dbh) begin cone production, tend to be multi-storied, and provide small snags suitable for some cavity nesters (Hoover 

and Wills 1984). Species other than generalists in this stage 

include squirrels, pygmy nuthatches, and various raptors. 

Mature stands (VSS5, trees< 45.5 cm dbh) may be single 

or multi-storied, with more litter and dead and downed 

debris in stands without fire for a long period. Mature 

stands may contain larger snags than in the VSS4 stage. 

These stands provide a good seed crop and are used for 

thermal cover by big game (Hoover and Wills 1984). Species found in the VSS~ stage also use mature stands, In 

addition, mature stands have high value for feeding and/ 

or cover for flickers and some owls, hawks, eagles and 

passerine birds. 

Old growth forests (VSS6) provide single and multiple 

stories with many mature trees and dense canopies (>40 

percent) in stands not experiencing ground fires in their 

VSSl and VSS2 stages. Old, yellow-pine forests, which 

were extensive before European settlement, are open and 

relatively devoid of coarse woody debris. In ponderosa 

pine/ bunchgrass environments before about 1890 in Arizona and New Mexico, ponderosa pine required at least 

300 years beyond the herbaceous or burned snag stages 

to develop old growth characteristics (Moir and Dieterich 

1988). Today old growth stands are heavily stocked, have 

much dead and downed material and numerous large 

snags, and contain trees that are >61 cm dbh (Moir 1992). 

Without restoration, most of these decaying, old growth 

stands are at risk of fire holocaust similar to the La Mesa 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 17 
Chapter 1 

and other large burns in the last few decades (figure 4; 

Allen 1996; Moir and Dieterich 1988). Large trees and 

snags provide the best source of carities for vertebrates. 

The primary users of this stage are passerine birds (Hall 

et al. this volume; Rich and Mehlhop this volume) and 

raptors. 

Understory Tree Influence on Wildlife 

All plants contribute to the ecology of ponderosa pine 

forests and influence the number of vertebrates and invertebrates. Gambel oak (Quercus gambelii) and alligator 

juniper (Juniperus deppeana) are often associated with ponderosa pine and provide additional structural diversity, 

food, thermal and hiding cover, and nest sites for numerous species. The numbers of species below are from 

R3HARE (Patton 1995) and Nagiller et al. (1991). 

Gambel oak provides a key habitat component for birds 

in pine-oak forests and offers valuable alternate cavity 

nesting sites when pine snags are limited (Rosenstock 

1996). All stages of oak, but especially large trees, are important to wildlife (Kruse 1992). Mature trees benefit the 

most species with regard to food and nesting sites. 

Shrubby oaks result from suckering and coppicing, as discussed above. The sprouts and trunks provide food, hiding and thermal cover for deer, elk, and numerous birds 

(Nagiller et al. 1991). Areas of brush and sprouts may provide important fawning grounds for deer, and cover and 

foraging habitat for rabbits and rodents (Kruse 1992). 

Taller clonal oak groups provide habitat for foliage nesting birds (Szaro and Balda 1979). Foliage and buds provide food for deer, elk, and birds (mourning dove, bandtailed pigeon, turkey, rufous-crowned and chipping 

sparrows, and spotted towhee). Arthropods living in the 

foliage and on twigs provide food for birds such as the 

screech owl, pygmy and white-breasted nuthatches, and 

brown creeper (Patton 1995). 

Some clonal oak and mature trees produce acorns that 

feed 21 species of mammals and 20 species of birds such 

as corvids and woodpeckers (Patton 1995). Acorns are the 

preferred food of Abert squirrels, band-tailed pigeons, 

turkeys, deer, elk, and acorn woodpeckers. Acorn crops 

may influence the numbers of these species. Large trunks 

provide hiding and thermal cover for deer, elk, rabbits, 

and birds (Nagiller et al. 1991). As the trees age and become less vigorous, acorn production drops, but hollow 

boles and limbs offer cavities sheltering 10 species of mammals and 19 species of birds such as bats, squirrels, 

racoons, owls, woodpeckers, and passerine birds (Nagiller 

et al. 1991). 

Young alligator junipers provide hiding cover for elk, 

deer, rabbits, turkey, small mammals, and birds (Nagiller 

et al. 1991). Large trees provide nesting cover for birds 

such as pinyon jays, scrub jays, and blue-gray gnatcatchers (Degraff et al. 1991); thermal cover for deer, elk, and 

small mammals (Abbott 1991); and juniper berries as food 

for several species of birds and small and large mammals. 

Alligator juniper provides food and cover for wildlife all 

year long and is critically important when deep snows 

make other food sources unavailable. 

Wildlife Communities 

Althoygh overstory and understory tree structure and 

diversity provide important habitat components for wildlife, no particular structure or species can satisfy the needs 

of the entire wildlife community. Wildlife community use 

of Southwestern ponderosa pine forests is illustrated using the R3HARE database (Patton 1995) and the Coconino 

National Forest. This forest has xerophytic and mesophytic 

ponderosa pine stands and numerous other habitats such 

as desert scrub, pinyon-juniper, riparian, mixed conifer, 

and grasslands (Benoit 1996). Of the 435 species that occur in the Coconino National Forest, 50 percent use ponderosa pine forests to meet some or all of their habitat 

needs. This includes 56 percent of the mammals, 46 percent of the birds, 61 percent of the reptiles, and 54 percent 

of the amphibians. Eighteen percent of Coconino species 

(mainly mammals, reptiles, and amphibians) use the ponderosa pine habitat year round. Thirteen percent use it in 

summer only, 2 percent in winter only, and 17 percent as 

fringe habitat or transient habitat. The majority of birds 

(75 percent) use it as fringe, transient or summer habitat 

(Benoit 1996). 

Overall vegetative structural stage use by wildlife 

(Patton 1995; Benoit 1996) is fairly evenly distributed with 

slightly higher use in mature and old growth forests and 

B (40 to 60 percent) and C (60 percent and over) canopies. 

Young stands and A (0 to 40 percent) canopies are used 

the least. The distribution is also somewhat uniform across 

all stages for species for which certain vegetative structural stages have high value. Use by threatened, endangered, sensitive, or dependent species (those that depend 

on certain structures in ponderosa pine for survival), and 

birds is also fairly uniform across all stages. Mammals 

follow an opposing pattern, with higher use occurring in 

openings, seedlings, and saplings than in mature or old 

growth areas. Forest indicator species occur predominately in mid-aged and mature stands, and do not indicate overall use patterns in the community or those of 

species of special concern. Information on structural stages 

use by amphibians and reptiles is limited, but they appear to prefer VSSl and 2 and probably respond primarily on the microsite level. 

Sixty-one percent of birds using ponderosa pine in the 

Coconino National Forest are passerines (Patton 1995; 

Benoit 1996). Use is primarily in summer (44 percent) or 

as fringe habitat (23 percent). Passerine use is highest in 

mature and especially old growth stands. Eight of the 12 

dependent species are passerine birds associated with old 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Ecology of Southwestern Ponderosa Pine Forests 

growth. Use by canopy density is evenly distributed with 

a slight preference for B canopies. 

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26 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Ecology of Southwestern Ponderosa Pine Forests 

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U.S. Department of Agriculture, Forest Service. 64 p. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 2 

Contemporary Human Use of Southwestern 

Ponderosa Pine Forests 

Carol Raish, Wang Yong, and John Marzluff 

Introduction 

The ponderosa pine forests of the Southwest provide 

land, resources, products, and recreational opportunities 

for both urban and rural communities of the region and 

the nation. These human uses and activities affect resident and migratory bird populations in both negative and 

positive ways. This brief review focuses on three major 

kinds of human use that have the greatest potential to affect bird populations of the area: 1) commercial and personal-use wood harvest; 2) livestock grazing; and 3) recreation (USDI Fish and Wildlife Service 1995). In addition, 

growing urbanization, which also has the potential to affect bird populations, is briefly reviewed. The geographic 

focus is the USDA Forest Service land within the Southwestern Region (Region 3), located in Arizona and New 

Mexico, with a special emphasis on New Mexico and some 

of the long-standing, traditional use patterns of the state. 

Since another portion of this overview presents a history 

of human use of the ponderosa pine forest, this review is 

concentrated upon present-day uses and issues. 

Commercial and Personal-Use 

Wood Harvest 

Southwestern ponderosa pine forests provide wood and 

wood products for both commercial and personal purposes. Large-scale and small-scale commercial activities 

include the harvest gf sawtimber, poles, posts, and 

fuelwood. Personal-use fuelwood and Christmas trees 

constitute the major noncommercial products. Data from 

Region 3 indicate that there were 58,733 wood and wood 

product sales of all types during fiscal year 1995. Timber 

of all types cut on Forest Service lands in Arizona and 

New Mexico during the same period had a value approaching $9 million.' 

All figures on timber and wood producf sales and volume throughout 

this chapter were obtained from the USDA Forest Service Southwestern Region 3, Regional Office, Albuquerque, New Mexico, with the 

help of Milo Larson, Marlin Johnson, and Paul Fink. 

Ponderosa Pine as a Timber Resource 

To understand the effect of the various human uses on 

the ponderosa pine forest, it is helpful to review background information concerning these lands and their timber resources. 

Forest land falls into two major categories-timberland 

or woodland-based on levels of tree stocking. Timberland is forest land on which tree species, such as industrial roundwood products like ponderosa pine and 

Douglas-fir, make up at least 10 percent of the stocking 

level. Woodland areas are other forest lands on which timber species are not present at the minimum stocking level. 

Woodland tree species, such as pinyon and juniper, are 

typically not used for roundwood products other than 

fence posts but are an important source of fuelwood and, 

in some cases, Christmas trees (Conner et al. 1990). 

In 1986, of the 61 million hectares (ha) in Arizona and 

New Mexico, about 17 million ha or 28 percent were forest lands (Conner et al. 1990; Van Hooser et al. 1993). Onefourth of the forest land is reserved or withdrawn from 

timber harvest through statutes or administrative designations. More than 3.5 million ha are designated as 

nonreserved, commercial timberland. The ponderosa pine 

forest is the most extensive nonreserved timberland, accounting for more than 2.5 million ha, or over 72 percent 

of the timberland available for harvesting roundwood 

products in the Southwest. Nearly two-thirds (64 percent) 

of the ponderosa pine timberland is administered by public agencies (figure 1). The National Forest Service, with 

over 1.56 million ha, manages the largest area of ponderosa pine forest in the Southwest. Other public agencies 

such as the Bureau of Land Management and various state, 

county, and municipal governments administer just over 

57,000 ha. Ponderosa pine timberland in private ownership equals over 914,000 ha. Owners vary from individuals 

to large corporations, including Indian tribes, farmers, and 

ranchers (Connor et al. 1990; Van Hooser et al. 1993). 

Silvicultural Systems 

Silviculture has been defined as: 1) the art of producing 

and tending a forest; 2) the application of the knowledge 

of silvics in forest culture; and 3) the theory and practices 

of controlling forest establishment, composition, and 

growth (Smith 1962). In essence, silvicultural practices can 

be used to mold the forest in desired directions, forms, or 

USDA Forest Service Gen.Tech. Rep. RM-GTR-292. 1997 
Contemporary Human Use of Southwestern Ponderosa Pine Forests 

Area by ownership 

(in thousand ha) 

National Forest . Other public Private and tribal 

Figure 1. Ownership and adminstration of ponderosa pine timberland in Arizona and New Mexico (data summarized 

from Conner et al. 1990; Van Hooser et al. 1993). 

conditions. Economical wood production is commonly the 

primary objective. 

A silvicultural system that includes harvest cutting, regeneration, and intermediate treatments manages a stand 

of trees for an entire rotation. Regeneration cuts usually 

harvest timber and establish tree reproduction simultaneously. Silvicultural techniques used to manage ponderosa pine forests in the Southwest produce stands with 

two types of age structure: even-aged and uneven-aged 

(Schubert 1974; Alexander and Edminster 1980). Regeneration techniques that mimic natural disturbance regimes 

lead to forests that are similar to "natural (unrnanaged) 

forests," which are generally uneven-aged. 

Even-Aged Management 

Under even-aged management, harvest and regeneration are planned by area and are a function of rotation 

age, which is the age at which a stand is considered to be 

regenerated on the basis of management objectives. Trees 

of a given stand are of one or two age classes. Sustained 

yield is maintained at the forest, not the stand, level 

(Alexander 1987). Historically, techniques leading to evenaged stand management have been favored for timber 

harvest on public lands in the Southwest for reasons of 

economy and efficiency (USDI Fish and Wildlife Service 

1995). Cutting methods traditionally used to harvest or 

regenerate stands under even-aged systems include: 1) the 

shelterwood method, which consists of the gradual removal of most or all trees in a series of partial cuttings 

extending over a portion of the rotation; 2) the seed tree 

method, which consists of removing all trees in a stand 

except a small number (left singly or in groups) to reseed 

the harvested area; and 3) the clearcutting method, which 

consists of harvesting the timber crop in one step to establish a new stand (USDA Forest Service 1983). 

Uneven-Aged Management 

Under uneven-aged management, individual trees or 

small groups of trees are selectively removed throughout 

the stand on the basis of age, diameter, vigor, form, and 

species to maintain a relatively consistent stand structure. 

The individual tree selection cutting method is used to 

produce uneven-aged stands, which regenerate continuously. The objective is to produce a stand with trees of 

different sizes and age classes intermingled on the same 

site (USDA Forest Service 1983). The group selection cutting method is also used to selectively harvest trees in 

groups from geographic areas ranging from a fraction of 

a hectare up to about 5 ha (USDA Forest Service 1983). 

The area cut is generally smaller than the minimum feasible for a single stand under even-aged management. 

Regeneration and Intermediate Treatments 

Following or during harvest, a ponderosa pine stand is 

treated to create conditions favorable for regeneration of 

desired species. Site preparation may involve removal of 

slash, preparation of a loose seedbed, and removal of the 

competing ground vegetation by mechanical, chemical, 

or burning treatments (Johnsen et al. 1973; Thompson et 

al. 1995). Slash may be removed to reduce the fuel load 

for wildfires or because it physically impedes stand regeneration or causes too much shade. Slash is commonly 

removed in combination with planting by means of broadcast burning, piling and burning, lopping and scattering, 

windrowing, or chopping on site. Seedbed preparation 

involves removing organic matter to expose mineral soil. 

Predominant methods of seedbed preparation include 

prescribed burning and scarification, which is the mechanical removal or mixing of the organic matter and the 

mineral soil. Competing vegetation is usually controlled 

by prescribed burning, mechanical treatment, or herbicides. Prescribed burning can also be used to encourage 

the growth of desired fire-adapted or dependent species 

(Thompson et al. 1995). 

Natural regeneration of ponderosa pine depends on 

moisture conditions. Since the seed of ponderosa pine often does not germinate until the coming of the summer 

rains, its vitality is impaired by the usual period of drought 

between April and June. The seedlings that do come up 

are subjected to another drought from the latter part of 

September to November (Woolsey 1911). Artificial regeneration is accomplished by planting young trees or by 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 29 
Chapter 2 

seeding before or after removing the old stand. This technique is often used with conifers because of low natural regeneration, high probability of successful artificial regeneration, and high financial yield (Thompson et al. 1995). 

Intermediate cuts include all the cutting treatments 

made from establishment of the new stand until replacement. Cuts are made when needed, but normally at specific intervals, to increase the quantity and quality of timber produced and to salvage material that would be lost. 

Common intermediate cuts in the Southwestern ponderosa pine forests include: 1) thinning, in which the smallest trees and rough dominants are removed; 2) release 

cutting, to release young trees from the competition of 

grass, brush, or trees to provide adequate growing space, 

light, and moisture for early rapid development; 3) improvement cutting, which resembles a sanitation-salvage 

cutting to improve the quality of the residual stand and 

reduce mortality; 4) sanitation cutting, which eliminates 

trees that have been attacked or are likely candidates for 

attack by insects or disease to prevent spread to other trees; 

and 5) salvage-cutting dead, dying, damaged, or deteriorating trees to derive economic benefits before decay processes reduce such values. Salvage cutting is a widespread 

practice often employed after insect outbreaks, fire, windstorms, and other natural disturbances (Schubert 1974; 

Thompson et al. 1995). 

History of Management of Ponderosa Pine 

Forests 

Prior to European settlement and management, the 

ponderosa pine forests in the Southwest were unevenaged, with the trees usually arranged by even-aged groups 

(Myers and Martin 1963). Since forest management began in the area, both even-aged and, to a lesser extent, 

uneven-aged systems have been used. In the early 1900s 

unmanaged ponderosa pine forests were converted to 

managed stands to maintain higher growing stock levels 

and timber production (Woolsey 1911; Pearson 1950; 

Myers and Martin 1963). 

The primitive application of the shelterwood method 

was the major harvest and regeneration practice used on 

widely adopted in the early and mid-1900s. Cutover areas were allowed to restock naturally regardless of the 

time required or the stocking achieved. Management intensity was increased by the 1970s. Managers were increasingly concerned with prompt restocking of cutover areas 

and with increasing the growth rate of the new stand by 

control of stand density. They sought to improve quantity and quality of yields by periodic thinning (Alexander 

and Edminster 1980). 

Silvicultural practices create edges and alter landscape 

structure, forest age, and structure that affect bird populations. Concern over these effects is often greater when 

timber is harvested on public forest lands since they are 

some of the least fragmented forests remaining in North 

America (Wilcove 1988; Thompson et al. 1995). The problems of meeting avian habitat needs while managing other 

forest resources on public lands became an important issue in selecting silvicultural practices in the late 1970s and 

early 1980s. A series of workshops and symposia were 

organized to bring together avian ecologists and forest 

resource managers to discuss common problems (see 

Smith 1975; DeGraff 1978,1980; McComb 1984). In the late 

1980s and early 1990s concern mounted over the effects 

of timber harvest on bird and other wildlife habitat, leading to court actions and legislatively mandated studies of 

habitat and wildlife populations on public land (USDI Fish 

and Wildlife Service 1995). A review of the status of current knowledge derived from these and other research 

projects and a discussion of critical future issues are presented in Martin and Finch (1995). 

To manage forests for habitat requirements of bird populations (as well as other species and resources), biologists 

now recommend a shift away from an over-emphasis on 

even-aged management strategies (Szaro and Balda 1979; 

Thompson et al. 1995; USDI Fish and Wildlife Service 

1995). They recommend a mix of silvicultural practices, 

including both even-aged and uneven-aged management 

strategies, that maximize landscape and regional diversity. A review of information gathered from bird community studies in Rocky Mountain habitats suggests that 

species respond individually to different silvicultural 

treatments. The authors (Hejl et al. 1995:236) state: 

ponderosa pine forest on ore st Service land in the South- . . . many forest birds were less abundant in west. Two-thirds of an original stand was cut and the re- clearcuts than in uncut forests, and species that mainder was removed when the new crop was established frequent open forests or open habitats were more (Woolsey 1911), which usually took 15 to 20 years. On abundant in clearcuts than in uncut forests. Most 

many of the federal forests, selective cuttings were made permanent residents were less abundant after in a series of light cuts, which generally amounted to the either kind of harvesting treatment (clearcut or shelterwood method (Clapp 1912; Pearson 1910). These partial logging), whereas about half the migrants light cuts eventually removed 60 to 70 percent of the volwere less abundant and half more abundant in 

ume, and the rest was cut 10 to 20 years later after re- harvested areas. production was established (Schubert 1974). 

"Loggers' selection" (high-grading), sanitation salvage, Thus, emphasizing any one silvicultural technique or 

and improvement selection cutting, which removed trees management strategy would favor some birds at the exin a series of cuts on an individual or group basis, were pense of others. Broad-scale management strategies and 

30 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Contemporary Human Use of Southwestern Ponderosa Pine Forests 

those that use many different techniques to mimic natural patterns and processes are recommended (Hejl et al. 

1995). Researchers urge that stand-level management 

should occur with knowledge of the regional status of the 

species and the ecosystem and that local-level management should complement regional goals (Hejl et al. 1995; 

Thompson et al. 1995). The goal, admittedly difficult and 

unattainable if too much is asked of the land, should be to 

manage the forest system for simultaneous production of 

goods and services in an optimal manner, while maintaining a healthy and balanced environment. 

Forest Changes and Silvicultural Practices 

Silvicultural practices have changed the availability, 

structure, and conformation of the ponderosa pine timberland in the Southwest. Silvicultural prescriptions have 

changed as our knowledge of forest ecologies has increased. Public opinion, political expediency, and individual personalities have also affected how the land has 

been managed, often irrespective of silvicultural requirements, site conditions, and conflicting objectives (Hejl et 

al. 1995). In-depth discussions of historical human activities and pre-European settlement conditions in ponderosa 

pine forests of the Southwest are presented in Scurlock 

(this volume) and Moir et al. (this volume). Thus, we focus here on presenting some of the more detailed information on changing forest condition and composition. 

In the following review, we use information gathered 

by the Forest Service since most ponderosa pine is under 

Forest Service management. Growth, mortality, and removals through harvest are the principal elements of 

change of ponderosa pine timberland in the Southwest 

today. Based on surveys conducted by the Forest Service 

in 1962 and 1986, it is estimated that the annual growth of 

ponderosa pine forests is about 4.62 million m3 in the 

Southwest. About 6 percent of the growing stock dies, 

leaving a net increase of 4.34 million m3

. If one subtracts 

an annual logging harvest (from those years) of 2.24 million m3

, the net annual addition is about 2.10 million m3. 

The causes of mortality in ponderosa pine that could be 

determined include insect infestation, disease, fire, animal damage, logging, suppression of growth by weather, 

and suppression by thinning and other silvicultural techniques (figure 2). In 1986, weather killed 72,000 m3 and 

disease accounted for another 14,000 m3. 

Ponderosa pine forests have always been the mainstay 

of the timber industry in the Southwest (Clapp 1912; 

Pearson 1910; Pearson and Marsh 1935). In New Mexico, 

about 73 percent of the lumber cut by sawmills has been 

ponderosa pine (Van Hooser 1993). Although other species have gradually become more important, ponderosa 

pine still accounted for 54 percent of the total lumber output for New Mexico in 1962. It increased to 69 percent in 

1986 (Choate 1966; Van Hooser et al. 1993). In 1986, 91 

Mortality of growing stock 

(in thousand cubic meters) 

Insect Disease Fire . Animal 

fl Weather . Suppression Logging Unknown 

Figure 2. Distribution of annual mortality of growing stock on 

ponderosa pine timberland by cause of death in Arizona and New Mexico (data summarized from Conner 

et a/. 1990; Van Hooser et al. 1993). 

percent of the 1.8 million m3 harvested in Arizona was 

ponderosa pine. In the two states combined, a total of 2.24 

million m3 of ponderosa pine was logged in 1986, and 

sawtimber trees accounted for 90 percent of the total cut. 

Based on surveys by Choate (1966), Spencer (1966), 

Conner et al. (1990), and Van Hooser et al. (1993), we found 

that in New Mexico and Arizona ponderosa pine accounted for 3.2 million ha of timber lands (78 percent of 

all the commercial forest types) in 1962 and 2.5 million ha 

in 1986 for a 22 percent decrease. This trend toward decrease is not consistent among stand classes. While the 

area of small tree stands (poletimber, sapling, and seedling) increased 238,000 ha or more than 2.5 times between 

1962 and 1986, sawtimber stands decreased 892,000 ha. 

The sawtimber stands accounted for 92 percent of 3.2 million ha of timberland in 1962 with a 10 percent reduction 

in the intervening 24 years (figure 3). Within the sawtimber stands, the volume of trees of dbh 243.2 cm (17 inches) 

decreased 992 million board feet, while the volume of trees 

of dbh below 43.2 cm increased 708 million board feet (figure 4). This resulted in a net decrease of 284 million board 

feet of sawtimber volume. The volume of growing stock 

showed similar trends between 1962 and 1986. The average growing stock volume of ponderosa pine timberland 

was 79 m3/ha in 1962 and 72 m3/ha in 1986 (figure 5). 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 2 

100 

80 

- 

a 

C 

60 

.m 

0 

C 

C 

a 

0 40 z 

n 

20 

0 Sawtimber Pdetimber Sspilngl~edling Nonstocked 

Stand size class 

Figure 3. Change of stand size of ponderosa pine timberland in 

Arizona and New Mexico between 1962 and 1986 

(data summarized from Choate 1966; Spencer 1966; 

Conner et al. 1990; Van Hooser et al. 1993). 

Because the general rule of historic logging was that 

the most accessible and commercially valuable trees were 

logged before less accessible and less valuable trees, logging and other silvicultural practices affected availability, structure, and species composition not only at the stand 

level, but also at the landscape level. For example, evenaged management creates a specific age-class distribution 

of forest habitats that usually differs from forests with no 

timber harvest. A common trend among forests managed 

under even-aged systems is that the oldest age classes are 

often absent because rotation ages are generally shorter 

than tree longevity. Depending on rotation age and frequency of natural disturbances, forests managed by evenaged management could have more or less early successional forest than natural landscapes (Thompson et al. 

1995). Even-aged management can result in an unnatural 

uniformity of habitat patch size and distribution, excluding small and very large patches. Our analysis suggests 

that current ponderosa pine forests in the Southwest contained more early successional forest in 1986 than in 1962. 

Contemporary Sawtimber Harvest 

In 1995,27 million board feet of ponderosa pine were 

cut on Forest Service lands in Arizona, while 3.7 million 

board feet were cut in New Mexico for a Region 3 total of 

over 30.8 million board feet. Ponderosa pine still is the 

largest component of the sawtimber cut from Forest Service lands in both states, though there have been changes 

in the size and number of commercial sawtimber sales. A 

comparison of the figures from 1979, the first year for 

maintaining the regional data base in the current format, 

with 1995 figures is instructive in this regard. In 1979,227 

Figure 4. 

8 1 

Tree size (d.b.h. cm) 

Change of sawtimber volume of ponderosa pine timberland in Arizona and New Mexico between 1962 and 

1986 (data summarized from Choate 1966; Spencer 

1966; Conner et al. 1990; Van Hooser et al. 1993). 

Tree size (d.b.h. cm) 

Figure 5. Change of growing stock volume of ponderosa pine 

timber stands in Arizona and New Mexico between 

1962 and 1986 (data summarized from Choate 1966; 

Spencer 1966; Conner et a/. 1990; Van Hooser et a/. 

1993). 

million board feet of ponderosa pine were cut on the forests of Region 3. In 1995, that figure was about 30.8 million board feet. The number of large sales over 2 million 

board feet has also dropped substantially over the years 

from 34 in 1979 to 5 in 1995. These declines have affected 

the commercial timber-related industries of Arizona and 

New Mexico. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Contemporary Human Use of Southwestern Ponderosa Pine Forests 

A Southwestern Region Forest Service white paper presents figures from 1984-1993 describing conditions and 

trends in the timber industry (USDA Forest Service Region 3 1994). During that period, the volume of all species 

cut declined from a high of 434 million board feet in 1989 

to a low of 159 million board feet in 1993. In 1995, the 

figure had declined further to 99.6 million board feet. Volume under contract also showed a steady decline throughout the period. In 1989, most of the major mills of the region were operating two shifts but were becoming 

concerned about the supply problem and were considering reducing to one shift. Toward the end of that year, 

several mills shut down for a short period and several 

reduced from two shifts to one owing to low volume under contract and market conditions. During this period, 

520 mill workers and 355 forestry workers were affected 

in New Mexico and Arizona (USDA Forest Service Region 3 1994). In the period from 1991 to 1993, all operating mills in New Mexico and Arizona reduced to one shift 

and eight shut down leaving about half the mill capacity 

that existed in 1984 (USDA Forest Service Region 3 1994). 

In 1984,24 large and small mills were listed by the Forest 

Service in the two states, excluding mills on Indian lands. 

By mid-1996, 10 were operating (Buddy Stewart, USFS 

Regional Economist, personal communication, 1996). 

Timber Industry in Rural Northern New Mexico 

Information from New Mexico provides an example of 

the role of the timber industry in local communities. 

Though the timber industry in the state is modest when 

viewed on a national scale, lumbering is a substantial 

business in New Mexico (Baker et al. 1988 cited in Van 

Hooser et al. 1993). In 1963,2,200 people-ane of every 

seven manufacturing workers-were employed in logging, 

milling, or some other wood products-related industry 

(Choate 1966). The number of jobs in the lumber and wood 

products sector peaked between 1972 and 1977 at 3,200 per 

year, or approximately 10 percent of the manufacturing jobs. 

By 1989, the number had declined to 2,500, or 6 percent of 

the manufacturing workforce (Van Hooser et al. 1993). 

Historically, almost two-thirds of the wood processing 

plants were located in the northern and central portions 

of the state (Van Hooser et al. 1993). Especially in the small, 

rural communities of the north, industries based on forest products have been major sources of employment. Six 

small mills that processed products from the Carson and 

Santa Fe National Forests have closed in the 1980s and 

1990s in places such as Chama, Alamosa (Colorado), Taos, 

Costilla, Espafiola, and Las Vegas (New Mexico). A larger 

mill operated by Duke City Lumber Company at Cuba 

was also shut down in 1992. Lack of supply was given as 

the reason for the closures (USDA Forest Service Region 3 

1994). In a pattern seen commonly across the state, timber industry officials often blame closings on the lack of 

Forest Service timber sales resulting from environmental 

legislation and litigation. Local environmental groups, on 

the other hand, stress the role of competition with timber 

coming in from Canada and the southeastern US. and 

alleged Forest Service mismanagement in the closings 

(Eichstaedt 1995; McClellan 1995; Toppo 1995; Korte 1996; 

Ragan 1996). 

Small-Scale Commercial and Personal-Use 

W~od Harvest 

The smaller scale harvest of both commercial and personal-use wood products is also important, even though 

these types of industries do not have the overall economic 

impact of large-scale, sawtimber harvests. Across the region in 1995, fuelwood formed the largest component of 

the non-sawtimber harvest from Forest Service lands followed by poles and posts. Christmas trees also comprise 

a substantial component. They are not discussed further 

here since ponderosa pine does not make up a large portion of this cut, ranking fourth well after pinyon, other 

softwoods, and true fir. 

The fuelwood cut for 1995 in Region 3 was 42.5 million 

board feet for both personal and commercial use. Poles 

accounted for 7.8 million board feet, while posts comprised 455,000 board feet. Of these cuts, ponderosa pine 

forms the largest component of the pole harvest at over 

4.5 million board feet with aspen forming the second largest component. With respect to both fuelwood and posts, 

ponderosa ranks second to pinyon and juniper. Of the 

large fuelwood harvest, ponderosa comprises only 3.3 

million board feet, while it makes up 61,500 board feet of 

the posts. As discussed by Van Hooser et al. (1993) for 

New Mexico, the pinyon-juniper woodlands provide the 

majority of the fuelwood and fenceposts for the state. Pinyon is the favored fuelwood for both heating and cooking 

because it burns hot and is long-lasting. Green pinyon is especially favored for these reasons. "Dead and down" ponderosa is also used, however, because of its availability as a 

byproduct of timber sales (Van Hooser et al. 1993). 

Fuelwood and small products harvests have the greatest potential to disturb bird habitat when they occur as 

unregulated activities. Habitat destruction and damage 

can occur through removal of snags, large downed logs 

(230 cm midpoint diameter), and particularly critical species (Brawn and Balda 1988; USDI Fish and Wildlife Service 1995). Poaching live trees, as well as snags and large 

downed logs, from undesignated areas are common occurrences in some locales that can threaten the integrity 

of bird habitat. In order to minimize negative impacts to 

habitat, fuelwood harvest should be regulated to control 

access and the kinds of materials that are taken. Designated harvest areas can be useful but may be difficult to 

enforce, especially in areas with a long tradition of ready 

access to forest resources and scant personnel for patrol 

(USDI Fish and Wildlife Service 1995). 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 33 
Chapter 2 

In many rural portions of the Southwest, fuelwood gathering is a necessity, not a luxury. Homes are often heated 

solely with wood and cooking is done on wood stoves. 

This is especially true of many rural areas of northern and 

central New Mexico. To complicate matters, much of the 

Forest Service land where the wood is gathered is former 

Spanish land grant land lost by the original owners in the 

aftermath of the Mexican War of 1846-1848 (Harper et al. 

1943; Eastman et al. 1971). Harvesting wood is considered to be a traditional "right" in these areas that ties the 

people of the villages back to their ancestral lands. Thus, 

many villagers often resent federal restrictions on land 

they consider to be rightfully theirs. 

A case in point is the local response to the federal injunction issued in August 1995 placing restrictions on logging and fuelwood harvesting on Forest Service land in 

Arizona and New Mexico to protect Mexican Spotted Owl 

habitat. The court ruling stemmed from a lawsuit filed by 

several environmental groups against the Forest Service, 

charging that the agency failed to consider adequately the 

cumulative impacts on the owl in planning its timber program. The resulting injunction restricting wood cutting 

and gathering hit the rural, primarily Hispanic, communities of northern New Mexico especially hard. Most of 

their heating and cooking wood comes from the Carson 

and Santa Fe National Forests. For example, since the early 

1700s people from the villages of Truchas, Las Trampas, 

and PeAasco have cut and gathered their fuelwood from 

the surrounding area-first from the Truchas Land Grant, 

and after portions of the grant became National Forest, 

from the Carson Forest (Eichstaedt 1995). Under Carson 

Forest policy, residents could obtain a permit to gather 

"dead and down" wood anywhere on the Forest and could 

even cut some snags. Part of the reason for allowing Forest-wide fuelwood harvesting, rare among Forests of Region 3, was that many of the wood gathering areas were 

part of the old land grant lost under U.S. takeover 

(Eichstaedt 1995). 

After the injunction, gathering "dead and down" wood 

was limited to specific marked areas, and the species of 

standing dead trees that could be cut were also limited 

(Eichstaedt 1995). No live or green trees could be cut, and 

sales of these types of trees were barred. Residents feared 

inadequate fuelwood supplies from the designated harvest areas, many of which were also farther away than 

local people normally travel to obtain wood (Ragan 1996). 

They were also concerned about job losses from the previously discussed mill closures (Ragan 1996). 

The villagers, as well as the loggers, lumber company 

officials, and sawmill owners and operators, blamed the 

environmentalists and the Forest Service for their plight. 

The environmentalists responded by blaming the Forest 

Service for inefficiency and mismanagement, and the big 

timber companies for greed. There were angry words and 

confrontations with charges of racism and "newcomerism" reported in both the local and national press 

(Eichstaedt 1995; McClellan 1995; Toppo 1995; Korte 1996). 

A new activist group, La Herencia de Nortefios Unidos, 

was formed to represent ranching, land, and logging interests in northern New Mexico. In late November 1995, 

the Herencia group staged a protest rally and hanged two 

Santa Fe environmental group leaders in effigy. Some lumber company officials and others with extractive interests 

on forest lands were also on hand to lend their support 

(~c~lellan 1995). 

After the rally the situation calmed somewhat. Discussions began between the opposing groups, and community drives and donations of wood (some from the 

"hanged" environmentalists) allayed most residents' fears 

about having sufficient wood to make it through the winter. Community leaders have urged compromise and understanding that would allow both protection of wildlife 

species and maintenance of traditional lifeways (de Buys 

1995). Whether or not compromises will be made remains 

to be seen, as does local community response to what are 

perceived as growing restrictions on forest use. These 

types of challenges are not unique to northern New Mexico 

but seem to occur with regularity throughout the West, as 

the economic orientation and values of local and newly 

arrived populations come into conflict. 

Livestock Grazing 

Livestock grazing in the ponderosa pine forest has a 

long history in Arizona and New Mexico and has been 

examined by various researchers. Range management in 

the ponderosa pine type of Arizona and prior range studies were discussed in detail by Clary (1975) and formed a 

portion of the symposium on Multiresource Management 

of Ponderosa Pine Forests, held in Flagstaff in 1989 (Tecle 

et al. 1989). Recently, several studies have reviewed the 

status of range research in varying geographic areas and 

vegetation types in terms of needed future direction 

(Evans 1990; Everett 1992; Kennedy et al. 1995; Vavra 1995). 

Understanding both the needs of wildlife and the needs 

of society concerning rangelands is mentioned as a key 

issue requiring study in the coming years (Kennedy et al. 

1995; Vavra 1995). 

Effect of Grazing on Bird Populations and 

Habitat 

Saab et al. (1995) reviewed research on the effect of cattle 

grazing on bird populations and habitat in western North 

America. Finch et al. (this volume) present a more specific review pertaining to the effects of livestock grazing 

on bird species in ponderosa pine. They state that the deUSDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Contemporary Human Use of Southwestern Ponderosa Pine Forests 

gree to which grazing affects habitat, and the birds using 

that habitat, relates to the number of animals grazing in 

an area (intensity), the timing of grazing, and the grazing 

system used. Not surprisingly, greater habitat changes 

occur as grazing intensity increases (Johnson 1956; Skovlin 

et al. 1976 cited in Finch et al. this volume). Grazing during the spring and early summer can directly affect reproductive success of breeding birds through destruction 

or disturbance of nests of ground or shrub nesting species (Finch et al. this volume). Heavy grazing during the 

growing season can also negatively affect regeneration of 

favored plant species. Vegetation in riparian areas may 

be especially susceptible since these zones are often overused by cattle in forested habitats (Samson 1980; Roath 

and Krueger 1982 a, b; Willard 1990 cited in Finch et al. 

this volume). 

Cattle compact soil by hoof action, remove plant materials, and indirectly reduce water infiltration, all of which 

can result in decreased vegetation density (Holecheck et 

a1 1989; Saab et al. 1995). Intense grazing pressure in coniferous forests, in conjunction with fire suppression, 

sometimes leads to enhanced establishment of conifer 

seedlings and consequent conversion of montane shrub, 

meadow, and grassland areas to forested habitat (Saab et 

al. 1995). As with varying responses to silvicultural treat- - - - 

ments, some bird species respond positively to the effects 

of cattle grazing while others respond negatively (Saab et 

al. 1995). 

From their literature reviews, both Saab et al. (1995) and 

Finch et al. (this volume) conclude that little is known 

about the effects of different grazing systems on bird habitat in western coniferous forests. Saab et al. (1995) speculate that birds most likely to be negatively affected by grazing are those that are dependent upon herbaceous and 

shrubby ground cover for nesting and/or foraging and 

those requiring open savannahs as opposed to closedcanopy forests. They also suggest that as a result of foraging, the diminished fine fuels reduce fire frequency which 

results in a decrease in fire-caused snags. This decrease 

would negatively affect primary and secondary cavity 

nesters (Saab et al. 1995). Research is needed, however, to 

confirm these suggestions. Species that have increased or 

decreased with grazing are reviewed in Finch et al. (this 

volume). 

Saab et al. (1995) recommend a concerted study effort 

to provide information where little currently exists concerning the impacts of grazing on neotropical migrants in 

western coniferous forests. They suggest monitoring, with 

attention to matched forest habitats differing in grazing 

regimes or grazing histories, as a means of supplying this 

much-needed data. In addition, studies which examine 

the status of bird habitat and populations in areas that 

have been both grazed and logged are much needed. We 

were unable to find reported studies from these types of 

areas. 

Grazing on National Forest Lands in Region 3 

Livestock grazing is a major, long-standing use of National Forest lands throughout the Southwe~t.~ Table 1 

gives figures on the numbers of permittees, animals, and 

animal unit months (AUMs) in Region 3 in 1995. An AUM 

is the amount of forage required to support a mature 1000 

lb cow or its equivalent for one month (USDA Forest Service 1996). 

vationally, Region 2 (Colorado, Nebraska, South Dakota, and eastern Wyoming) and Region 3 rank second 

only to Region 4 (southern Idaho, Nevada, Utah, and 

western Wyoming) in amount of grazing use based on 

permitted head months (the time in months livestock 

spend on Forest Service land). Table 2 presents figures on 

the Region 3 allotments with a vegetation type composed 

of 50 percent or greater ponderosa pine and mixed conifer in 1995. 

Of the 253 ponderosa pine-mixed conifer allotments in 

Region 3, we have information on the grazing system in 

use on 232 of them. Seven allotments have combination 

systems which are not discussed here, and the remainder 

do not have information on the grazing system. The systems in use are seasonal, rest rotation, deferred, and yearlong. Under a seasonal system, the allotment is grazed 

All range figures were obtained from the USDA Forest Service Southwestern Region 3, Regional Office, Albuquerque, New Mexico, with 

the help of Dave Stewart and George Martinez. George Martinez also 

obtained information from Region 3 Forests on the number of allotments in ponderosa pine and mixed conifer and the types of grazing 

systems used on those allotments. 

Table 1. Livestockgrazing by permittees on National Forests 

in Region 3, 19958. 

No. of No. of 

State permittees animals AUMs 

Arizona 469 137,830 1 ,I 13,230 

New Mexico 1066 90,585 791,953 

Total 1535 228,415 1,905,183 

a Figures obtained from the USDA Forest Service Southwestern Region 3, 

Regional Office. 

Table 2. Grazing allotments on National Forests in Region 3 

with a vegetation type consisting of 250% ponderosa pine 

and mixed conifer, 1 9958. 

No. of Ha of 

State allotments allotments AUMs 

Arizona 100 1,139,813 249,472 

New Mexico 153 1,248,185 195,041 

Total 253 2,387,998 444,513 

a Figures obtained from the USDA Forest Service Southwestern Region 3, 

Regional Office. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 35 
Chapter 2 

continuously throughout the growing season on an annual basis, while under a year-long system the allotment 

is grazed continuously throughout the year (Saab et al. 

1995). Under rest rotation, the allotment is divided into 

pastures or segments with one being rested (usually for 

12 months) while the others are grazed. The period of nonuse is rotated among the pastures. Under deferred rotation, at least one pasture is rested during part of the grazing season and the deferment is rotated among pastures 

in succeeding years. This system is often used to graze 

one pasture during the early part of the growing season 

and the remaining pastures later in the season (discussed 

in Saab et al. 1995). 

Region 3 has the following breakdown of systems in 

use on the ponderosa pine-mixed conifer allotments: yearlong-2 allotments, seasonal-54, rest rotation-69, and 

deferred-107. The year-long systems are in the southern 

part of New Mexico on the Lincoln and Gila National Forests, while the seasonal systems are concentrated in the 

northern part of New Mexico on the Carson and Santa Fe 

National Forests (43 of the seasonal systems). The remainder are scattered throughout the Region. In future studies, this type of information will be valuable for the kinds 

of research that are needed to assess the effect of different 

types of grazing systems on bird populations and habitat 

as discussed by Finch et al. (this volume). In addition to 

different grazing systems, the types of Southwestern 

ranching operations themselves also have a significant 

impact on wildlife habitat and management, as discussed 

in the following section. 

Commercial and Traditional Ranching 

Operations 

Throughout the West, the rural ranching lifestyle is a 

deeply rooted tradition. Ranching on public lands is a 

strong, though not universally appreciated, aspect of this 

tradition, as demonstrated by the recent congressional 

debates and public controversy over range and grazing 

fee reform (Richardson 1995; Varela 1996). Scurlock (this 

volume) describes the history and development of range 

resource use in Arizona and New Mexico, from its beginnings in 1598 with Spanish colonization and the introduction of domesticated herbivores. Range statistics from 

Region 3 show a fluctuating but generally downward 

trend in numbers of permittees, animals authorized to 

graze, and AUMs from 1982-1995. Numbers of permittees in both states have dropped by about 25 percent, while 

animals authorized to graze have dropped by roughly 25 

percent in Arizona and 20 percent in New Mexico. These 

declines relate to climatic and market fluctuations, consolidation of permits, and growing urbanization in the 

region. The larger commercial operations generally fare 

better than smaller ones in terms of profit and maximizing the opportunities of technological advances and additional land acquisitions (Clary 1975; Harris et al. 1995). 

Smaller commercial operations tend to be hit more heavily 

by environmental and market fluctuations. 

There are many small operations in the region, and 

many that can be considered non-commercial (or traditional) on the basis of herd size (Eastman and Gray 1987). 

According to a recent statement by Congressman Bill 

Richardson in the discussions over grazing fee and range 

reform, 70 percent of federal permittees (on lands from 

all agehcies) in New Mexico have fewer than 100 head 

(Richardson 1995), which is about the minimum size of a 

small commercially viable operation as discussed by 

Eastman and Gray (1987). The willingness of these ranchers to implement grazing system practices and range improvements that benefit wildlife habitat will definitely be 

a factor in the success of habitat management strategies. 

Small, traditional operations occur throughout the region but tend to be concentrated in the more mountainous, ponderosa pine zones, with a special clustering in the 

small Hispanic villages of northern and central New Mexico. 

Owning animals is a very important aspect of these operations. The animals provide the villagers with a means of 

reaffirming ties to their ancestral lands and heritage. In many 

cases, the extra buffer that the animals provide allows the 

family to remain in the ancestral, rural community and continue at least a part of the traditional lifestyle (Eastman et al. 

1971; Eastman and Gray 1987; William de Buys [personal 

communication] 1995; Raish 1996;Varela 1996). 

Herd sizes, goals, and methods of operation differ significantly between the small-scale, traditional ventures 

and even small, commercial cattle ranches. Average herd 

sizes for the traditional enterprises are around 19, while 

small commercial ranches have about 100 head. Making a 

profit is the number one goal of commercial ranchers (even 

small-scale ones), followed by maintaining a good quality of life. These producers tailor their methods to maximize profit by increasing production. They tend to seek 

out and adopt new practices and range improvements that 

increase production and the quality of the herds. They are 

willing to invest cash, borrow, and take risks in the hope 

of eventual profit (Eastman and Gray 1987). 

The small-scale, traditional operators, on the other hand, 

rank quality of life first, followed by avoidance of being 

forced out of ranching, with making a profit last on the 

list. These goals condition their behavior and methods of 

operation. They are less willing to invest cash in what they 

perceive to be risky improvements or new techniques that 

may not work out. New technology often requires considerable time and effort to learn, while the benefits to 

the very small operation may be limited. Any increases in 

operational costs hit this group harder than the commercial stock raisers who sell many more animals and realize 

greater profits with which to fund rising costs (Eastman 

and Gray 1987; Richardson 1995). Thus, the small-scale 

operators may oppose actions that increase the cost of their 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Contemporary Human Use of Southwestern Ponderosa Pine Forests 

operations, such as increases in grazing fees or range improvements mandated to improve environmental conditions. Since small operators are prevalent in the region, 

their education and cooperation on issues of wildlife improvements may be critical to the success of habitat management programs. 

Urbanization and Recreation 

The ponderosa pine forests of the Southwestern United 

States, although currently sparsely inhabited, are disproportionately affected by increasing human population. 

Many small towns have grown exponentially in the last 

three decades as tourism and retirement industries 

boomed. Moreover, cool temperatures and scenic beauty 

attract many recreationists to the forests, especially during the summer months when desert dwellers try to escape extreme temperatures. The importance of ponderosa 

pine forests as recreation sites indicates that the potential 

impacts of humans on the forest are likely to be far greater 

than resident population censuses alone might suggest. 

Human pressures on the ponderosa pine forest will certainly continue to increase. Urban populations are projected to increase (e.g., Anderson 1995), and recreation demands throughout the United States are projected to 

accelerate (Boyle and Samson 1985; Flather and Cordel 1995). 

Urban Growth in Ponderosa Pine Forests 

The ponderosa pine forests of Arizona and New Mexico 

are sparsely populated by full-time residents. Flagstaff, 

Arizona, is the largest city situated wholly in ponderosa 

pine. It occupied 164 km2 and held 50,000 residents in 1990 

(U.S. Census Bureau). However, from 1960 to the present, 

Flagstaff has grown tremendously and is currently increasing at a rate of 15 percent per year (figure 6). The Arizona 

Department of Economic Security projects its population 

will exceed 100,000 in the year 2040.3 

Flagstaff's growth is not unique among cities in ponderosa pine forests or adjacent pinyon-juniper woodlands. 

Other important urban centers in or adjacent to ponderosa pine are Santa Fe, New Mexico (primarily in pinyonjuniper), and Prescott, Arizona, both of which are increasing rapidly ( Fig. 6). Five smaller cities (Payson, Pinetop, 

Judy Burding (Flagstaff Chamber of Commerce), Joyce Wachter (U.S. 

Census Bureau), Colleen Marzluff (S.E.I.), and A1 Sanford (NM Institute of Mining and Technology) provided information on economic 

growth and population size in Southwestern cities. Britta Morner, Tah 

Yang, Bill Larsen, Lorie Long, and Buddy Stewart of the USDA Forest 

Service Southwestern Region 3 provided recreation use and occupancy data. 

- ~la~staff, AZ -e - Santa Fe, NM 

-4- Payson. AZ . -A -. Ruidoso, NM 

4.. Pinetop, AZ -v.. Showlow, AZ - Taos, NM 

- Grand Canyon, AZ - Chama, NM P 4 . Cloudcrofl. NM / \-+dV 

--v- Los Alarnos, NM 1 ..*.. Cuba. NM 

Year 

Figure 6. Human population changes in towns in and adjacent 

to ponderosa pine forests in Arizona and New Mexico. 

Towns experiencing growth are plotted in the top panel. 

Towns of relatively stable size are plotted in the lower 

panel. Data from the time records were kept until 1990 

and were provided by the U.S. Census Bureau Library. 

Data for 1995 were obtained from local chambers of 

commerce or city clerks. 

and Showlow in Arizona; and Ruidoso and Taos in New 

Mexico) are showing the first stages of rapid growth (figure 

6). Payson and Ruidoso will likely follow Flagstaff's steep 

trajectory in the next few decades. The economic fuel for 

much of this rapid growth in ponderosa pine forest cities is 

provided by retirees, tourists, and recreationists. 

Not all towns in ponderosa pine forest are increasing in 

size. In contrast to those in the top panel of figure 6, five 

towns appear relatively stable in size (lower panel of figure 6). They apparently have not grown because of their 

isolation and proximity to federal or private land that is 

unavailable for subdivision. In the interesting case of Los 

Alamos, New Mexico, which was built in 1942 to house 

those developing the atom bomb, the lack of growth has 

resulted because the U.S. Department of Energy has not 

expanded operations. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 2 

Recreation in Ponderosa Pine Forests 

The national trend toward increased recreation (Boyle 

and Samson 1985; Flather and Cordel 1995) is evident 

within the ponderosa pine forests of Arizona and New 

Mexico. Most significant in this respect is Grand Canyon 

National Park, which includes campgrounds, lodges, 

roads, and scenic viewpoints in the ponderosa pine forest 

of northern Arizona. Visitation to the Park has grown tremendously since its opening in 1915 (figure 7). Nearly 5 

million people visited the Park in 1995. Even if each person only stayed one day, and visitation was evenly spread 

throughout the year, over 13,500 visitors would have been 

present each day of 1995. In reality, most visitation is during the summer when numbers of visitors per day can 

reach a total half as large as Flagstaff's population. 

Recreational use of National Forests in Arizona and 

New Mexico is also on the rise. Specific figures have been 

recorded only recently and are unavailable by forest type. 

However, recreation in the region is primarily in ponderosa pine and is useful for defining trends and activities. 

Recreation use increased from 1992 to 1995 in Region 3; 

over 40 million visitor-days of recreation were recorded 

in 1995 (figure 8). Most visitors were viewing scenery or 

camping, picnicking, and swimming (figure 8). Non-motorized travel (hiking, horseback riding, and river raftYear 

Figure 7. Visitation to Grand Canyon National Park from 1915 

to 1995. Data were collected by the U. S. National Park 

Service. The visitor-per-day vehicle multipliers were 

updated during 1992. Visitation in 1995 was estimated 

to be reduced by 50,000 people due to a government 

shutdown. 

ing) has increased most rapidly, as also noted for the nation as a whole (Flather and Cordel 1995). Hunting, fishing, winter sports, and resort camping have remained 

fairly stable and include many fewer people than travel 

and camping (figure 8). Nonconsumptive wildlife recreation (bird watching, nature study/viewing/photography) has increased each year, but involves relatively few 

pe~ple.~ However, nonconsumptive activities can have 

significapt impacts on species of great interest if individuals of these species are disturbed repeatedly. 

Marzluff presents a detailed discussion of the effects of 

the various different types of recreational activities on bird 

populations and habitat in another section of this volume. 

He reviews motorized travel and viewing scenery; camping and picnicking; hiking, nature study, and wildlife 

photography; resorts and recreation residences; and winter sports and mechanized off-road travel in his discussion. This section also describes the types of research required to address the effects of both urbanization and 

recreation on songbirds in Southwestern ponderosa pine 

forests (Marzluff this volume). 

Increased recreational use of the National Forests has 

led to an expansion of public facilities. Current (1995) facilities have the capacity to hold over 130,000 visitors per 

day, up from 98,000 in 1990 (U.S. Forest Service Annual 

Mechanized travel & view scenery --- 

w 

-+-4 

Camping, picnicking, 8 swimming 

/ ~iking, horseback. 8 water travel 

&.A .--.-. -.-.-.-A 

/ Hunting and fshing 

Resorts, ?bins, 8 camps 

b-Y. -.*.... \.......-.A 

- Wnter --.*-7 sports a - ..-.. * +.-..-.* 

Nonconsumpthre wildlife use 

Year 

Figure 8. Recreation use in Region 3 of the USDA Forest Service (Arizona, New Mexico, and a small portion of 

Texas and Oklahoma). Data were collected by surveying visitors to local facilities. Data before 1992 were 

obtained with varying methods and are not directly 

comparable to those presented. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Contemporary Human Use of Southwestern Ponderosa Pine Forests 

Recreation Site and Area Information). The number of 

campgrounds and picnic areas increased slightly from 

1990 to 1995 (figure 9). The number of recreational residences in and adjacent to a National Forest has declined 

recently. Since Forest Service Region 3 recreation information is not maintained by vegetation type, it is difficult 

to determine the nature and extent of activities focusing 

in the ponderosa pine type. More research is needed on 

this topic, just as more research is needed concerning the 

effects of the various different types of recreational activities on bird species and habitat. 

Conclusion 

The issue of land use and its effects is a complex one. 

The environmental effects of a particular land use can be 

singular, synergistic, or cumulative with long- and shortterm consequences. Both synergistic and cumulative land 

use effects require considerably more research. An especially important area that should be targeted for future 

studies concerns the combined effects of logging and grazing on birds and bird habitat. 

Although we have focused primarily on human land 

uses and their negative effects to wildlife species, results 

of land use activities can also be positive or neutral for 

.- 1 - Number of campgrounds - Number of ~icnic sites 

.- c 1 I - Number of iesidences 

1- Total number of recreation sites 

0 1 1 I I I 

1990 1991 1992 1993 1994 1995 

Year 

Figure 9. Number of developed recreation sites in Region 3 of 

the USDA Forest Service. 

these species. Both Thompson et al. (1995) and Hejl et al. 

(1995) review positive, negative, and neutral effects of 

varying silvicultural treatments on selected species. Saab 

et al. (1995) provide a similar discussion with respect to 

grazing in western habitats. 

Since the 1960s and 1970s, the precedence of human 

resource consumption and use over other considerations 

has been under increasing scrutiny as demonstrated by 

environmental protection legislation and court actions. 

The'National Environmental Policy Act, the Endangered 

Species Act, the National Forest Management Act, and the 

Migratory Bird Treaty Act are examples of legislation designed to help protect the environment, as well as wildlife species and habitat. This legislation indicates the 

strength of the environmental movement and the general 

importance of wildlife protection to at least a certain segment of the American public. 

Despite the increase in environmental protection legislation, ponderosa pine habitat declined in geographic extent and tree volume in the period from 1962 through 1986 

in Arizona and New Mexico. Though the geographic extent and volume of small trees (poletimber, saplings, seedlings, and trees with a dbh below 43.2 cm) increased, these 

measures decreased for large trees, yielding an overall 

decrease. As discussed previously, logging is generally the 

prime cause of changes in stand geographic extent and 

volume (Choate 1966; Spencer 1966; Comer et al. 1990; Van 

Hooser et al. 1993). Historically, ponderosa pine has been a 

main, heavily cut component of the Southwestern timber 

harvest (Schubert 1974), and this pattern continued into the 

1980s. Since the beginning of the 1990s, both timber sales 

and cut volume of all species have declined on Forest Service land. Many factors contributed to these declines, including implementation of the Mexican Spotted Owl and Goshawk Habitat Protection Guidelines (USDA Forest Service 

Region 3 1994). The effect of these declines on the health and 

extent of ponderosa pine habitat remains to be seen. 

In addition to wood harvest, cattle grazing (as well as 

the grazing of wild herbivores such as elk) can alter ponderosa pine habitat. There is less information on the effects of grazing (Finch et al. this volume) than on the effects of timber cutting and even less on the combined 

effects of timber harvest and grazing. Grazing on public 

lands is now coming under increasing scrutiny and discussion. Recent congressional debates and public controversy over range and grazing fee reform show a changing, more negative public perception of ranching on 

federal lands (Kennedy et al. 1995; Richardson 1995; 

Mitchell and Fletcher 1996; Varela 1996). Judging the extent to which perceptions and attitudes of the general 

public differ from those of non-governmental organizations and advocacy groups is difficult and is becoming an 

area of concern to federal land managers (Mitchell and 

Fletcher 1996). In any event, there is growing awareness 

of the potentially harmful effects of grazing on birds and 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 2 

other wildlife species and recognition that future range 

studies must consider both the needs of wildlife and the 

needs of society if they are to be effective (Kennedy et al. 

1995; Vavra 1995). 

Since the 1920s and 1930s, there has been a downward 

trend in the number of animals grazing on public lands in 

the Southwest (discussed in Raish 1996). As discussed 

previously, in the years from 1982 through 1995 the numbers of Forest Service permittees dropped by about 25 

percent in Arizona and New Mexico, while the number 

of animals authorized to graze dropped by 25 percent in 

Arizona and 20 percent in New Mexico. However, the 

ways in which these figures relate to the various different 

grazing systems in use and the effects of these systems on 

wildlife and wildlife habitat are not well known. The effect of wild herbivore grazing in conjunction with cattle 

grazing is also a topic that requires additional research. 

Answering these questions requires a concerted program 

of study focusing on the effects of different grazing systems on wildlife in matched habitat types (Saab et al. 1995). 

In addition to studies focusing on the effects of cattle 

grazing, more information is needed on the effects of urbanization and recreation on wildlife species and habitat. 

With urban populations projected to increase and recreation demands projected to accelerate throughout the 

United States (Boyle and Samson 1985; Anderson 1995; 

Flather and Cordel 1995), the potential for considerable 

negative effects from these activities is high. Studies designed to assess the impacts of these types of activities 

can assist planners to prepare growth models and recreation development strategies that are the least harmful to 

species and habitat. 

Though there are indeed many human activities occurring in the ponderosa pine forests of the Southwest, this 

review has examined those that have the greatest potential to affect bird species and their habitat. Thus, commercial and personal-use wood harvest, livestock grazing, 

recreation, and urbanization have been considered. Of 

these, we have the greatest amount of research information on the effects of large-scale timber harvesting on habitat. Considerably more research is needed concerning the 

effects of different types of grazing systems and the effects of combined grazing and logging. Different types of 

recreational activities and growing urbanization in the 

region also require additional research. Studies of the effects of these activities are crucial for planning future developments that consider both human and wildlife needs. 

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USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 3 

A Historical Review 

Dan Scurlock and Deborah M. Finch 

Introduction 

Many groups of people in the Southwest have been 

closely associated with ponderosa pine forests for at least 

12,000 years. In the last 150 years, activities, such as logging, fire suppression, and grazing, have caused extensive modifications to ponderosa pine forests including 

changes in distribution, species composition, stand age, 

and a general decline in forest health. Climatic changes 

have also contributed to forest modification. Forest habitat alterations have affected the distribution and abundance of bird populations, resulting in population decreases or increases of some species. 

This chapter reviews the historical: 1) occupancy, use 

of and impacts on ponderosa pine forests by early American Indians and European settlers; and 2) the human use of 

and impacts on birds in ponderosa pine forests. Contemporary ecology and human use of ponderosa pine forests are 

described in this publication by Moir et al. and Raish et al. 

Recent human impacts on ponderosa pine birds are discussed 

by Marzluff and Finch, also in this volume. 

Historical Observations of 

Ponderosa Pine Forests 

Perhaps the first European to see a ponderosa pine forest in the Southwest United States was Alvar Nunez 

Cabeza de Vaca, who traveled across southeastern New 

his aimy eventually reached present Taos and Pecos, New 

Mexico. The term "pino" was used by the chronicler of 

the expedition when describing the trees observed. Reference was made to "pillars of pine," which may have 

been ponderosa pine, that were used by the Pueblo Indians to construct footbridges (Strout 1971). Extensive montane pine forests in the region were mentioned by Coronado, 

as they were by several subsequent Spanish explorers in the 

late 1500s. The earliest description of ponderosa pines in the 

region was by Don Pedro Baptista Pino in 1812, who remarked that the trees he observed were more than 110 ft tall 

and 14 to 19 ft thick (Bustamante and Simmons 1995). 

Descriptions of ponderosa pine forests in New Mexico 

and Arizona were made by early United States military 

personnel and scientists. Lt. James H. Simpson, on an 1849 

expedition at the present border of New Mexico and Arizona, referred to "yellow pine" describing them as "about 

eighty feet high and twelve feet in circumference at the 

trunk" (McNitt 1964). In 1853, Lt. A. W. Whipple described 

extensive pine forests on the flanks of the San Francisco 

Peaks. To the west of the range he observed, "groves of 

magnificent pines, intermingled with cedars and dwarf 

oaks" (Foreman 1946). Later, C. E. Dutton wrote about the 

ponderosa pine forests of the Kaibab Plateau in northern 

Arizona: 

"The trees are large and noble in aspect and stand 

widely apart . . . . Instead of dense forests, we 

can look far beyond and see the tree trunks vanishing away like an infinite colonnade" (quoted 

in Mitchell and Freeman 1993). 

C. Hart Merriam (1890) described the ponderosa pine forest on the Coconino Plateau. 

Mexico in 1536. Although Vaca did not specifically refer "The pine forest is thoroughly mature, nearly all to ponderosa pine, he did describe pinyon and another of the trees being of large size, and rarely pine growing in the region's mountains (Covey 1983). Fray crowded. It is a noteworthy forest, not alone on Marcos de Niza led a small expedition from western Mexico account of the size and beauty of the single spe- into present southeastern Arizona and then north in search cies of tree of which it is composed (Pinus ponde- of Pueblo Indians. Niza probably observed ponderosa pine rosa), but also because of its openness, freedom in eastern Arizona near the New Mexico border (Simmons 

1977). from undergrowth, and its grassy carpet. . . ." 

1nlate 1540, Francisco Vasquez de Coronado traveled This openness was also noted by Leiberg et al. (1904); 

north to the upper Rio Grande to reach Zuni Indian vil- however, by 1904, logging was fragmenting the extensive, 

lages. From there he marched east to present Socorro, New open stands of ponderosa pine. Cooper (1960) has pubMexico before joining a second contingent at a Pueblo vil- lished other similar historical descriptions of ponderosa 

lage near present Bernalillo, New Mexico. Coronado and pine forests. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 43 
Chapter 3 

Prehistoric and Historic Use of 

Ponderosa Pine Forests 

American Indian 

The first human contact with ponderosa pine forest occurred approximately 12,000 years ago when the earliest 

Paleo-Indians migrated south from Alaska and Canada 

into present Western United States. Although the groups 

that settled in this area over the next 5 millennia probably 

used ponderosa pine, its specific use in the Southwest was 

not archeologically documented until about 100 A.D. Initially, poles and small logs of ponderosa pine were used 

to construct the roofs of pithouses (semi-subterranean 

dome-shaped wooden structure with a roof of grass, sticks, 

and mud). Ponderosa pine was used as village architecture 

evolved into multiple-room surface structures and eventually into multi-storied, apartment-styled complexes after 950 

A.D. (Cordell 1984; Nabokov and Easton 1989). 

Many Anasazi village sites were located in pinyon-juniper woodlands where residents used nearby ponderosa 

pine stands for construction material. Ponderosa pine remains have been recorded at Arroyo Hondo Pueblo south 

of Santa Fe and at the Pajarito Plateau to the west. Chaco 

Canyon is the most extensive and best known prehistoric 

(12,000 B.P. to 1540) archeological site where ponderosa 

pine house beams have been found. The use of ponderosa pine by the prehistoric Pueblo for roof and other construction material continued into the historic period (1540 

to 1945). The Hohokam and Mogollon of southern Arizona used ponderosa pine to build roofs (Kelley 1980; 

Mindeleff 1891; Nabokov and Easton 1989). 

Although dead trees were generally used for fuelwood 

(Hughes 1983) and wood from older, abandoned rooms 

or villages was recycled into new construction (Ford 1987), 

living trees were harvested in certain locations. Packrat 

midden and pollen analyses at Chaco Canyon and Anasazi 

sites in Southwestern Colorado indicate that use of forest 

resources could be relatively intense, leading to soil erosion and other associated impacts that eventually caused 

village abandonment. Besides harvesting for construction 

timbers and fuelwood, the Anasazi also cleared relatively 

extensive acreage to farm (Betancourt and Van Devender 

1981; Petersen and Matthews 1987; Wyckoff 1977). 

At some large villages or village clusters, such as Chaco 

Canyon, ponderosa pine logs were widely used, especially 

as vigas (supporting rafters) in roof construction. Between 

1050 and 1125, approximately 100,000 ponderosa pine logs 

were cut in mountain ranges 45 to 60 miles away and 

hauled to Chaco villages where they were used in constructing the roofs of residential rooms and kivas (round, 

partly underground ceremonial structures). Area pinyonjuniper woodlands and sparse ponderosa pine forests 

were extensively harvested between 900 and 1125 for construction and fuelwood use (Betancourt and Van Devender 

1981; Hall 1977; Murphy 1994; Toll 1985). 

During the historic period, Pueblo uses of ponderosa 

pine included chewing the needles as a cold sore remedy, 

drinking a concentrate made from the roots to treat urinary 

problems, and making cradle boards. Ponderosa pine continued to be commonly used in construction and as fuelwood 

(Dunmire and Tierney 1995). The Hopi of northeastern Arizona usdd ponderosa pine from the San Francisco Peaks for 

prayer sticks and kiva roof beams (Houk 1993; Whiting 1966). 

The Navajo, Southern Ute, and various Apache tribes 

in the Southwest used the inner bark of the ponderosa 

pine (Castetter 1935), which was collected by removing a 

rectangular or oval patch of the scaly outer bark. The 

stringy layer of phloem and cambium cells was removed 

and eaten raw, made into a flour for bread making, and 

used to make a tea. Sap in the spring made the inner bark 

more palatable than at other times of the year when it was 

used only as an emergency food (Cassells 1983; Swetnam 

1984). The Utes placed those who were ill next to peeled 

ponderosa pine trees believing that doing so would help 

them recover (Cassells 1983). Trees scarred in the 18th, 19th, 

or early 20th centuries by this collecting activity are still visible on National Forest System (NFS) land in the Southwest. 

The Navajo, from their late prehistoric arrival in the 

Southwest until recently, have also used ponderosa pine as 

construction material in the hogan (a building made of logs 

and mud and used as a dwelling). Trees that were windfelled or lightning-struck were preferred, as was timber from 

prehistoric ruins or abandoned hogans; hogan sites were 

usually located in or close to ponderosa pine stands. Ponderosa pine was and is used by the Navajo for fencing. The 

Navajo used ponderosa pine for fuelwood (Jett and Spencer 

1981) and obtained a reddish dye and pigment from the bark, 

which they used in sand paintings (Houk 1993). 

European Settlers 

Spanish settlers used ponderosa pine wood for bv.ilding material, furniture, and tool handles. They extracted 

yellow dye from ponderosa pine to use in leather tanning 

and resin to treat scaly skin, smallpox, and liver spots 

(Boyd 1974; Curtin 1965). Although not as important as 

juniper and pinyon, ponderosa pine wood has and is used 

as a fuel. Ponderosa pine was used to make retablos (religious images painted on a piece of wood or metal) that 

were used as either part of an altar screen or as a decorative hanging in a home or business (Dickey 1970). 

Anglo-American settlers in northern New Mexico began to harvest ponderosa pine for construction and 

fuelwood in the late 1840s. Logging operations and sawmills were established across the region from the 1850s to 

the 1930s to meet the demand for timber at military posts, 

mine and railroad construction sites, and settlements. PonUSDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
A Historical Overview 

derosa pine has been cultivated in the West since 1827 and 

used as ornamental, shade, or shelter-belt plantings (Vines 

1960). 

Grazing 

New Mexico 

Livestock grazing and settlement began in the Southwest in 1598, when Juan de Oiiate led the first Spanish 

settlers and 4,000 sheep, 1,000 cattle, 1,000 goats, and 150 

mares with colts to the upper Rio Grande Basin in present 

New Mexico. Some of the wealthier individuals brought 

their own livestock (Baxter 1987; table 1). As these early 

herds grew, livestock grazing operations began at a number of missions and land grant (a grant of land made by 

the government) settlements in northern and central New 

Mexico. As early as 1630, overgrazing at these locations 

was documented (Baxter 1987; Ford 1987; Simmons 1991). 

Following the appearance of spring grasses and shrubs 

from the pinyon-juniper to the mixed conifer zones, sheep, 

goats, and cattle were moved from their lower, protected 

winter pastures and herded into the uplands. By early 

summer the stock was herded as high as subalpine meadows or to the tundra above 12,000 ft. These uplands, including pinyon-juniper woodlands and/or ponderosa 

pine forests, were ejidos (common lands) shared by the 

villagers (Bailey 1890; Briggs and Ness 1987). 

The development of livestock raising in New Mexico 

was interrupted for 13 years during the Pueblo Revolt of 

1680. In 1693, the Spaniards began raising livestock again 

with more than 4,000 sheep, cattle, and goats. By the 

middle of the next century, livestock numbers had increased to more than 135,000 animals, which were grazing 

from Taos to Belen, New Mexico (Baxter 1987; table 1). 

Montane woodlands and/or forests, part of every Spanish land grant in north central New Mexico, were intensively grazed from the 18th century until the mid-1800s. 

In the 18th century, some land grants in northern New 

Table 1. Livestock numbers in the Southwest, 1598-1820~.~ 

Year Sheep Cattle Goats Horses Mules Total 

a Does not include Navajo flocks. 

Includes Hopi flocks. 

Includes sheep. 

Data not recorded. 

Source: Baxter 1987; Denevan 1967; Simmons 1988. 

Mexico were awarded exclusively for grazing livestock 

(Bailey 1980; Briggs and Ness 1987). Meadows and springs 

were camping areas for herders and bedding grounds for 

goats and sheep (Scurlock 1983,1997). 

By the early 1700s, Navajos in northwestern New 

Mexico and northeastern Arizona had adopted Spanish 

sheep and herding techniques. Animal numbers ranged 

from 8,000 head in 1721 to 64,000 by 1742. A century later, 

the total number of Navajo sheep was estimated at 500,000. 

Thede numbers dropped dramatically to 30,000 in 1870 

following the reduction of American Indian land holdings and placement of many tribes in the reservation system. Through land allotment, American Indians resettled 

most of their former territory and again raised livestock. 

By 1930, Navajo flocks had increased to over 1 million 

sheep and goats. Horse and cattle numbers had also increased significantly to 80,000 and 27,000, respectively 

(Bailey 1980). 

Escaped horses and burros across the Southwest led to 

the increase of wild herds in the middle to late colonial 

period (1750-1821). Raids by nomadic American Indians 

also spread and increased the number of wild horses who 

ranged, in unknown numbers, into the ponderosa pine 

forests to graze. By the late 1700s, wild herds were locally 

abundant. The decline of wild horses, burros, and goats 

began in the 1860s with the arrival of Anglo-American 

ranchers who shot or captured wild horses that were competing with their cattle for grass and water (Bustamante 

and Simmons 1995; Wyman 1945). 

In the early BOOS, some 30,000 Spanish New Mexican 

sheep were exported annually to Mexico. By the 1820s, 

the number of sheep in New Mexico, excluding the Navajo herds, had increased to between 1 and 3 million head. 

Cattle numbered 5,000 head, horses 850, and mules 2,150. 

Apache and Navajo raids on sheep flocks reduced the 

sheep numbers to 377,000 by 1850 (table 2). Losses due to 

droughts, blizzards, and predators also contributed to the 

decline (Baxter 1987; Denevan 1967). 

Table 2. Livestock numbers in New Mexico, 1850-1900.a 

Year Sheep Cattle Total 

1850 377,000 b 377,000 

1860 830,000 b 830,000 

1870 619,000 137,314 756,314 

1880s 2,000,000 500,000 2,500,000 

to to 

5,400,000 5,000,000 

1890 4,000,000 210,000 1,517,000 

1900 3,500,000 843,OO 4,343,000 

1935 669,000 212,000 881,000 

a Does not include Navajo flocks. 

Data not recorded. 

Source: Baxter 1987; Carlson 1969; Dcnevan 1967; Miller 1989; Simmons 1988. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 45 
Chapter 3 

The first Anglo-American owned cattle were driven into 

New Mexico from Texas in 1865 and 1866 to supply beef 

to military posts and miners. In 1866, about 7,000 head of 

cattle were sold to the army, whose increasing demand 

for beef fueled the cattle drives in the late 1860s and 1870s 

from Texas to eastern and southern New Mexico. In 1870, 

there were over 137,000 cattle in New Mexico. Military 

contracts for beef from New Mexican ranchers ended in 

the early 1880s (Miller 1989). 

Cattle numbers grew to over a half million head by the 

early 1880s. Some ranchers were attracted to New Mexico 

following completion of 2 major rail lines in 1879 and 1881. 

Droughts and overgrazing in west Texas in the 1870s and 

1880s also caused many ranchers to drive their herds into 

New Mexico. Many of the Texas cattle herds that were 

moved to New Mexico grazed during the summer in the 

woodlands and forests of the Jemez, Sangre de Cristo, and 

other mountain ranges in northern and central New 

Mexico. Other herds went to southeast Arizona and southern Colorado (Scurlock 1997). 

In 1870, there were 619,000 sheep in New Mexico 

(Carlson 1969; table 2). These numbers reached an estimated peak of 4 to 5 million head in the 1880s. At the beginning of the 20th century, due to range deterioration 

caused by overgrazing and droughts, there was a decrease 

in sheep to 3.5 million. (Carlson 1969; deBuys 1985; 

Denevan 1967). Extensive grazing continued in New 

Mexico uplands until the end of the century. Passage of 

the General Revision Act on March 3, 1891, authorized 

the President of the United States to establish Forest Reserves (now called National Forests) on public land, in 

any state or territory, wholly of partly covered with timber or undergrowth with or without commercial value. 

Many local residents who lost their grazing rights to the 

previously common land, continued to graze their stock 

on the Forest Reserve land (Bahre 1991; Carlson 1969; 

deBuys 1985). By 1938, about 203,000 sheep were grazing 

during the summer on public and private lands in northern New Mexico (Workers of the Writers' Program 1940a). 

Arizona 

The first livestock in Arizona was brought by Franciscan 

missionaries to the Hopi Pueblo in 1629. Herds of sheep, 

goats, cattle, oxen, horses, and burros were grazed around 

the Hopi missions and villages for the next 50 years. By the 

early 1700s, the Hopi were raising their own livestock; one 

of the pueblos had 30,000 sheep in 1776 (Schickedanz 1980). 

The Spanish brought the first herds of livestock into 

southern Arizona after 1690. Missions were established 

with herds of primarily sheep and cattle. Spanish ranching operations were also established in the Santa Cruz and 

San Pedro drainages (Faulk 1970). Some 100,000 head of 

cattle were grazing on the headwaters of the San Pedro in 

southern Arizona in 1694 (Schickedanz 1980). However, 

Apache raids on Spanish livestock during much of the 

1700s prevented settlement of new ranches and kept the 

number of herds low. In the early 1800s, there were 26,000 

sheep and 1,200 horses grazing around Tucson and 1,000 

cattle grazing at Tubac. Several Arizona land grants were 

made in the first 2 decades of the century; one near San 

Bernardino on the Mexican border grazed 100,000 head 

of cattle (Faulk 1970). By the early 1820s, large cattle herds 

were grazing at these locations, but Apache raids forced 

many tqabandon their ranches. Thousands of abandoned 

cattle became feral and roamed the area into the 1850s 

(Hirt 1989; Workers of the Writers' Program 1940b). 

One Spanish rancher grazed 10,000 sheep and 600 goats 

in southern Arizona in the mid-1800s. One of the earliest 

Anglo-American ranch was established on the Santa Cruz 

River in 1857; another small ranch began operating south 

of Tucson in 1858. The Apaches increased their livestock 

raids, which discouraged upland grazing (Hirt 1989). 

To the north, on the pinyon-juniper and ponderosa pinecovered Defiance Plateau, the Navajo began herding 

sheep, cattle, and horses, mules, and burros in the late 

1700s. By 1850, about 500,000 sheep, 30,000 cattle, and 

10,000 horses, mules and burros were grazing on the plateau. At the same time, the ponderosa pine and conifer 

forest understories of the Chuska Mountains were intensively grazed by relatively large sheep and other livestock 

herds (Bailey 1980; Cooper 1960). 

United States military posts, mine activity, and settlement growth, increased the demand for beef and mutton, 

which produced significant growth in southern Arizona's 

ranching industry (Pratt and Scurlock 1991). The military 

continued to contract with Arizona ranchers until the mid1870s. Navajo herds numbered about 225,000 head in 1873. 

Sheep herds were moved from California and New Mexico 

to new operations in northern Arizona beginning in the 

late 1860s and early 1870s. 

In 1880, there were 8,000 cattle and 10,000 to 12,000 

sheep in the San Pedro Valley, Arizona. The arrival of railroads in the early 1880s caused livestock numbers across 

most of Arizona to rapidly increase. One sheep rancher 

near Flagstaff had 50,000 animals grazing in the mid-1880s. 

By the end of the decade, many ranges were overstocked 

as the total number of cattle rose from 5,000 head in 1870 

to 8,000 head in 1880 to more than a half million head in 

1890. By 1891, there were more than 700,000 head of sheep 

in Arizona. When a drought struck the overgrazed range 

in 1891, livestock losses averaged 50 to 75 percent in southeastern Arizona. 

Introduction of livestock and overgrazing continued on 

private and public lands into the next century. Sheep outnumbered cattle 10 to 1 in northeastern Arizona, partly 

due to new Navajo flocks; cattle were common in the south. 

By 1938, there were 367,000 head of cattle shipped out of 

Arizona; some 121,000 more were slaughtered in Arizona. 

There were an estimated 811,000 sheep in the state that 

same year, with about half of this total on Navajo range46 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
A Historical Overview 

land (Bahre 1991; Hirt 1989; Workers of the Writers' Program Table 3. Grazing leases and livestock numbers in the 

1940b; Bailey 1980; Cooper 1960; Faulk 1970; Miller 1989). South west, 1909.1 958. 

National Forests 

By the time the first Forest Reserves were established 

in New Mexico and Arizona in the 1890s, most of the understory in accessible ponderosa pine forests had been 

intensively grazed. Although ranchers thought that free 

use of public land was a right and stocking was heavy, 

most realized that limiting herd size on Forest Reserve 

land was necessary to continue business (Baker et al. 1988; 

Eastman and Gray 1987). 

From 1893 to 1902,8 Forest Reserves were established 

in Arizona including Grand Canyon, Prescott, San Francisco Mountains, Black Mesa, Santa Rita, Santa Catalina, 

Mount Graham, and Chiricahua. These are now part of 

the Kaibab and Coconino National Forests, Prescott National Forest, Coconino National Forest, Coconino and 

Sitgreaves National Forests, and Coronado National Forest, respectively (Baker et al. 1988). Twelve more Forest 

Reserves were added from 1905 to 1906. 

In 1900, while surveying grazing at the headwaters of 

the upper Salt River and its affects on the lower valley, 

Gifford Pinchot, head of the Bureau of Forestry (now called 

the Forest Service) in the Department of Agriculture, noted 

that sheep overgrazing had destroyed young ponderosa 

pine seedlings (Frome 1962). Although grazing permits 

for horses and sheep were issued by the Bureau of Forestry during this period, it was not until 1906 that fees 

were collected for all livestock grazed on the Forest Reserves. From 1901 to 1906, there were 581 permits issued 

for approximately 98,000 cattle and horses, and 87 permits issued for approxmately 347,000 sheep and goats to 

graze on Forest Reserves in Arizona (Rowley 1985). 

In the early years of the 20th century, heavy stocking of 

Forest Reserves was thought a viable way to reduce vegetation and diminish the fire threat. Protests, noncompliance, and trespass by ranchers hindered effective management of grazing lands (Eastman and Gray 1987; Rowley 

1985). Additionally, the demand for food and wool during 

World War I caused livestock numbers to soar on public and 

private lands (Brown 1985; deBuys 1985; Donart 1984). 

The Forest Service began to reduce the number of permitted livestock on NFS land in the Southwest due to extreme range deterioration and erosion caused by overgrazing; numbers went from approximately 738,000 in 1919 to 

less than 536,000 in 1929 (Baker et al. 1988; table 3). Many 

ranchers in the Southwest sold their livestock during the 

post-war agricultural depression from 1919 to 1921, which 

further reduced the grazing numbers. Over the remainder of the decade, livestock numbers on NFS land continued to decline. This reduction in numbers grazed and 

permitted continued into the 1950s (table 3). Increases in 

grazing fees continued to be controversial (Baker et al. 

1988; Rowley 1985). 

Cattle and Sheep and 

Year Permit horses goats Total 

1909 3,m 235,946 512,130 748,076 

1914 3,321 270,623 398,134 688,766 

1919 3,590 366,520 371,457 737,977 

1924, 3,032 279,520 262,492 542,012 

1929 a 183,076 352,618 535,694 

1934 3,l 70 189,299 245,189 437,658 

1 3,886 371,862 

1 3,504 266,721 

1 a a 

1958 2,538 145,247 75,217 223,002 

a Data not recorded. 

Source: Baker et al. 1988. 

In an ,attempt to reduce grazing pressure by trespass 

livestock, fencing of NFS land began in the 1930s and continued into the 1940s. Passage of the Taylor Grazing Act 

of 1934 was prompted by overgrazing on NFS and Grazing Service (later called the Bureau of Land Management) 

land. This grazing regulation program resulted in a significant reduction of livestock numbers on public and 

Pueblo and Navajo land (Bahre 1991; deBuys 1985; 

Mortensen 1978). 

From the 1920s to the 1940s, Forest Service permittees 

typically grazed more animals than authorized. Also, large 

livestock operations were buying permits from smaller 

ranchers. The Forest Service stepped up enforcement to 

correct these 2 problems. In additiion, to prevent control 

of large areas of rangeland by a small number of individuals, the agency began limiting the maximum number of animals that could be grazed on a single permit. 

On the Carson and Santa Fe National Forests in New 

Mexico, the maximum number of animals authorized to 

graze on 1 permit was 400. In the 1940s, ranchers in New 

Mexico and southern Colorado began to abandon laborintensive sheep herding in favor of cattle, which range 

without herders. Changing economics also resulted in a 

steady decline in the number of permittees on forest lands 

(deBuys 1985). 

Forest Service reports for the 1950s through 1960s on 

ponderosa pine grasslands were mixed. According to a 

1952 study, ranges on the Kaibab National Forest were 

improving. A 1964 report noted that the Santa Fe National 

Forest was overstocked by 20 percent, while a report issued in 1965 for the Lincoln National Forest indicated that 

range management was improving. Inspectors found that 

many areas of Coronado National Forest were in unsatisfactory conditions (Baker et al. 1988). 

Grazing pressure during this period also resulted from 

feral horses and burros. Many of these animals sought 

secluded ranges in the uplands of Southwestern NFS, 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 47 
Chapter 3 

Bureau of Land Management (BLM) and National Park 

Service (NPS) land. Although the Forest Service, BLM, and 

NPS began round-ups and reductions in the early part of 

this century, some animals eluded their efforts. Small herds 

of horses and burros continue to exist on public and 

Ameican Indian reservation lands in the Southwest (Bahre 

1991; deBuys 1985; Symanski 1985). 

The long-lasting effect of overgrazing on NFS land during this century was noted in a 1986 Environmental Impact Statement for the grasslands of the Coronado National Forest. The observation was that, "The grazed 

portion of the range was severely overgrazed" [in 19021 

and "to this day ranges show signs of stress" (quoted in 

Hirt 1989). 

Logging 

Prehistoric Indian harvesting of ponderosa pine timber 

was localized. However, extensive use of ponderosa and 

pinyon pine at Chaco Canyon and other prehistoric population centers between 900 and 1125 resulted in severe 

environmental degradation. More than 100,000 trees were 

cut in at least 3 distant mountain ranges and hauled back 

to Chaco between 1000 and 1125. At other large village 

complexes (Mogollon, Hohokam, and Hakataya) ponderosa and pinyon pine species were commonly used to construct jacales (a hut in the Southwestern United States with 

a thatched roof and walls made of upright poles covered 

with mud or clay), pithouses, or surface houses (Gumerman and Haury 1979; Martin 1979; Schroeder 1979). Both 

ponderosa and pinyon pine were used to construct and 

renovate hundreds of other post- 500 to 1500 small, prehistoric sites in the Southwest. 

Logging by Spainish settlers during the colonial period 

(1540 to 1821) was limited to local forests near either landgrant villages or mission churches, where the surrounding pinyon juniper woodlands and ponderosa pine forests were commonly exploited. As nearby fuelwood was 

exhausted, pack mules, burros, and horses transported 

wood from increasingly greater distances (Adams and 

Chavez 1956; Fogg 1966). Ponderosa pine was often found 

in central and northern New Mexico on common land 

where resources were available for use by the Spanish land 

grantees. Early mission establishments among the Pueblo, 

including the Hopi of northeastern Arizona, also used 

ponderosa pine for building and fuelwood but impacts 

were limited to small areas (Jones 1932; Scurlock 1997). In 

southern Arizona, ponderosa pine use was minimal because Spanish land grants and missions, which all dated 

from the late colonial and Mexican (1821 to 1846) periods, 

were generally not near ponderosa pine forests. 

The first Anglo-American people who arrived in the 

Southwest in the 1820s and 1830s were fur trappers and 

traders. Some settled in northern or central New Mexico 

and southern Arizona. Their small numbers and lifestyle 

generated minimal impact to ponderosa pine forests, 

which they used primarily as a source of fuelwood (Weber 1971). 

In 1846, at the beginning of the Mexican War, the United 

States Army began to establish forts in the Southwest. 

Posts were established across Arizona and New Mexico 

over the next 2 decades to protect European settlers against 

American Indian tribes. Construction and occupation of 

these forts required lumber and fuelwood. The military 

set up sawmills or contracted for needed material. Wood 

cutting' by military troops also provided fuel and timber 

(Giese 1976; Miller 1989; Walker and Bufkin 1979). 

Mining in territorial New Mexico and Arizona (1846 to 

1880) and construction of the early railroads to New 

Mexico and Arizona (1879 to 1881) resulted in the first 

major commercial use of pinyon and ponderosa pine and 

juniper in the historic period (Scurlock 1997; Walker and 

Bufkin 1979). Harvesting ponderosa pine for railroad ties, 

mine timbers, or lumber caused local reduction in woodlands and forests in the late 19th century. One railroad 

company constructing a line across New Mexico in 1885, 

used over 930,000 ft of "native pine," which included pinyon and ponderosa (Christiansen 1974; Hirt 1989; Ensign 

1888; Perry 1922; Tratman 1889). A logging-sawmill operation was established in the Chiricahua Mountains in 

1879 and by 1902,ll sawmills were operating. About 30 

percent of the coniferous forest in the Chiricahuas was 

logged by 1902 (Bahre 1991). 

Timber consumption in New Mexico and Arizona 

steadily increased over the last 4 decades of the 19th century. Approximately 8 million board feet (MBF) and 22 

MBF was cut in 1869 and 1879, respectively. An estimated 

5 MBF of lumber was consumed in New Mexico alone in 

1886. By 1900, the annual cut in Arizona and New Mexico 

was 67 MBF (Houk 1993; table 4). Although fuelwood 

cutting was extensive during this period, little or no ponderosa pine was harvested. 

Authorized timber sales from Forests Reserves began 

in 1897, but the harvest was limited to $100 worth of timber per year for each permitee. Free use of dead timber 

was permitted. The Forest Service began timber sales on 

the 25 reserves in Arizona and New Mexico in fiscal year 

1906. Regulations limiting the cut remained until after 

1907, when 5 more National Forests (passage of the Act of 

March 4,1907, renamed the Forest Reserves) were established in Arizona and New Mexico (Baker et al. 1988); 

however, unauthorized cutting was widespread. Millions 

of board feet were illegally cut in the Prescott Forest Reserve in the early years of the century and by 1908, most 

of the timber in the Manzano National Forest had been 

harvested illegally for use as railroad construction material (Baker et al. 1988). 

In 1907, there was 90 MBF of standing ponderosa pine 

on the San Francisco Mountains Reserve, now part of the 

Coconino National Forest in Arizona. That year, this timber was cut and sold, enough mature trees were left to 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
A Historical Overview 

Table 4. TimbeP consumption in Arizona and New Mexico, 

1869- 1992. 

Year Lumber production (million board feet) 

a Primarily ponderosa pine. 

Fiscal year, October 1 - September 30. 

Source: Baker et al. 1988; Houk 1993. 

seed the cut areas, and a sufficient number of young trees 

were left to ensure a future cut. Ponderosa pine was also 

being cut on the Kaibab Plateau. The mill at Fredonia processed about 20 MBF of timber annually from 1910 to 1912. 

From 1912 to 1926, there were several lumber and timber 

companies operating in the Flagstaff-Williams area that 

processed logs from north central Arizona (Tucker and 

Fitzpatrick 1972). 

From 1912 to 1914, intensive logging occurred on 

Penasco Hill in the Carson National Forest. This operation was producing railroad ties for a second set of tracks 

across northern New Mexico. The Santa Barbara Pole and 

Tie Company was established in 1909 in the Santa Fe National Forest. From 1909 to 1926, all of the trees suitable 

for making railroad ties from the pinyon-juniper zone to 

the spruce-fir zone were cut on approximately 66,000 acres 

of this forest (deBuys 1985). 

During the latter part of World War I (1916-1918), logging of ponderosa pine in the Southwest increased sharply 

to meet United States market demands (table 4). Some 6 

billion board feet (BBF) of lumber was consumed during 

the United States war involvement. The regional lumber 

industry experienced a sharp production decline in 1920 

and 1921, but recovered quickly. Timber cutting, mostly 

ponderosa pine, increased during the remainder of the 

1920s (Baker et al. 1988). Sawmills and lumber companies 

operated in north central Arizona, primarily in the 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 

Coconino National Forest. The Apache Lumber Company 

purchased 600 MBF in the Sitgreaves and Apache National 

Forests in 1919 and 1920 (Baker et al. 1988). 

Every accessible ponderosa pine forest in New Mexico 

and Arizona was heavily logged in the 1930s and 1940s. 

Only stands on steep slopes were spared in Southwestern 

public and private forests. Logging activity increased 

during World War 11; from 1942 through 1946, the War 

Department purchased about 8 BBF per year. New Mexico 

and Arizona contributed from over 242 million to almost 

385 MBF during this period (table 4). The Fort Apache 

Indian Reservation was a major timber source, where over 

445 MBF, mainly ponderosa pine, was harvested in 1943. 

About 75 percent of the 675,000-acre reservation was covered by ponderosa pine (Gomez and Tier 1990; Lindh 1949). 

In 1941, there were 72 lumber mills in the upper Rio 

Grande Basin, New Mexico. These operations processed 

60 MBF that year, where 94 percent of the harvest was 

ponderosa pine. By 1950, the annual cut increased to 70 

MBF. This cut was more than 25 percent greater than the 

net annual tree growth in the watershed (Dortignac 1956). 

In 1948, ponderosa pine accounted for 88 percent of the 

total commercial species cut in the Southwest (Lindh 1949). 

In 1955, almost 246 MBF of lumber was harvested from 

public and private lands in New Mexico (Anonymous 

1959). Timber production for New Mexico and Arizona in 

1964 exceeded 399 MBF (table 4). A decline occurred from 

1972 to 1984, but by 1990 a record high of 433 MBF was 

reached (Baker et al. 1988; Houk 1993). Due to growing 

concerns for threatened, endangered, and sensitive species and their habitat, timber harvest on NFS land dropped 

to 145 MBF in 1992 (Houk 1993). 

Prehistoric and Historic 

Ecological Disturbances 

Before European settlement, naturally occurring and 

human-caused fire in ponderosa pine forests was a relatively frequent change agent. Fires, combined with 

drought, wet years, periodic regeneration, localized clearing, logging, and wood collecting, produced a complex 

mosaic in the distribution, age, structure, and composition of Southwestern ponderosa pine forests (Covington 

and Moore 1994). 

Fire 

Observations from 1850 to 1900, report an understory 

of abundant or luxuriant bunch grass species in ponderosa pine forests. This vegetation subcommunity generally existed from the beginning of the colonial period to 
Chapter 3 

the early part of this century. This condition, as well as 

scattered grassy "parks," was maintained by relatively 

frequent (every 2 to 12 years), low intensity fires and light 

grazing by indigenous mammals. Interspersed among 

these grasses were various annual or perennial herbaceous 

species. Soil erosion was minimal (Cooper 1960). Crown 

fires in mature timber were rare and some seedlings escaped ground fires. Young trees were generally killed in 

logged areas as the unburned slash burned hot during 

fires. Ground fires caused little damage due to "little underbrush and litter" (Plummer 1904). 

The effects of fire, both human-caused and natural, and 

other factors on ponderosa pine forests over the past 150 

years have been of interest to a number of investigators in 

the last 4 decades. Among those who have documented 

change in the range, structure, and floral composition of historic ponderosa pine forests are Cooper (1960), Johnson 

(1995), Covington and Moore (1994), and Weaver (1951). 

Weaver (1951) wrote, "Older whites and Jhdians remember 

when the ground under the ponderosa pines was grassy, 

open, and park-like, with but few windfalls, snags, and other 

debris." He concluded that fire was a significant factor in 

the development and maintenance of these conditions in 

ponderosa pine forests and that the subsequent change was 

caused by fire suppression beginning in the late 1800s. A 

policy of fire suppression was adopted for the Forest Reserves beginning in the 1890s, but effective fire control was 

not developed until after 1900. In that year, a fire in the Santa 

Fe Forest Reserve burned 40,000 acres (Baker et al. 1988). 

Dominance of Gambel oak, New Mexico locust, or pinyon-juniper occur following ponderosa pine stand-replacing fires or clear-cutting in some mountain ranges in the 

northern areas of the region. In the southern portion of 

the Southwest, ponderosa pine and gray oak or silverleaf 

oak occur. Associated aspen stand acreage has decreased 

significantly due primarily to fire suppression (DickPeddie 1993). Fire suppression and other human activities have also created oak-juniper thickets or young blackjack pine stands. Fire suppression, intensive livestock 

grazing, and/or logging, combined with periodic drought, 

led to regeneration of stands of dense, young pine, commonly called "dog hair thickets." Limited or no seedling 

regeneration, soil erosion, crown fires, structural changes, 

and a general decline of forest health also result from fire 

suppression (Cooper 1960; Covington and Moore 1994; 

Saab et al. 1995). Recently, ponderosa pine loss due to 

dwarf mistletoe and bark beetle epidemics, once regulated 

by periodic fires, has increased significantly (Harrington 

and Sackett 1992; Johnson 1995). 

Other changes in ponderosa pine forest attributed to 

fire suppression include "decreased decomposition rates, 

stagnated nutrient cycles, eruption of insects and diseases, 

decreased herbaceous and shrub forage quality and quantity, ecosystem simplification, increased vertical fuel continuity due to dense sampling and pole patches, higher 

severity and destructive potential of wildfire, decreased 

stream flow and on-site water balance, and less wildlife 

habitat for species dependent on herbaceous vegetation, 

and greater canopy closure and landscape homogeneity" 

(Covington and Moore 1994). 

Drought 

Drou ht, combined with changes in fire regime, grazing, an d logging, have produced significant changes in 

Southwestern ponderosa pine forests. The drought from 

1896 to 1904 in east central Arizona was severe, killing 

some ponderosa pine and alligator juniper. Recent, extended droughts, such as the one in the early to mid-1950s, 

killed juniper and ponderosa pine in the region including 

the Sevilleta National Wildlife Refuge in central New 

Mexico. Both of these climatic events resulted in the ponderosa pine zone spreading to higher elevations (Plummer 

1904; Scurlock 1996). In contrast, the wet year of 1919 was 

a time of exceptional ponderosa pine regeneration. 

Grazing 

As mentioned, the beginning of Spanish settlement and 

livestock grazing in the Southwest in 1598 brought dramatic changes to riparian, bajada (a long, gradual slope), 

mesa, mountain grasslands, and other vegetative communities. Grasses and shrubs were decimated by sheep, goats, 

cattle, and horses for up to several miles around major 

settlements. Removal of ground cover, soil compaction 

due to trampling, and droughts, resulted in severe, local 

sheet erosion and gullying (Ford 1987; MacCameron 1994). 

Early in the century, Leiberg et al. (1904) documented 

livestock damage to seedling ponderosa pine and young 

aspen shoots. Cattle and sheep trampled young trees, especially in riparian areas. When the grass cover was 

sparse, sheep nibbled seedlings, which caused stunting. 

However, goats were the most destructive. 

A study of grass plots excluded from grazing for 25 

years in ponderosa pine at several National Forests in New 

Mexico, showed a marked increase in blue grama, Arizona fescue, prairie junegrass, and creeping muhly. Forbs 

and browse cover increased, but under grazing conditions 

browse increase was inhibited. Ponderosa pine increased 

when protected from grazing (Potter and Krenetsky 1967). 

More recent studies of ponderosa pine forests have 

shown that livestock grazing, combined with fire suppression, resulted in denser stands of trees and shrubs that 

spread due to denudation of understory grass cover (Saab 

et al. 1995). 

Logging 

As mentioned, many ponderosa pine forests in the region were extensively cut from the 1870s to the 1940s. In 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1907 
A Historical Overview 

1898, the US. Geological Survey appraised regional forests and estimated that 19 percent of New Mexico and 22 

percent of Arizona were forested. By 1924, these figures 

had decreased due to logging to approximately 16 and 21 

percent, respectively. More than 50 years later, the figures 

had increased to 17 and 25 percent, respectively (Baker et 

al. 1988). 

The estimated amount of canopy coverage of ponderosa pine stands before Anglo-American settlement 

ranged from 17 to 22 percent (Covington and Sackett 1986). 

By the early 1990s, the canopy coverage had increased 

from 40 percent to more than 70 percent (Johnson 1995). 

In a recent paper, Johnson (1995) reported that ponderosa pine forests decreased by 206,000 acres from 1962 to 

1986 in New Mexico and Arizona, mainly due to logging. 

Increased density of pines during this period was attributed to partial cutting in some areas and no cutting in 

others. Effective fire suppression was a third factor in causing this density condition. 

Exotic Plants Species 

A number of exotic plant species have become established in Southwestern ponderosa pine forests following 

accidental or intentional introduction (table 5). Two introduced grasses are major understory components in the 

central and northern portions of the region. These are 

sheep fescue (Festuca ovina), a bunch grass, and Kentucky 

blue grass (Poa pratensis), a sod grass, which are both 

highly palatable to all livestock (Dick-Peddie 1993; Gay 

and Dwyer 1970). The fescue may have been introduced 

early in the colonial period, while the blue grass is a 20thcentury introduction (deBuys 1985). Hoarhound (Marrubium vulgare), another early naturalized species, is much 

less common. Yellow and white sweet-clovers (Melilotus 

albus and M. oficinalis), probably introduced by the Spanish, are found along roadways and other disturbed areas 

Table 5. Exotlc plant species In the Southwest. 

(Dick-Peddie 1993; Hermann 1966; Hitchcock 1935; 

Stefferud 1948). Mullein (Verbascum thaspus), an important medicinal plant for at least 3 centuries, has thrived in 

disturbed areas, especially in burned ponderosa pine 

stands (Scurlock 1997). 

Early in this century, the Eurasian crested wheatgrass 

(Agropyron cristatum) was introduced to National Forests 

in New Mexico and Arizona because of its forage value 

(Scurlock 1997). This species is now established across the 

Southwest. These species have diminished the cover of 

more livestock palatable, native bunch grasses and have altered understory plant composition and general ecology. 

Prehistoric and Historic Human 

Uses of and Impacts on Birds 

The uses of and impacts on raptors, game birds, and 

other non-passerines in ponderosa pine forests is poorly 

understood. Localized use of birds in forests near large 

population centers, such as Chaco Canyon, was probably 

relatively high. Intensive logging may have occurred in 

the closer stands of ponderosa pine. Spanish modifications to forest habitats in the colonial period were minimal, although growth of major settlements such as Taos, 

Santa Fe, Albuquerque, Belen, and Tucson steadily increased from 1821 to 1846. The subsequent increase of 

Anglo-American populations, combined with the Spanish and American Indian populations, adversely affected 

ponderosa pine forest habitats and associated bird species. Subsequent impacts due to urbanization and recreation after 1945 are addressed by Marzluff in Chapter 5 of 

this volume. 

Date of 

Common name Scientific name introduction Source 

Alferilio 

Hoarhound 

Crested wheatgrass 

Kentucky bluegrass 

Meadow fescue 

Sheep fescue 

Mullein 

Shepherd purse 

Sweetclover(s) 

Oxeye daisy 

Dandelion x"* 

Erodjum cicutarium 

Marrubium vulgare 

Agropymn cristaivm 

Poa pratensis 

Festuca elatior 

Festuca ovina 

Verbascum thaspus 

Capsella bursapastoris 

Melilotus alba M. officinalis 

Chrysanthemum leucanthemum 

? 

pre-l600? 

post-1935 

post-1 598 

late 19th c. 

1598? 

post-1 800? 

? 

pre-1915 

? 

Curtin 1965 

Wooton 191 5 Tierney 1983 

Hitchcock 1935 

Gay and Dwyer 1970 

Hoover et at. 1948 

deBuys 1985 

Haughton 1978 

Reed 1970 

Wooton 191 5 McKee 1948 

Reed 1970 

faraxacum officinak pre- 1 600? Reed 1 970 Tierney 1 983 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 5 1 
Chapter 3 

American Indian 

Bird Remains from Archaeological Sites 

The close relationship that American Indians in the 

Southwest have had with local bird species extends back 

more than 10,000 years and involves activities such as 

hunting, trapping, gathering eggs, raising and keeping live 

birds, and using birds or their parts in rituals. 

Birds collected by early American Indians living in or 

near ponderosa pine forests were either used or traded, 

sometimes over long distances, turning up at archaeological sites far from ponderosa pine forests. Remains of small 

passerines at Southwestern archeological sites are less 

common than large birds such as raptors. Remains of 

Mexican parrots, such as military macaw and thick-billed 

parrot, were found at excavations at Chaco Canyon in 

northwestern New Mexico, where they were probably 

used for their feathers and skins. Also uncovered at Chaco, 

were sandhill crane, several raptors, black-billed magpie, 

and common raven bones (Judd 1954; Ladd 1963; 

Schroeder 1968; Akins 1985). 

At Anasazi sites at Canyon de Chelly in northeastern 

Arizona, the bone or feather remains of 34 wild bird species have been recovered. Among these remains the 

mourning dove, northern flicker, yellow-bellied sapsucker, 

common raven, house wren, and western bluebird are 

found in ponderosa pine forests. Two varieties of domesticated turkey and a scarlet macaw have also been identified (Morris 1986). Nine of the 12 species found at Canyon de Chelly have also been recovered at Mesa Verde 

National Park and 6 of the 12 species have been found at 

Wupatki National Monument, a site in east central Arizona with ponderosa pine (Morris 1986). 

Spanish documents from the early colonial period (1540 

to 1598) for New Mexico and Arizona indicate that geese, 

cranes, American kestrel, eagles, wild and domesticated 

turkeys, macaws, parrots, quail, and black-billed magpie 

were kept in American Indian villages and used for their 

meat or feathers (Schroeder 1968). 

Birds as Spiritual Symbols 

Birds were incorporated into every aspect of American 

Indian life. They were associated with numerous natural 

elements, such as sky, earth, sun, and moon and with daily 

activities such as crop planting, hunting, racing, and war. 

Some birds were thought of as messengers between gods 

and humans, while others were connected to weather phenomenon. At Taos Pueblo, the saying, "we are in one nest" 

reflects how closely the Taos Pueblo Indians identified 

with birds (Hughes 1983). 

About 100 bird species had roles in the myths, folklore, 

rituals, and ceremonies of Pueblo Navajo, Apache, and 

other tribes (Buskirk 1986; Petit 1990; Schroeder 1968; 

Tyler 1979; Russell 1975). A majority of these 100 species 

occurred in the prehistoric and historic ponderosa pine 

forests of the Southwest, which were inhabited by various American Indian tribes through time. Among the most 

important birds to the American Indians were the golden 

and bald eagles, red-tailed hawks, owls, indigenous and 

imported parrots, macaws, wild and domestic turkeys, 

hummingbirds, ravens, pinyon jays, nuthatches, and some 

warbler species. 

Eagles and red-tailed hawks were sky-related. Owls 

were considered symbols of the dark and, among some 

Rio Ghnde Pueblos, were associated with witchcraft. Because the wild turkey was the only domestic native bird, 

both domestic and wild turkeys were believed "bound to 

the earth." Brightly colored macaws and parrots were connected to the sun and rainbow, while hummingbirds were 

"rain birds" due to their association with summer flowers and precipitation. Ravens and crows were affiliated 

with war and dark rain clouds, while pinyon jays were 

revered for their aggressive behavior, large "warrior" 

flocks, and "war cries." The red-shafted northern flicker 

was associated with war and sunrise because of its red 

wing feathers and tree "drumming." Nuthatches who 

move down tree trunks, were also affiliated with war because their movement was opposite normal behavior 

(Tyler 1979). 

Birds in Prehistoric and Historic Art 

Fetishes (small-scale likenesses of animals usually 

shaped from stone) have been made by various Southwestern American Indian tribes for over a thousand years. 

These objects were believed to bring good luck, power, or 

protection to the bearer. Eagles, owls, ducks, and ravens 

were the major bird forms produced as fetishes by American Indians in Arizona and New Mexico (McManis 1995). 

The Navajo made bird fetishes of stone and cottonwood. 

Bird forms resembling mourning dove, black-billed magpie, macaw, and an unidentified woodpecker have been 

recovered (Kluckhohn et al. 1971). 

Bird figures or feathers were sometimes painted on 

pottery; ceramic vessels in the shape of birds were less 

frequently crafted. The Anasazi fashioned pottery vessels 

into bird forms such as ducks, parrots, and turkeys 

(Peckham 1990). Bird figures were commonly used on 

pottery at Zuni, Acoma, and Zia. The late prehistoric 

Mimbres of Southwestern New Mexico painted quails, 

turkeys, parrots, cranes, herons, hummingbirds, owls, 

crows, ravens, roadrunners, swallows, or swifts on the 

inside of their pottery (Brody 1977). 

Prehistoric and historic petroglyphs (images chiseled 

into rock) and pictographs (images painted on rock) of 

birds are relatively common images produced by American Indians across the Southwest. Petroglyphs date from 

over 3,000 years old to as recent as this century, while pictographs are less common and more recently created. Bird 

figures occur in southeast Utah, southwest Colorado, and 

northeast Arizona. Petroglyphs dating from 900 A.D. to 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
A Historical Overview 

present in north, central, and southern New Mexico commonly have bird forms. The 18th-century Navajo in northwest New Mexico created pictographs and petroglyphs 

of birds (Schaafsma 1980). 

At 2 Anasazi archeological sites near Los Lunas and 

Bernalillo, New Mexico, 30 bird species have been identified on kiva wall murals including bald eagle, parrots, 

macaws, whooping and sandhill cranes, hummingbird, 

mountain bluebird, swallow, raven and/or crow, magpie, 

jay, and loggerhead shrike (Hibben 1975; Dutton 1963). 

Many of the mural species are common to ponderosa pine 

forests and other Southwestern vegetation types, but exotic or unusual species such as quetzal and pileated woodpecker are also featured. 

Birds Captured for Feathers, Pets, and Food 

The extent that trapping and hunting by early American Indians influenced the bird populations of ponderosa 

pine forests is difficult to assess without written record 

and only minimal archeological evidence. Although hunting was not considered a sport, it was practiced by some 

tribes to control population numbers. Bands or families 

of Utes were assigned territories where they monitored 

bird numbers. One section within the territory was hunted 

only as an emergency food source (Hughes 1983). Birds 

were taken with bow, traps, snares, and by hand 

(Kluckhohn et al. 1971). 

Feathers and/or skins of numerous species were used 

in rituals and ceremonies and particular species, such as 

eagles and parrots, were traded great distances. A presentation of feathers was made by the Pueblo Indians 

when planting or building. Wild turkey feathers and macaw or parrot feathers decorated Anasazi and Pueblo 

prayer sticks. Other uses of feathers by the Pueblo included robes, blankets, clothing, fetishes, ceremonial headdresses, quivers, shields, masks and basket decorations, 

and arrows (Hill 1982; Ladd 1963; Tyler 1979). 

Hill (1982) reported that the Santa Clara Pueblo used 

feathers of many ponderosa pine passerines for dance and 

hair ornaments and other ceremonial purposes. He cites 

feather use of flycatchers, Steller's jay, pinyon jay, blackbilled magpie, mountain and western bluebirds, Scott's 

and Bullock's orioles, western and hepatic tanager, and 

Grace's warbler. In a more comprehensive account, Ladd 

(1963) listed 45 bird species found in ponderosa pine forests that were important to Zuni Pueblo people (table 6). 

Most of these were used for feathers, but parrots, Steller's 

jay, American robin, and western and mountain bluebird 

were also considered pets. Turkey, mourning dove, northem flicker, Steller's jay, and common raven, were identified as food sources (table 6). 

The Navajo also used feathers from various species of 

birds (Kluckhohn et al.). The feathers of eagles, which were 

ritually hunted, and turkeys were used on arrow shafts. 

Feathers from both of these birds were used to decorate 

Table 6. Zuni Indian uses of ponderosa pine birds. 

Common name Feathers Pets Food 

Turkey 

Mourning dove 

Pam 

Great horned owl 

Common nighthawk 

White-throated swift 

Broad-tailed hummingbird 

Northern flicker 

Ws' woodpecker 

Hairy woodpecker 

Downy woodpdar 

Cassin's kingbird 

Ash-throated flycatcher 

Say's phoebe 

Violet-green swallow 

Rough-winged swallow 

Purple martin 

Steller's jay 

Black-billed magpie 

Common crow 

Common raven 

Pinyon jay 

White-bnrasted nuthatch 

Canyon wren 

Rock,m 

American robin 

Western Wwebird 

Mountain bluebird 

Townsend3 solitaire 

Loggerhead shrike 

Brewer's blackbird 

Western tanager 

Black-headed gmhk 

Lesser goldfinch 

Green-tailed tm&w 

Spotted towhee 

Lark sparrow 

Dark-eyed junco 

Source: Ladd 1963. 

baskets, hats, masks, and prayer and medicine sticks. 

Feathers or skins of hawks, crows, owls, bluebirds, warblers, blackbirds, and other small birds were used to decorate ceremonial clothing and items such as prayer sticks. 

Eagle claws were sometimes strung on necklaces. 

A number of birds were also used as food by the Apache 

and Navajo (Mayes et al. 1977). The western Apache ate 

wild turkey, quail, dove, geese, duck, some small birds, 

and various bird eggs (Buskirk 1986). Vulture feathers 

were used by the Mescalero Indians for adornment and 

ritual cermonies (Basehart 1973; Opler 1965). 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 3 

European 

Only general references to birds of ponderosa pine forests were recorded by early Spanish explorers in the late 

16th and early 17th centuries. The species noted includes 

waterfowl, wading birds, turkeys, quail, and blackbirds. 

Spanish impacts on these birds species was limited by 

seasonal hunting with bow or snares. The earliest reference to birds, specifically turkey, was made by Pedro de 

Castaneda, one of the chroniclers of Coronado's expedition (1540 to 1542). Castaneda wrote, "There are a very 

great many native fowl in these provinces, and cocks with 

great hanging chins" (Hodge 1946). In May 1583, explorer 

Antonio de Espejo, in the Verde River Valley, Arizona, referred to parrots; several historians have suggested that 

these were thick-billed parrots (Hammond and Rey 1966; 

Schroeder 1968). 

Spanish bird hunting was minimal in the colonial period; turkeys were usually acquired through trade with 

the Pueblos. Hunting of quail, partridges, and grouse is 

mentioned in documents, but was not intensive (Carroll 

and Haggard 1942). In 1766, one Spanish explorer, Nicolas 

de Lafora, commented that, "Partridges are abundant and 

are caught by hand" in New Mexico (Kinnaird 1967). 

Populations of species, such as wild turkey, prairie 

chicken, and partridges (probably quail), were larger in 

the colonial period than in more recent history, and their 

ranges were more extensive than today (Bolton 1946; 

Hodge 1956; Kinnaird 1967). 

Anglo-American settlers who arrived in the Southwest " 

in the early to mid-1800s used firearms extensively and 

hunted birds for sport. Most of these settlers, primarily 

trappers and traders, killed wild turkeys for food. Turkeys, described as abundant, were noted by United States 

Army contingents in Arizona in 1846 and 1847. In the 

1850s, travelers bound for California and boundary and 

road surveyors also noted the abundance of turkeys. Dr. 

B.J.D. Irwin observed mourning dove, "wild pigeon" (possibly band-tailed) and wild turkey while stationed at Fort 

Buchanan in southeastern Arizona (Davis 1982). 

From the 1860s to the early 1900s, commercial hunting 

was practiced by Anglo-American settlers in the Southwest. Army expeditions had hunters, as did railroad work 

crews. Miners shot or trapped birds for food for boarding 

house dining rooms, restaurants, and personal use. Although mammals were the main meat species hunted, 

geese, ducks, wild turkey, grouse, doves, quail, crows, 

ravens, robins, and blackbirds were also food sources. Bird 

eggs were intensively collected during this period. 

Women's fashions, especially feathers or skin for hats, also 

placed significant demand on bird populations. Passage 

of the Lacey Act in 1900 ended commercial hunting activity (Borland 1975). 

Early Ornithological Surveys 

The first scientific studies of birds in New Mexico and 

Arizona were conducted during the mid- to late 1800s 

(table 7). Recorded field observations, bird specimen collecting, and, less frequently, egg collecting comprised this 

work. Some of the earliest field professionals were trained 

in orniihology or a related field. Some military officers 

also collected and recorded bird field observations in Arizona and New Mexico. By the late 1800s and into this century, professional ornithologists were conducting field 

work and specimen collecting. 

Dr. Thomas Say, eminent ornithologist and entomologist, was the first trained observer and collector in New 

Mexico. In 1820, he accompanied Stephen H. Long to Colorado where the expedition split into 2 groups. Say's party 

traveled south to the headwaters of the Canadian River, 

then followed the river through northeastern New Mexico, 

eventually reaching Fort Smith, Arkansas. Among Say's 

collected specimens were the blue grouse and a flycatcher, 

later named Say's phoebe (Eifert 1962). 

Of the early United States Army observers, Lt. James 

Abert's collections and descriptions were perhaps the most 

Table 7. Ornithologists in New Mexico and Arizona, 182& 

1960s. 

Ornithologist Time period 

Thomas Say and Edwin James t820 

James Abert 1846 

George A. McCall 1850 

Samuel Woodhouse 1850-1 851 

Fullerton Spencer &M v 1 856-1 887 

Caleb Burwell Kennerly 1853 

T. Charlton Henry 1853-1 854 

Dewitt Clinton Peters 1854-1 856 

W. W. Anderson 1858 

Elliott Coues 1860,1880s 

Charles Emil Bendire 1872-1 873 

Henry Weatherbee Henshaw 1873-1 874 

Edgar Alexander Mearns 1884-1 893 

Florence Merriam Bailey late 1800s-early 1900s 

Junius Henderson & John P. Harrington 191 0-1 91 3 

Fannie Ford 191 1 

J. Stokely Ligon 1926-1 950s 

Lyndon L. Hargrave 1926-1 970s 

Gale Monson 1934-1 980s 

Allan R. Phillips 1930s-1958 

Herbert Brandt % 1930s-1940s 

Edmund Ladd 1960s 

Source: Abert 1962; Brown 1982; Eifert 1962; Henderson and Harrington 1914; 

Ligon 1961 ; Norwood 1993. 

54 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
A Historical Overview 

comprehensive. Abert recorded many mammals and 26 

species of birds along the Middle Rio Grande. Ten of these 

species were found in the montane ponderosa pine including the bald eagle, sparrow-hawk (American kestrel), 

wild turkey, red-winged flicker (northern), sapsucker 

(probably red-naped or yellow-bellied), Steller's jay, common raven, Mexican bluebird (possibly western), American robin, and loggerhead shrike (Abert 1962). 

Perhaps the earliest naturalist to collect and report on 

mammals and birds of the Southwest was Samuel 

Woodhouse, assistant surgeon, United States Army. He 

accompanied an army expedition in 1850 and 1851 that 

traveled up the Rio Grande from El Paso to Santa Fe (Ligon 1961). During this trip, Woodhouse became the first 

to observe and collect white-throated swifts, which he 

found at El Morro, New Mexico. He also collected the 

scrub jay, the black-capped vireo, and a finch (Eifert 1962). 

In 1853 and 1854, another army doctor, T. Charlton Henry, 

recorded 170 species of birds while stationed at Forts Thorn, 

Fillmore, and Webster in New Mexico. His lists include comments on range and seasonal occurrences (Ligon 1961). 

Colonel George A. McCall, who conducted an inspection of New Mexico's military posts from March to October 1850, published his observations on birds made during 

his travels around the territory (McCall 1852). He reported 

67 species and collected a few bird specimens such as a peregrine falcon taken at Santa Fe. McCall noted that the brownheaded cowbird was "not numerous" and that the common 

nighthawk was numerous in the Southwest (McCall1852). 

Army surgeon Elliott Coues collected over 200 species 

of birds in Arizona and parts of New Mexico in the 1860s 

and 1880s. Coues, while traveling with an army unit 

bound for Whipple, Arizona, collected a new species of 

warbler near Old Fort Wingate, New Mexico. This bird 

was collected in July 1864 and was later named for his 

sister Grace (Eifert 1962). He published A Key to North 

American Birds and Birds of the Colorado Valley. Coues has 

been called the "most prodigious of all American ornithologists" (Kastner 1986; Ligon 1961). 

One of Arizona's best known ornithologists of the 19th 

century was Major Charles Emil Bendire who was stationed at Forts Bowie, Lowell, and Whipple, Arizona and 

Fort Burgwyn, New Mexico from 1872 to 1873. His specialty was bird eggs, which he widely collected. His best 

known published work was Life Histories of North American Birds (1892). Bendire had several bird species named 

for him; he was also a founder of the American Ornithologists' Union (Ligon 1961). 

An early ornithologist who worked in New Mexico was 

Henry Wetherbee Henshaw who served with the U.S. 

Geographical and Geological Explorations and Surveys. 

Henshaw observed and collected birds from 1873 to 1874 

in the northern part of New Mexico and around Old Fort 

Wingate, New Mexico. He published his work in 1885 and 

1886 in issues of The Auk. (Ligon 1961). 

All of the foregoing military ornithologists worked under Fullerton Spencer Baird who was Assistant Secretary, 

then Secretary of the Smithsonian Institution from 1850 

to 1887. Baird, along with T. M. Brewer and R. Ridgway, 

produced A History of North American Birds, published in 

1874 (Eifert 1962; Ligon 1961). 

The best known woman ornithologist in the Southwest 

was Florence Merriam Bailey, who conducted field observations, collected bird specimens, and wrote several significant publications from the late 1800s through the early 

1900s. Her best known publications are the Handbook of 

Birds of the Western United States (1902) and Birds of New 

Mexico (1928). Bailey was the first female fellow of the 

American Ornithologists' Union (Behle 1990; Ligon 1961) 

and the first woman to receive the Brewster Medal for her 

publication Birds of New Mexico (Norwood 1993). 

A relatively comprehensive list of New Mexico birds 

was compiled by Fannie Ford in 1911 for the State Game 

and Fish Department. She reported 314 species and subspecies. At about the same time, the earliest major work 

on the ethno-ornithology of an American Indian tribe in 

the Southwest was conducted by Junius Henderson and 

John Peabody Harrington of the Bureau of American Ethnology, Smithsonian Institution. This field and literature 

review, made from 1910 to 1913 and published in 1914, 

focused on the relationship between the Tewa Pueblo of 

New Mexico and regional birds and other fauna (Henderson and Harrington 1914). 

J. Stokely Ligon, who with Aldo Leopold directed the 

predator control program in New Mexico, headed up a 

wild game survey in New Mexico from 1926 to 1927. Birds 

surveyed included golden eagles, which Ligon viewed as 

"a serious enemy of certain species of game" and young 

cattle, goats, and sheep. He noted that killing hawks had 

severely reduced their numbers. Ligon believed that birds 

of prey helped control the rodent population and lobbied 

for protecting legislation. Magpies were considered "enemies" of quail, pheasants, and turkeys, and Ligon recommended that federal and state wildlife personnel initiate control programs for this species (Ligon 1927). Ligon 

later published his New Mexico Birds and Where to Find 

Them, which includes historical data on 399 bird species 

in the state. Included with species descriptions are notes 

on former ranges and status of rare, endangered, or threatened species. 

Archeologist-ornithologist Lyndon L. Hargrave, who 

primarily worked in Arizona from 1926 into the 1970s, 

accumulated a comparative collection of more than 

300,000 bird bones. He conducted field work with ornithologists Alex Wetmore, the late Allan R. Phillips, and 

Herbert Brandt, and worked with numerous archeologists. 

Hargrave's best known publication is "Mexican Macaws" 

(1970). 

Phillips and Brandt began fieldwork in Arizona in the 

1930s. Phillips' M.A. thesis at the University of Arizona 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 3 

was, "The Faunal Areas of Arizona: Based on Bird Distribution" (Brown 1982). He moved to Mexico to study birds 

in 1958 and collaborated with Gale Monson on An Annotated Checklist of the Birds of Arizona (1981). Herbert Brandt 

also worked in Arizona in the middle of this century. His 

best known work is Arizona and Its Birdlife (1951). Monson 

also began his ornithological investigations in Arizona in 

the 1930s and worked for the U.S. Fish and Wildlife Service for 29 years. Monson, Phillips, and Joe Marshall collaborated on The Birds of Arizona (1964) (Monson and 

Phillips 1981). 

Edmund Ladd of Zuni Pueblo completed a thesis on 

the ethno-ornithology of his village at the University of 

New Mexico in 1963. Much of this work focused on the 

ritual use of bird feathers, especially those decorating 

prayer sticks, and includes a discussion of specific bird 

species and their historical uses. 

Historical Bird Accounts and 

Avifaunal Changes 

Abundances from Early Studies 

The composition, distribution, and populations of avian 

species in Southwestern ponderosa pine forests have 

changed over time due to climatic fluctuations, lightning 

or human-caused fires, and/or other human disturbances 

that impact birds directly or indirectly through habitat 

change (Foxx and Tiemey 1984; Hejl1994; Jehl and Johnson 

1994; Johnson 1994; Newman 1979). Human-generated, 

historical disturbances include snaring or trapping, hunting, poisoning, pesticide use, specimen-collecting, eggcollecting, logging, snag removal, grazing, mining, erecting flight obstacles, exotic species introduction, recreation, 

and urbanization (Behle 1990; Hejl 1994). The probable 

impacts of historical human use of birds and their habitats are considered in this section. 

By evaluating relative abundances (abundant, common, 

uncommon, rare, extinct) of birds reported in 3 New 

Mexico bird publications from 1911 to 1961, species whose 

abundance changed were identified (Ford 1911; Bailey 

1928; Ligon 1961). Because differences in observer style 

and locale experience is likely to have produced biases, 

results should be cautiously interpreted. We identified 32 

species whose populations in New Mexico ponderosa pine 

forests were reported as abundant or common in 1911 but 

less abundant or rare in 1961 (table 8). Species of special 

interest based on declines or management problems are 

reported in Hejl's (1994) contemporary analysis and in 

other chapters of this volume. They include the bandtailed pigeon, olive-sided flycatcher, violet-green swallow, 

mountain chickadee, golden-crowned kinglet, pygmy 

nuthatch, and chipping sparrow. Decreases could be related to habitat loss or modification through logging, fire 

exclusion, grazing, hunting, and herbicide and pesticide 

use. However, 14 species reported as rare, uncommon, or 

common in the 1911 study were potentially more abundant by 1961. Real or apparent increases of these species 

may have been due to habitat changes, range expansion, 

observer variability, or incomplete inventories during the 

late 19th to early 20th centuries. Contemporary accounts 

report general population increases for Grace's warbler 

and range expansion for red-faced warbler; 2 of the species noted in table 8 have increased in New Mexico. 

To document specific historical information on avifaunas occupying ponderosa pine forests, we listed species 

surveyed in 4 mountain ranges in New Mexico from the 

1920s to the mid-1970s (table 9). In addition, we used 

Gilman (1908), Mayes et al. (1977), and Bradfield (1974) 

to compile avifaunal lists for the Navajo Reservation in 

northeastern Arizona and the Hopi Reservation adjacent 

to the Navajo lands (table 10). Gilman (1908) recorded 

presence/absence rather than abundance. Ponderosa pine 

forests and habitat variety are more extensive on Navajo 

lands than on Hopi, which may account for the difference 

in species number listed. These tables are included in this 

chapter to mark occurrences and relative abundances of 

bird species in time as a ready historical summary for future investigators of Southwestern ponderosa pine 

avifaunas. 

Changes in Species Ranges 

One avian species (thick-billed parrot) and a subspecies (Merrian's turkey) found in the ponderosa pine forest were extirpated historically but have been reintroduced, one unsuccessfully and the other successfully. The 

thick-billed parrot, which may have ranged as far north 

as the Verde River Basin in central Arizona in the early 

colonial period, was exterminated in the 20th century. This 

specie$ sporadically visited the Animas and Peloncillo 

Mountains in New Mexico as recently as the early part of 

this century; it was last seen in 1938 in the Chiricahua 

Mountains of southeastern Arizona (Ligon 1961; Monson 

and Phillips 1981). A small number of these parrots were 

released into the Chiricahuas in 1986 by the U.S. Fish and 

Wildlife Service, but they have not been seen since the 

1989 to 1990 drought (Snyder et al. 1995). Merriam's turkey was historically widespread in riparian woodlands 

and montane conifer forests in New Mexico and Arizona, 

but was locally extirpated between 1900 and 1920. Since 

1920, reintroduction by game and fish departments in both 

states has restored viable populations of this subspecies 

(Ligon 1961; Monson and Phillips 1981). 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
A Historical Overview 

Table 8. Recorded abundances of ponderosa pine avifauna in New Mexico. A = abundant; C = common; U = uncommon; 

R = rare; E = extinct. 

Common name 

Population 

Source Increase (I) 

Decrease (D) 

Ford 191 1 Bailey 1928 Ligon 1961 Stable (S) 

Blue grouse C D 

Merriam's turkey C D 

Band-tailed pigeon C D 

Mourning dove A S 

Thick-billed parrot a D 

Greater roadrunner a U I 

Common nighthawk C C S 

Poor-will U I 

Common poor-will U I 

Whip-poor-will U S 

White-throated swift C S 

Calliope hummingbir C D 

Broad-tailed hummin C S 

Rufous hummingbird C C C to A I 

Lewis' woodpecker LC Locally U to C S 

Acorn woodpecker C S 

Williamson's sapsucker C U to C U D 

Yellow-bellied sapsucker S 

Downy woodpecker S 

Hairy woodpecker S 

Three-toed woodpecker S 

Northern flicker 

Olive-sided flycatcher 

Western wood pewee 

Dusky flycatcher S 

Say's phoebe S 

Cordilleran (western) flycatcher J to C I 

Ash-throated flycatcher S 

Cassin's kingbird C J D 

Purple martin 

Tree swallow 

Violet-green swallow 

Black-billed magpie 

Steller's jay 

Pinyon jay 

Gray jay 

Clark's nutcra Locally R 1 U D 

American croi U to A 

Common rave 

Black-capped chickadee 

Mountain chickadee 

Golden-crowned kinglet 

Ruby-crowned kinglet 

Red-breasted nuthatch 

White-breasted nuthatch 

Pygmy nuthatch 

Brown creeper 

Winter wren a 

Rock wren S 

Canyon wren Locally C R Locally C S 

continued on next page 

USDA Forest Service Gen.Tech. Rep. RM-GTR-292. 1997 
Chapter 3 

Table 8. (continued) 

Population 

Source Increase (I) 

Decrease (D) 

Common name Ford 191 1 Bailey 1928 Ligon 1961 Stable (S) 

Mountain bluebi 

Townsend's warble 

Brewer's blackbir 

Lincoln's sparrow C U U D 

a Data not recorded. 

58 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
A Historical Overview 

Table 9. Recorded ponderosa pine avifauna occurrence in 4 New Mexico mountain ranges. 

La Mesa 

Sangre de 

Crlsto Mtns Sandla Mtns Jemez Mtns Guadalupe Mtns 

1 920-1 950s" 19208-1 950sb Common name pre-1 977c 1972-1 974d 

Merriam's turkey 

Wild turkey 

E 

n 

c 

3and-tailed pigeon X . X 

Aourning dove X X 

hater roadrunner 

Common nighthawk X X X X 

Poor-will 

Whip-poor-will 

White-throated swifi 

Calliope hummingbi 

Broad-tailed hummi 

Rufous humminabird 

Black-chinnt 

Blue-throate 

Lewis' wood 

Acorn woodpec~er 

Williamson's sapsucker 

Yellow-bellied sapsucker 

Downy woodpecker 

I rd 

ngbird 

sd h;;mmingbird X 

sd hummingbird X 

peeker . , . , . , . . 

Hairy woodpecker 

Three-toed woodpecker 

Ash-throated flycatcher 

Wright's flycatcher 

Hammond's flycatcher 

Cassin's kin1 gbird X 

Purple marti 

Violet-green 

Black-billed magple 

n 

swallow 

Steller's jay 

Pinyon jay 

Gray jay 

Clark's nutcracker 

Mountain c 

Bushtit 

Red-breasted nuthatch 

White-breasted nuthatch 

continued on next page 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 59 
Chapter 3 

Table 9. (continued) 

La Mesa 

Sangre de 

Cristo Mtns Sandia Mtns Jemez Mtns Guadalupe Mtns 

Common name 1920-1 950s' 1920s-1 950sb pre-1977= 1972-1 974d 

Canyon wren X X X 

. . 

Townsend's solitaire X X X 

Swainson's thrush X 

American robin X X X X 

Townsend's warbler X X 

American goldfinch X 

Evening grosb 

Baird's sparrow X 

Vesper sparrow X 

Sava 

Song 

Source: 

a Ligon 1961 

Schwarz 1995 

Foxx 8Tierney 1984 

Newman 1979 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
A Historical Overview 

Table 10. Ponderosa pine avifauna on Navajo and Hopi reservations. A = abundant; C = common; U = uncommon; R = rare; 

S = sparse; E = extinct; X = abundance not given in paper. 

Common Name Gilman 1908a 

- -- 

Mayes et al. 1 977b Bradfield 1974= 

Merriam's turkey 

Mourning dove 

Common nighthawk 

Whip-poor-will 

White-throated swift 

Broad-tailed hummingbird 

Rufous hummingbird 

Lewis' woodpecker 

Acorn woodpecker 

Williamson's sapsucker 

Yellow-bellied sapsucker 

Downy woodpecker 

Hairy woodpecker 

Northern flicker 

Olive-sided flycatc 

Cassin's kingbird 

Western wood pewee 

Cordilleran (weste 

Say's phoebe 

Ash-throated flycatcher 

Purple martin 

Violet-green swallow 

Black-billed magpie 

Steller's jay 

Pinyon jay 

Clark's nutcracker 

Common raven 

Mountain chickadee 

Red-breasted nuthatch 

White-breasted nuthatc 

Pygmy nuthatch 

Brown creeper 

Rock wren 

Canyon wren 

House wren 

Western bluebird 

Mountain bluebird 

Townsend's solitaire 

Hermit thrush 

American robin 

Golden-crowned 

Black-throated 

Virginia's warbler 

Townsend's warbler 

Grace's warbler 

MacGillivray's warbler 

Western tanager 

Black-headed grosbe 

Spotted towhee 

USDA Forest Service Gen.Tech. Rep. RM-GTR-292. 1997 

continued on next page 

6 1 
Chapter 3 

Table 10. (continued) 

Common Name Giiman 1908a Mayes et al. 1977b Bradfield 1974= 

ailed towhee 

sparrow 

,arrow 

unco 

ickbird 

ill 

Green4 

Vesper ! 

Song sl: 

Chipping sparrow 

Dark-eyed j 

Brewer's bl~ 

Red crossbi 

Cassin's finch 

Pine siskin 

Lesser goldfinch 

Year of record: 

a 1907. 

1958-1 976. 

pre-1974. 

Source: Bradfield 1974. 

Several Southwestern species associated with ponderosa pine have moved north in the last 40 years or so (Jehl 

and Johnson 1994; Johnson 1994). These include the whippoor-will, which now ranges across much of Arizona into 

southwest Utah and over most of New Mexico into south 

central Colorado, and the red-faced warbler, which is now 

found over all but northern and eastern New Mexico and 

northwestern and northeastern Arizona. The summer 

tanager occupies portions of north central and west central Arizona and New Mexico. The white-winged crossbill has moved southward into the Rocky Mountains of 

southern Colorado and northern New Mexico where it 

bred in the late 1970s and 1980s. Two explanations for this 

phenomenon are: 1) climatic trends with moister and 

warmer summers since 1965; and 2) reoccupation of 

former range Uehl and Johnson 1994; Johnson 1994). 

Conclusion 

Of the various human activities that have impacted forest composition and structure, logging and fire suppression had the greatest influence on ponderosa pine forest 

ecosystems since European settlement. Every accessible 

ponderosa pine forest in New Mexico and Arizona was 

heavily logged from the 1870s to the 1930s (Baker et al. 

1988; Houk 1993). Demand for timber was primarily generated by railroad and mine operations. The effects of logging on southwestern birds were unknown before European settlement; therefore, it is difficult to document 

alterations of bird populations caused by early American 

Indian use of ponderosa pine. 

Hejl (?994), when reviewing human-induced changes 

that occurred over the last 100 years in birds inhabiting 

Western coniferous forests, proposed that logging, fire 

exclusion, snag removal, loss of herbaceous understory, 

and/or increased densities of small trees resulted in population declines in bird species associated with burns, oldgrowth forests, open forests, or snags. Canopy and bark 

foragers, which historically dominated ponderosa pine 

forests, were impacted the most. According to Hejl, species exhibiting historical declines include broad-tailed 

hummingbird, acorn woodpecker, violet-green swallow, 

purple martin, mountain chickadee, white-breasted 

nuthatch, pygmy nuthatch, brown creeper, western bluebird, mountain bluebird, American robin, red-faced warbler, lark sparrow, and chipping sparrow. 

DeSante and George (1994) identified 9 avian species 

whose breeding populations in ponderosa pine forests 

have decreased in Arizona (AZ) or New Mexico (NM) over 

the last 100 years. These are blue grouse (AZ, NM), wild 

turkey (AZ, NM), spotted owl (AZ), lesser nighthawk 

(NM), white-throated swift (AZ), purple martin (AZ), 

western bluebird (AZ), Lucy's warbler (AZ), and song 

sparrow (AZ). Since 1890, wild turkey and evening grosbeak have experienced range reductions. 

In contrast to those species with historical declines, 10 

species (American crow, cordilleran flycatcher, house 

wren, Townsend's solitaire, hermit thrush, solitary vireo, 

Virginia's warbler, yellow-rumped warbler, Grace's warbler, and western tanager) have apparently increased in 

numbers in the Western United States (DeSante and 

George 1994; Hejl1994). The downy woodpecker, blackcapped chickadee, red-faced warbler, and brown-headed 

cowbird have increased their breeding distribution. These 

changes are believed to be caused by climatic shifts, landUSDA Forest Service Gen.Tech. Rep. RM-GTR-292. 1997 
A Historical Overview 

scape modification, grazing, and/or vegetative shifts 

(Brown and Davis 1995). 

Research Needs 

Systematic searches of published and unpublished archeological and historic reports that contain data on ponderosa pine avifauna use by prehistoric and historic 

American Indians is needed. This information would provide a data base for determining: 1) species range; 2) use 

of native and exotic bird species for food, tools, personal 

adornment, ritual, pets, etc.; and 3) impacts on populations from existing and future fire history studies. 

Little research on the pre-1900 relationship between 

European settlers and Southwestern ponderosa pine forest birds has been conducted. Various published and unpublished reports, papers, and other documents need to 

be searched, and pertinent data extracted and synthesized. 

Careful scrutiny of climatic records, and logging, ranching, farming, and other recorded activities would produce 

useful information on impacts and population changes. 

As a baseline for determining these phenomena, early 

(1850 to 1940) published and unpublished field notes and 

lists recorded by ornithologists in the Southwest should 

be examined for seasonal occurrence and population size 

of species associated with ponderosa pine forests. These 

data might indicate impacts on avian populations near historic villages and towns or those species obtained from farther distances. 

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USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 4 

Songbird Status and Roles 

Linnea S. Hall, Michael L. Morrison, and William M. Block 

Introduction 

This chapter reviews studies on songbird ecology conducted in Arizona, New Mexico, and Colorado; studies 

from outside this region are mentioned when they bear 

direct relevance to our primary region. The studies were 

conducted in sites where ponderosa pine occurred at least 

in equal coverage with other trees. We also include studies conducted in pine-oak (pine predominant) or oak-pine 

(oak predominant) woodlands of southeastern Arizona 

and Southwestern New Mexico. Our review begins with 

population studies, including research on distribution, 

abundance, and trends in population numbers. We then 

discuss the various roles of birds in the ponderosa pine 

forest. Next we cover the multifaceted topic of avian natural history and habitat preferences, including use of vegetation and special habitat features, nest predation, foraging habits, and migration habits. We also review the 

prioritization systems for identifying species of special 

research and management concern. 

Population Status 

Research Limitations 

Long-term data sets such as Breeding Bird Surveys 

(Robbins et al. 1986; Pete john et al. 1995) and Christmas 

Bird Counts (Bock and Root 1981) usually allow for indices of relative abundance. Results of many research studies compare absolute or relative abundance of birds among 

different impacts (such as logging and fire) or conditions 

(such as varying tree density and season). But few data 

exist to estimate population parameters such as survival 

and reproduction. Few data are available to examine 

nonbreeding or migrating populations because most of 

the data are collected during the breeding season. Trend 

data are limited to Breeding Bird Surveys (BBS) and Christmas Bird Counts (CBC); we found no relevant Breeding 

Bird Census trend data (Marshall 1991). Breeding Bird 

Atlas data for the Southwest are too recent (collecting started 

in 1994) to provide trend information (T. Corman, Arizona 

Dept. of Game and Fish, personal communication). 

Therefore, we review here the information on populations by summarizing relevant research results and by 

summarizing BBS data to examine population trends. Rigorous comparisons of population estimates from different research projects are difficult because of different data 

collection methods, different sampling intensities, different skill levels of observers, and different analytic techniques. Also, methods used to sample avian populations 

have inherent biases (compare Verner 1985, for a review 

of avian census methods). Thus, we limit our discussion 

of research results to brief descriptions of major studies 

and to generalizations based on the collective results of 

these studies. 

Research Results 

Szaro and Balda (1979) measured breeding bird populations within the Beaver Creek watershed of the Coconino 

National Forest, Arizona. Vegetation within their study 

area was dominated by ponderosa pine with Gambel oak 

and alligator juniper in the understory. They used spot 

mapping to index densities of individual species and selected guilds (as defined by Root 1967:335) on five plots 

representing different intensities of logging, from clearcut 

to control (that is, no logging). As might be expected, bird 

densities varied among plots and among years. Whether 

the variations in numbers represented effects of different 

cutting regimes, however, is difficult to assess; inferences 

about cause-effect relationships of logging will be covered 

in the following chapters and we will not duplicate that 

material here. However, bird populations were generally 

greatest on the "strip cut" and "silviculturally cut" plots 

and lowest on the clearcut plots; densities of birds on the 

control (unlogged) plot were intermediate to these extremes (table 1). Spotted towhees and rock wrens were 

the most abundant species on the clearcut plot; dark-eyed 

junco, Steller's jay, and white-breasted nuthatch were most 

abundant on the "severely thinned" plot; Grace's warbler, 

solitary vireo, dark-eyed junco, and chipping sparrow on 

the strip cut plot; dark-eyed junco, pygmy nuthatch, and 

Grace's warbler on the silviculturally cut plot; and whitebreasted nuthatch, pygmy nuthatch, dark-eyed junco, and 

Grace's warbler on the control plot. 

Siege1 (1989) examined habitats and populations of 

breeding birds in old-growth ponderosa pine forests on 

the Kaibab Plateau, Arizona. He compared bird numbers 

among stands representing different densities of trees: 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 4 

Table 1. Comparison of population estimates in ponderosa pine forests. See text for details of each study. Numbers provided 

are ranges of population estimates from study sites sampled in each study. 

Species 

Blakee Haldeman et al! 

Szaro & Horton & 

Baldaa Siegelb OverturfC Mannand Fall Winter Spring Spring Winter 

Br-tailed hurnrni 

0.0-0.8 9 

Common raven 0.0-1 .O 

0.0-0.: 

Mountain chickad 

Plain titmouse 

Red-breasted nuthatc 

Pygmy nuthatch 

Brown creeper 

House wren 

Ruby-crowned kinglet 

Loggerhead shrike 

American robin 

Townsend's soli 

Hermit thrush 

Western bluebir 

Cedar waxwing 

Solitary vireo 1.5-12.0 9.1-18.1 0.0-0.7 

Yellow-rumped war 3.0-1 5.0 23.447.0 0.0-1 3.0 0.2-2.8 0.0-1.6 8 

Townsend's warbler 0.0-1.8 

Red-faced warbl 

Grace's warbler 3.8-19.5 29.7-50.2 0.0-7.0 

Virginia warbler 

Brown-headed cowbird 0.4-0.8 0.0-7.0 

continued 011 next page 

USDA Forest Service Gen.Tech. Rep. RM-GTR-292. 1997 
Songbird Status and Roles 

Table I. (continued) 

Species 

Blakee Haldeman et al! 

Szaro & Horton 81 

Baldaa Siegelb OverturfC Mannand Fall Winter Spring Spring Winter 

Hepatic tanager 0.0-3.0 0.0-0.2 

Chi~~ina .. - sparrow . 1.5-1 2.0 0.6-4.3 0.0-29.0 0.0-0.2 0.0-8.8 

Spotted towhee 5.5-7.3 0.0-0.2 0.0-3.6 

Evenina arosbeak 0.2 

a Szaro and Balda (1 979); units are number of pair140 ha. 

Siegel (1989); units are number of birds140 ha. 

Overturf (1 979); units are number of pair140 ha. 

Horton and Mannan (1 988); units are number of birds140 ha. 

Blake (1982); units represent an index of occurrence based on numbers and distribution of a species with a sampling site. 

~aldeman et al. 1973: 

open, medium, and dense. Species richness showed little 

difference among stands, although dense stands had more 

individuals, particularly warbling vireos, violet-green 

swallows, western wood pewees, and Williamson's sapsuckers. He also found that Grace's warbler, yellowrumped warbler, and dark-eyed junco were the three most 

abundant species in all stands, collectively accounting for 

>40 percent of all birds detected. 

Overturf (1979) indexed populations using a spot mapping method to examine the effects of fire on ponderosa 

pine birds in northern Arizona. Populations were sampled 

from three to nine years post fire, with the exception of 

one control area where fire had not occurred recently (table 

1). The control area was the Gus Pearson Natural Area, 

Ft. Valley Experimental Forest. Generally, burned areas 

supported fewer numbers of birds and fewer species than 

the unburned area. Species found on the control but not 

found on the burned areas included violet-green swallow, 

mountain chickadee, hermit thrush, yellow-rumped warbler, Grace's warbler, and pine siskin. Burned areas, however, tended to have more species that nested or foraged 

on the ground than were found on the control site. Species that appeared to exhibit positive numerical responses 

to fire included the chipping sparrow, lark sparrow, darkeyed junco, green-tailed towhee, western bluebird, northem flicker, and house wren. Overturf attributed this difference to burned sites possessing a more well developed 

herbaceous understory than that in the control plot. 

In one of the few studies to examine populations of 

nonbreeding birds, Blake (1982) found pronounced seasonal differences between fall, winter, and spring in bird 

species composition and bird abundances in ponderosa 

pine forests of the Prescott National Forest, Arizona (table 

1). He also noted spatial differences that corresponded to 

differences in fire and logging histories. Generally, burned 

areas contained more individuals, but they were distributed among fewer species than unburned sites. Species 

restricted to burned areas included common poorwill, 

western wood-pewee, scrub jay, house wren, hermit 

thrush, and lesser goldfinch during the fall; and Cassin's 

kingbird, rock wren, American robin, solitary vireo, 

Grace's warbler, hepatic tanager, and black-headed grosbeak during the spring. Species restricted to unburned 

areas included band-tailed pigeon, acorn woodpecker, 

Lewis' woodpecker, Steller's jay, pygmy nuthatch, canyon wren, American robin, ruby-crowned kinglet, blackthroated gray warbler, spotted towhee, chipping sparrow, 

and fox sparrow during the fall; yellow-bellied sapsucker, 

Lewis' woodpecker, Steller's jay, plain titmouse, pygmy 

nuthatch, ruby-crowned kinglet, and cedar waxwing during the winter; and band-tailed pigeon, acorn woodpecker, 

ash-throated flycatcher, Steller's jay, pygmy nuthatch, 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 4 

brown creeper, Bewick's wren, ruby-crowned kinglet, loggerhead shrike, Virginia's warbler, black-throated gray 

warbler, Townsend's warbler, and spotted towhee during 

the spring. 

Haldeman et al. (1973) reported breeding season and 

wintering populations of birds from a ponderosa pine forest northwest of Flagstaff, Arizona (table 1). Their single 

study area was the 13-ha Gus Pearson Natural Area that 

they characterized as undisturbed. They recorded 18 species during winter counts and 69 species during breeding 

counts. Because they used different methods to calculate 

relative abundance for each season, comparisons between 

seasons are difficult. However, of the resident species (that 

is, those present year round), the pygmy nuthatch was 

the most common species during both seasons. Other common wintering birds were the mountain chickadee, whitebreasted nuthatch, western bluebird, and dark-eyed junco. 

Besides the pygmy nuthatch, other common breeding 

birds included the violet-green swallow, dark-eyed junco, 

mountain chickadee, American robin, and western bluebird. 

Horton and Mannan (1988) sampled populations of cavity-nesting birds in the Santa Catalina Mountains, southeastern Arizona, as part of a study to evaluate the effects 

of prescribed fire. The violet-green swallow and northern 

flicker exhibited population declines following the fire, 

whereas the mountain chickadee population appeared to 

increase. Horton and Mannan (1988) speculated that the 

population shifts were possibly attributable to changes in 

prey abundance and shifts in habitat use following fire. 

Bennetts (1991) investigated the relationship of breeding birds and dwarf mistletoe in Colorado ponderosa pine 

forests. He found positive correlations between mistletoe 

and total bird abundance and number of species, as well 

as with abundances of eight foraging guilds. He also found 

strong positive correlations of mistletoe with snag numbers and the abundance of cavity nesting birds. 

General Comparisons Among Studies 

As noted previously, differences in how studies were 

conducted preclude rigorous comparisons. However, 

some generalizations are possible. Species richness (number of species) during the breeding season ranged from 

23 (Haldeman et al. 1973) to 47 (Siegel 1989). Fewer species were detected during winter (14 to 16, Blake 1982 and 

Haldeman et al. 1973) or fall (27, Blake 1982) than during 

the breeding season. The range in species richness during 

the breeding season could have resulted from temporal 

or geographic differences, or variations in methodologies 

or skill levels of observers. 

Across the studies, there was a mixture of responses to 

heavy alteration of forest vegetation. In regard to fire, 

abundances of birds either increased (Blake 1982) or decreased (Overturf 1979), whereas species composition was 

lower on burned sites in both studies. In clearcuts studied by Szaro and Balda (1979)) bird numbers decreased, 

but in open stands studied by Siegel (1989), species 

richnesses were similar among open and "closed" stands. 

These differences indicate that treatments can elicit variable responses from bird species, probably because of 

variations in geographic location, and because of the historic (prior) conditions of the areas. 

Population Trends 

BBS data provide one of only a few sources of longterm population data from which trends may be inferred. 

However, without going into details here, it must be noted 

that many problems have been identified with BBS data 

and analyses (Peterjohn et al. 1995, Thomas and Martin 

1996). These problems include observer bias and biases 

associated with sampling design. Furthermore, a lot of 

discussion has been devoted to identifying the correct way 

to analyze BBS data (Thomas and Martin 1996). 

Regardless of these potential limitations, Miller (1992) 

evaluated population trends of ponderosa pine birds using BBS data. BBS routes were selected from Colorado (n 

= 5), Utah (n = 5), Arizona (n = 5), and New Mexico (n = 6) 

that sampled managed ponderosa pine forests. Whether 

or not these managed pine forests were a representative 

sample of pine forest of the southwest is unknown, but 

population trends in unmanaged pine forests (for example, 

old-growth forest, wilderness lands) may have differed 

from those in managed forests. To ensure that standardized methods were used, analyses were done by the U.S. 

Fish and Wildlife Service, Patuxent Research Center. 

Miller examined trends of individual species and groups 

of species as defined by nesting strategy (for example, 

primary-cavity, secondary-cavity, or cup nesters), nesting 

habitat (woodland or coniferous forest), or residency status (resident, short-distant migrant, neotropical migrant). 

Analyses were done at the state level for New Mexico (because this was the only state with adequate samples); New 

Mexico and Arizona combined; Colorado and Utah combined; and all four states combined. For New Mexico, 

Miller found declining populations of 77 percent of all 

birds examined (46 of 61), and from 50 to 100 percent of 

the species within any of the groups that he evaluated 

(table 2). Fewer population declines were noted when census routes from states were pooled (table 2). Of particular 

interest was that about two-thirds (50) of the species found 

in New Mexico and Arizona (75 total bird species) exhibited significant population declines (table 2), and many 

of these were birds that nested in open cups and species 

that tended to be year-round residents. Miller identified 

50 species that exhibited declines and 25 that exhibited 

population increases (table 3). 

The Christmas Bird Count program, sponsored by the 

National Audubon Society, provides information on the 

abundance of birds wintering in various locations in North 

America. There are, however, only two count locations 

72 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Songbird Status and Roles 

Table 2. Proportion of bird species declining 1968 to 1990 along managed ponderosa pine breeding bird survey routes, for 

species with 25 routes counted, and an average of 20.5 birds per route (modified from Miller 1992). 

New Mexico & Colorado & All four 

Guild New Mexico Arizona Utah states 

Woodland nesting 

Coniferous nesting 

Primary cavity nesting 

Secondary cavity nesting 

Open cup nesting 

Permanent resident 

Short distance migrant 

Neotropical migrant 

All birds 

that have been regularly surveyed in Southwestern ponderosa pine forest: one centered near Flagstaff, Arizona, 

which has been surveyed since 1968, and another centered 

near Mormon Lake, Arizona, which has been surveyed 

since 1982. CBC data have been shown to produce reliable indications of trends in bird abundance when a count 

has been conducted for a sufficient period of time (that is, 

about 20 years), and when a sufficient count effort has 

been expended each year (Bock and Root 1981). Although 

the Flagstaff count meets these requirements, trend analyses should not be based on only one or a few counting 

locations (Bock and Root 1981). Therefore, we have not 

included analyses of CBC data in this report. 

Several authors have recently documented range and 

population shifts for particular Southwestern bird species. 

For example, Johnson (1994) suggested northward expansion of the ranges of Grace's warbler, painted redstart, 

hepatic tanager, and summer tanager in response to "natural" climate change over the past century. Based on an 

extensive literature review, DeSante and George (1994) 

concluded that willow flycatcher, buff-breasted flycatcher, 

western bluebird, Bell's vireo, summer tanager, and song 

sparrow populations were decreasing across the west, 

whereas berryline hummingbird, violet-crowned hummingbird, black phoebe, European starling, red-faced 

warbler, and brown-headed cowbird populations were 

increasing. Whether or not these range shifts and population trends apply to Southwestern ponderosa pine forest 

is unclear, however, because the western region reviewed 

by DeSante and George encompasses many different vegetation types. 

Brawn and Balda (1988a) reviewed the population status of Southwestern ponderosa pine birds and suggested 

that broad-tailed hummingbird, acorn woodpecker, threetoed woodpecker, purple martin, violet-green swallow, 

mountain chickadee, white-breasted nuthatch, pygmy 

nuthatch, brown creeper, western bluebird, mountain 

bluebird, American robin, red-faced warbler, chipping 

sparrow, and lark sparrow populations would also be 

likely to decline over time in response to past and present 

land-use activities. Many of these species are ones that 

nest in cavities or rely on a well-developed herbaceous 

understory. We can presume that the synergistic and cumulative effects of natural vegetation change, livestock 

grazing, logging, fuelwood harvest, and fire suppression 

will underlie many of the predicted population declines 

(discussed in detail in Finch et al., this volume). 

Carothers et al. (1973a) briefly summarized the status 

of selected species in northern Arizona. They noted that 

the Lewis' woodpecker had become a fairly common permanent resident, and the evening grosbeak a locally common permanent resident in ponderosa pine forest around 

Flagstaff. In contrast, they noted a decline in numbers of 

red-breasted nuthatches in ponderosa pine. They also 

noted that the exotic European starling had changed in 

status from a rare winter visitor or transient to a common 

winter resident and an uncommon summer resident in 

the Flagstaff area. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 4 

Table 3. Increasing and decreasing bird species on managed 

ponderosa pine Breeding Bird Survey routes in Arizona and 

New Mexico, for species with 2?J routes and 20.5 birds per 

route (modifled from Miller 1992). These lists include both 

songbirds and non-songbirds. 

Decreasing Increasing 

Mallard 

Killdeer 

Band-tailed pigeon 

Mourning dove 

Hairy woodpecker 

Acorn woodpecker 

Common nighthawk 

Broad-tailed hummingbird 

Western Kingbird 

Ash-throated flycatcher 

Say's phoebe 

Western wood-pewee 

Gray flycatcher 

Horned lark 

Western scrub jay 

Common raven 

American crow 

Clark's nutcracker 

Pinyon jay 

Red-winged blackbird 

Eastern meadowlark 

Western meadowlark 

Brewer's blackbird 

House finch 

Red crossbill 

Lesser goldfinch 

Pine siskin 

Lark sparrow 

Chipping sparrow 

Canyon towhee 

Black-headed grosbeak 

Cliff swallow 

Violet-green swallow 

Loggerhead shrike 

Warbling vireo 

Solitary vireo 

Virginia's warbler 

Yellow-rumped warbler 

Grace's warbler 

Black-throated gray warbler 

House sparrow 

Northern mockingbird 

Rock wren 

White-breasted nuthatch 

Pygmy nuthatch 

Plain titmouse 

Mountain chickadee 

Common bushtit 

Ruby-crowned kinglet 

Mountain bluebird 

Turkey vulture 

Red-tailed hawk 

American kestrel 

Northern flicker 

Cassin's kingbird 

Cordilleran flycatcher 

Steller's jay 

European starling 

Brown-headed cowbird 

Vesper sparrow 

Spotted towhee 

Green-tailed towhee 

Blue grosbeak 

Western tanager 

Hepatic tanager 

Purple martin 

Barn swallow 

Rough-winged swallow 

Bewick's wren 

House wren 

Red-breasted nuthatch 

Townsend's solitaire 

Hermit thrush 

American robin 

Western bluebird 

Ecological Roles 

Seed Dissemination 

Mistletoe 

Hudler et al. (1979) studied the role of birds in the spread 

of dwarf mistletoe (Arceuthobium spp.) in a Colorado ponderosa pine forest. Long-distance seed transmission (that 

is, farther than possible by normal seed discharge) occurred infrequently; successful infection occurred once 

every four years on average. Mountain chickadees and 

pygmy nuthatches were the primary vectors of the parasite. Laboratory studies showed that seeds seldom remained viable when ingested by birds. Rather, successful 

movement of the seeds occurred when they became attached to bird feathers and later transferred to foliage. 

Bennetts (1991) and Bennetts and Hawksworth (1991) 

studied the indirect effects of dwarf mistletoe on birds in 

a Colorado ponderosa pine forest. The total number of 

birds and the total number of bird species detected increased with increasing levels of mistletoe infestation; this 

pattern was consistent across most foraging assemblages 

of birds. In addition, the number of snags and the abundance of cavity-nesting birds increased with increasing 

levels of mistletoe. The authors suggested that dwarf 

mistletoe should not be viewed solely as a forest pest (because of its often negative influence on commercial timber volume), but rather in the context of an ecological disturbance process and its influence on wildlife communities. 

That is, mistletoe is a disturbance process that changes 

the structure and function of ponderosa pine and other 

host communities. In their review of the literature, they 

also found that the witches' brooms caused by the mistletoe are an important nesting and roosting substrate for 

many species of birds and squirrels, and that some species use mistletoe as a food source. Mistletoe has been 

shown to serve as a nesting substrate by Forsman et al. 

(1984), Bull and Henjum (1990), Bull et al. (1989); as a roosting substrate by Martinka (1972); and as a food source for 

birds and other animals by Taylor (1935), Broadbooks 

(1958), Urness (1969), Farentinos (1972), Craighead et al. 

(1973), Currie et al. (1977), Ha11 (1981), and Severson (1986). 

Pine Seeds 

Balda and his coworkers (for example, Balda and 

Bateman 1971; Balda 1973, Bateman and Balda 1973) conducted a long-term, intensive study of the ecology and 

behavior of the pinyon jay in a northern Arizona ponderosa pine forest. Pinyon jays are year-round residents and 

obtain part of their winter food from pine seeds that they 

cached during the fall. This caching behavior helps spread 

pine seeds and thus plays a major role in the population 

dynamics of these trees. Clark's nutcrackers are also a 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Songbird Status and Roles 

seed-predator and a very important seed-disperser for 

wingless seeds (for example, Pinus edulis) (Tomback and 

Linhart 1990). Nutcrackers have been found to affect forest regeneration and to possibly extend the range of pinyon pines (reviewed in Christensen et al. 1991). They also 

forage on ponderosa pine seeds, when they are available, 

and may therefore play a part in the dynamics of ponderosa pine forests. Another ponderosa pine seed-predator 

is the red crossbill. The crossbill is nomadic, following 

sporadic, scattered pine seed crops (Gill 1995:290). In the 

Rocky Mountains, crossbills will nest in January and February if pine seeds are abundant (Gill 1995:275). 

Indicators of Forest Conditions 

Szaro and Balda (1982) discussed the selection and subsequent monitoring of birds as indicators of environmental change, using their data from a ponderosa pine forest 

of northern Arizona as an example. They noted that many 

different definitions have been applied to the term "indicator" for use in environmental management, including: 

1) endangered and threatened plants and animals; 2) species commonly hunted, fished, or trapped; 3) species with 

specialized habitat needs; and 4) plants or animals selected 

because changes in their populations are thought to indicate the effects of natural- or human-induced changes on 

the collective species of a major biological community. The 

use of birds as indicators is controversial (for example, 

see Morrison et al. 1992), primarily because indicator species may be affected differently from other species by habitat changes. Nevertheless, the concept is important here 

because there are diverse opinions on the subject, and 

because in certain situations (for example, chemically 

polluted environments) birds can indicate habitat conditions (Morrison 1986). 

Szaro and Balda (1982) found that species such as the 

hermit thrush, red-faced warbler, Cordilleran flycatcher, 

and pygmy nuthatch, which are found in old-growth ponderosa pine forest and only lightly disturbed areas, are 

replaced in moderately to heavily cut areas by species such 

as the western wood-pewee, yellow-rumped warbler, and 

rock wren. Therefore, those species that are most sensitive to habitat perturbations may potentially make the best 

indicator species. Some species that are too rare to be useful as indicators of the general community-such as 

Virginia's warbler, brown creeper, and hepatic tanagermay be useful indicators of special habitat needs because 

they breed in ponderosa pine. Szaro and Balda concluded 

that the two species that best indicated the overall "health" 

of the bird community were the pygmy nuthatch and violet-green swallow. They based this finding on the fact that, 

when they found high densities of pygmy nuthatches and 

violet-green swallows, they also found high densities of 

most of the other ponderosa pine forest bird species (see 

Szaro and Balda 1982, table 1). 

"Habitat specialists" as indicator species are discussed 

in Rich and Mehlhop (this volume). 

Roost and Nest Cavity Formation 

Scott (1978) summarized the frequent use of cavities in 

dead or partially dead trees in ponderosa pine forest and 

mixed pine woodlands in Arizona and New Mexico by 

the American kestrel, 7 species of owls, the elegant trogon, 

11 species of woodpeckers, 2 flycatchers, 3 swallows, 5 

chickadees and titmice, 3 nuthatches, the brown creeper, 

4 wrens, and 3 bluebirds. Similarly, Ffolliott (1983) summarized the scant literature on cavity-nesting animals in 

Southwestern ponderosa pine forests and found that at 

least 49 species of birds, 10 species of mammals, and numerous species of insects and herpetofauna used tree cavities in these forests. In addition, he noted that 63 percent 

of the birds and 75 percent of the mammals that are snagdependent in Southwestern forests are insectivorous. This 

diet preference is important because birds and mammals 

have been credited with insect control that helps maintain ecosystem functioning. 

An important interaction exists in ponderosa pine forests involving the location and suitability of potential nest 

trees, the type and number of primary cavity excavating 

species (especially woodpeckers), and the number and 

distribution of secondary cavity nesting species. Although 

secondary cavity nesting species will use non-bird excavated holes (for example, holes resulting from disease or 

broken branches) for nesting, their frequent use of birdexcavated holes indicates a likely preference for such cavities or a limitation of alternative nest sites. 

Brawn and Balda (1988b; see also Brawn 1985, Brawn 

and Balda 1983) tested the common assumption that nest 

sites limit the breeding density of secondary cavity nesters in an Arizona ponderosa pine forest. They found this 

assumption to be only partially correct. They found that 

secondary cavity nesters, as a group, can indeed be limited by nest sites. But only three of the six species they 

studied significantly increased in density when provided 

with artificial nest boxes; these were the violet-green swallow, pygmy nuthatch (which can also be a primary cavity-nesting species), and western bluebird. Numbers of 

house wrens, mountain chickadees, and white-breasted 

nuthatches did not differ. They concluded that a given 

population appears to be limited by nest sites if it is sufficiently common during the breeding season and dependent upon snags as a source of nest sites. Within species 

that are nest site limited, availability of food or foraging 

substrates and territoriality may determine an upper limit 

to breeding densities if nest sites are in ample supply. Thus, 

a dynamic exists between nest sites, food availability, and 

intra- and interspecific competition for nest sites. 

A study of secondary cavity nesters in northern Arizona by Cunningham et al. (1980) found pronounced inUSDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 4 

terspecific variation in the use of snags for nest sites; certain species were reliant on snags, whereas others rarely 

used snags. For example, nearly all violet-green swallows 

and pygmy nuthatches nested in snags, whereas whitebreasted nuthatches were not so dependent upon snags. 

Cunningham et al. also found that mountain chickadees, 

white-breasted nuthatches, and house wrens were relatively uncommon regardless of the availability of snags 

and foraging substrate. It is the common species that seem 

to increase the most after provision of nest boxes. Brawn 

and Balda (1988b) speculated that this was because relatively rare populations do not contain enough nonbreeding individuals (that is, floaters) to be able to take 

advantage of the increase in nesting sites. Common species thus can be nest-site limited, whereas rare species are 

being suppressed by other factors. Brawn et al. (1987) also 

found that, during the breeding season, interspecific competition for food among secondary cavity nesters appeared 

to be unimportant in ponderosa pine bird communities. 

The factors holding down numbers of rare species are still 

generally unknown. 

There is apparently an interaction between the species 

of snag retained after treatments and the response of birds 

to total snag density. Scott (1979) found that populations 

of some species of cavity-nesting birds can be reduced significantly by removal of conifer snags even when some 

aspen snags are left. Other hardwoods, such as oak, provide nesting sites for some species of birds within the 

ponderosa pine type. Some birds such as swallows, however, may not make the change from ponderosa pine snags 

to the smaller hardwood snags. 

Hay and Guntert (1983) examined the seasonal requirements for snags by pygmy nuthatches in northern Arizona ponderosa pine forest. They found that trees with 

nest cavities were shorter and consequently had a small 

diameter at breast height (dbh) compared to those used 

for roosting during other seasons. Greater cavity height 

of the fall and spring roosts compared to summer roosts 

was related to more absorption of spring-fall radiation by 

the former. In contrast, nest cavities appeared to be positioned to obtain moderate insolation and shielding from 

the wind. Hay and Guntert stated that cavity selection is 

interrelated with the overall biology of the species, and 

management should emphasize snag and/or cavity quality, rather than the absolute quantity of snags available. 

They also concluded that additional baseline research into 

the seasonal quality of cavities and snags needed for cavity-dependent species in ponderosa pine forests was 

needed. 

Horton and Mannan (1988) studied the interrelationship between fire and snag dynamics in southeastern Arizona ponderosa pine and mixed pine-oak forest. Natural 

fires burned every 2 to 12 years in Southwestern ponderosa pine before suppression by humans beginning in the 

late 19th century (for more details, see Moir et al. and Finch 

et al., this volume). These fires were usually light surface 

fires that produced generally open, park-like conditions. 

Modern forest management uses broadcast understory 

fires to reduce accumulations of woody debris left by logging or natural processes to reduce the risk of catastrophic 

crown fires. These fires also impact snag dynamics by consuming existing snags and creating others by killing trees. 

Horton and Mannan found that a single application of 

moderately intense surface fire resulted in a net decrease 

of 33 pbrcent of snags preferred for nesting. However, no 

species of cavity-nesting bird disappeared in the first 

breeding season following the fires, and only the northern flicker and violet-green swallow declined in abundance. They concluded that these changes were not due 

to a shortage of snags. Their study, however, was conducted for only one year following fire treatment. 

Snag Management 

According to Scott (1978), little information existed on 

management guidelines for cavity nesting birds in Southwestern ponderosa pine forests prior to the late 1970s. 

Before that time, snags were removed during forest harvest because of potential fire and safety hazards, and many 

thought they had poor aesthetic value and were indicative of an unhealthy forest. Using his own research and 

that of Balda (1975), Scott (1978) concluded that, on average, at least 2.5 large (243 cm dbh) snags per acre should 

be retained in ponderosa pine forests. In addition, all naturally occurring snags should be left during timber harvest. Specifically, he found that 1) snags usually did not 

become suitable for nesting until 6 years after the trees 

died; 2) snags that retained more than 40 percent of their 

bark were used more frequently and contained more holes 

than those with less bark; 3) snags in higher dbh classes 

(243 cm) were used significantly more than smaller snags 

and the larger snags also contained more holes; 4) snags 

on northern and southern aspects were used at about the 

same frequency, but those on northern exposures averaged more holes per snag; and 5) snags over 23 m tall 

were used at a significantly higher rate than shorter snags, 

but comprised only 16 percent of the available snags. 

Balda (1975) found that 4.2 snags/ha were necessary in 

ponderosa pine forests to achieve average densities and natural species diversity of secondary cavity nesters. He also 

stated that 6.7 snags/ha were necessary to maintain maximum densities and natural species diversity of these birds. 

Ffolliott (1983) examined the implementation of USDA 

Forest Service snag guidelines on study areas across the 

ponderosa pine belt of northern Arizona, examining both 

present conditions and simulated (modeled) conditions 

at the end of a 20-year period. Snags were defined as standing dead trees at least 30 cm dbh and 3.1 m in height; no 

differentiation was made between hard and soft snags. 

His analyses showed that none of his study areas that had 

been subjected to various silvicultural treatments met any 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Songbird Status and Roles 

of the suggested polices for snag retention (USDA Forest 

Service 1977). From his analysis, only virgin forest would 

meet a retention policy of 2.5 to 5.0 snags/ha through 

natural mortality. 

Rosenstock (1996) found that snags >46 cm dbh and >10 

m tall were frequently used for nesting in ponderosa pine 

forest. Cunningham et al. (1980) found a preference for 

snags >58 cm dbh and >20 m tall on the Beaver Creek 

Watershed in northern Arizona. Paine and Martin (1995, 

as cited in Rosenstock 1996) found that 84 percent of ponderosa snags used for nesting on their Mogollon Rim study 

sites were >30 cm dbh and >10 m tall. Horton and Mannan (1988) found a preference for snags >51 cm dbh. 

This review indicates that little research has been conducted on snag requirements in ponderosa pine forests. 

Studies that have been conducted demonstrate that at least 

5 large snags/ha may be necessary to maintain populations of cavity-nesting species. However, it also appears 

that these guidelines are not being attained on at least 

some of the forested lands. 

Predator-Prey RelationshipsIPest Control 

As reviewed by Holmes (1990), numerous bird species 

respond both functionally and numerically to increasing 

prey densities. While birds seem unable to prevent population epidemics of their prey, they do appear to have a 

substantial impact when prey populations are at endemic 

levels. From his review of the literature, Holmes concluded 

that birds could delay the onset of an insect outbreak. For 

example, modeling of spruce budworm populations suggested that predation by birds may be a significant factor 

in maintaining endemic population levels of this species. 

As reviewed by Dahlsten et al. (1990) for western mixedconifer forests (which include ponderosa pine as a major 

component), many species of forest birds concentrate their 

foraging activities on insect species considered to be forest pests. In addition, Koplin (1969) demonstrated a functional response of woodpeckers to insect outbreaks. Insectivorous birds may also increase the fitness of the plants 

on which they forage for arthropod prey. For example, 

Marquis and Whelan (1994) examined the effect of insectivorous birds on white oak (Quercus alba) growth in a 

deciduous forest in Missouri. Through experimental manipulations they demonstrated that the presence of birds 

enhanced the growth of juvenile oaks via bird consumption 

of leaf-chewing insects (primarily Lepidopteran larvae). They 

suggested that forest management practices that promote 

the conservation of insectivorous bird species will help maintain forest productivity. The extension of this to ponderosa 

pine forests (with or without an oak component) is obvious. 

Marquis and Whelan further suggest that although insecticide spraying and handpicking insects off trees can reduce 

their numbers, these are not necessarily feasible alternatives 

for controlling arthropod numbers in forests. 

Insect consumption of cones and seeds can negatively 

impact vertebrate use of such resources. Christensen and 

Whitham (1993) found that stem- and cone-boring insects, 

birds (Clark's nutcrackers, pinyon jays, and [western] 

scrub jays), and mammals competed for pinyon pine 

seeds. And insect herbivores indirectly affected resource 

use by the vertebrates through a 57 percent average reduction in crop sizes. Thus, the foraging of birds on insects plays several important roles and is a significant factor to consider in the management of ponderosa pine 

forests. There is a paucity of information on this subject, 

however, so this is an important area for research. 

Habitat Use 

General Habitat Use 

Balda (1967,1969) studied the use of foliage by breeding birds in ponderosa pine and oak-juniper forests of the 

Chiricahua Mountains, Arizona. He found that certain 

species (such as the pygmy nuthatch) were closely associated with ponderosa pine of many heights, whereas 

other species (such as the chipping sparrow) were found 

in specific height layers regardless of the tree species involved. Other species such as Grace's warbler were restricted to particular heights in pines. The models for pines 

strongly suggested that foliage volume may be an important factor in limiting the densities of the pygmy nuthatch 

and Grace's warbler, even though the former species is a 

cavity nester. Balda (1970) also described the bird community present in oak and oak-juniper-pine woodlands. 

Marshall (1957) summarized surveys he conducted in 

pine-oak woodlands during the summers of the early 

1950s from the Pinaleno and Santa Catalina mountains in 

Arizona, south into central Sonora and to the Sierra Madre 

Occidental of northwestern Chihuahua, Mexico. Ponderosa pine entered his pine-oak woodlands only occasionally. The related Apache pine was more frequently encountered on his sites, along with chihuahua pine (I? leiophylla). 

Marshall provided descriptions of the overall relationship 

between the distribution of birds and plants in the region 

and summarized his observations in annotated species 

notes. Of particular interest are his observations of pine 

(and pine-oak) forest birds of current special concern, including the thick-billed parrot, buff-breasted flycatcher, 

elegant trogon, spotted owl, and Montezuma quail, because he details the population status and describes the 

habitat affinities of these species. 

Carothers et al. (1973a) edited a volume that summarized the status and general habitat preferences of birds 

in the San Francisco and White mountains of Arizona, 

concentrating on breeding birds. A paper by Haldeman 

et al. (1973) included a brief section on wintering birds, 

where 18 species were observed during the winter in ponderosa pine forest, and 69 species were observed during 

summer, of which 23 were known to nest. They considUSDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 77 
Chapter 4 

ered the following species to be exclusive users of the 

ponderosa pine forest during their study in this region: 

solitary vireo, western bluebird, and Brewer's blackbird. 

The pygmy nuthatch, violet-green swallow, American 

robin, white-breasted nuthatch, and Grace's warbler were 

considered to be "characteristic" of ponderosa pine forest 

(that is, found to be two to three times as abundant than 

in a comparison area). 

Franzreb published a series of papers (1978,1983,1984) 

that detailed results of her study of birds in a mixed Douglas-fir, ponderosa pine, and Southwestern white pine 

forest in the White Mountains, Arizona. In this mixed-co- 

- Afer forestshefound that pnderosapine and Southwest- - - 

ern white pine were used less frequently than expected - 

based on total foliage volume, whereas use exceeded availability for Douglas-fir, white fir, and Engelmann spruce. 

She also showed, however, that certain species, especially 

the Grace's warbler, relied upon pines for foraging. 

Franzreb's 1978 and 1983 papers also discussed the influence of logging on bird abundance and foraging behavior. Her 1984 paper detailed the foraging behaviors of the 

ruby-crowned and golden-crowned kinglets. Both species 

strongly preferred spruce and Douglas-fir and avoided 

pines for foraging. 

Salomonson and Balda (1977) examined the winter behavior of the Townsend's solitaire in a pinyon-juniperponderosa pine ecotone in northern Arizona. Territory 

size, and ultimately survival, were related to the abundance of juniper berries. Laudenslayer and Balda (1976; - alsotaudenilayer I9732 studied the breeding birds of-a - 

pinyon-juniper-ponderosa pine ecotone in northern Arizona. They concentrated on five bird species and described 

their densities, foliage preferences, and foraging habitats. 

The mountain chickadee and solitary vireo preferred ponderosa pine; the bushtit and plain titmouse preferred pinyon-juniper; and chipping sparrows were found throughout the ecotone. 

Overturf (1979) compared the breeding bird communities on burned and unburned sites in ponderosa pine of 

northern Arizona. The burned sites showed a decreased 

number of bird species and bird abundance, which were 

related to the decrease in habitat heterogeneity and loss 

of the canopy and shrub-sapling vegetation layer. In addition, burning caused a shift in bird species composition 

from foliage users to ground-using birds because burn- 

- ingcaused an increase in herbaceous plants: Overturf con- - - 

cluded that burning in this "pyroclimatic monocdture" 

would be an effective management strategy because it 

simulated natural fires and increased the overall habitat 

heterogeneity in the forest (for more details, see Finch et 

al., this volume). 

Szaro and Balda (1979, 1986) and Szaro et al. (1990) 

found that significant temporal variations occurred in 

habitat use and foraging behavior of ponderosa pine birds 

in northern Arizona. Szaro and Balda (1986) showed that 

bird density and species richness were influenced by both 

weather and timber harvest. The effects of weather on 

birds varied depending on the type of timber harvest conducted, although the harvest type was of primary importance in determining community structure. The impact of 

harvest was clearly more pronounced after the mildest 

winter and tended to be minimized after the severest winter. They concluded that studies must be conducted during a variety of weather conditions (over many years) to 

determtne the trend of bird responses in different forest 

types (including different harvest types). Similarly, Szaro 

et al. (1990) showed that weather and harvest type significantly influenced foraging behaviors of ponderosa pine 

birdsover a three-year period. They urged that studies be - - 

conducted that identified the proximate mechanisms that 

caused this variation in foraging behavior. They suggested 

that such causes would include resource availability, 

weather conditions, predation, and plant phenology. 

Szaro and Balda (1982) summarized the habitat preferences of ponderosa pine forest species based on their study 

of various seral stages (see also Szaro and Balda 1986; 

Szaro et al. 1990; and as summarized above). The disturbance regime they used to simulate seral stages ranged 

from uncut, mature forest to severely thinned forest (see 

table 4). Six species (of 25 total species, or 24 percent) 

showed no distinct habitat preferences: the northern 

flicker, hairy woodpecker, Steller's jay, common nighthawk, mourning dove, and white-breasted nuthatch. Six 

species (24 percent) preferred undisturbed or only lightly 

thinned-maiure forest~the red-fared warbler, hermit - - 

thrush, Cordilleran flycatcher, pygmy nuthatch, violetgreen swallow, and black-headed grosbeak. Similarly, two 

additional species (8 percent; dark-eyed junco and mountain chickadee) preferred undisturbed to moderately disturbed (cut) forest, and another four species (16 percent) 

preferred lightly to moderately disturbed areas (Grace's 

warbler, yellow-rumped warbler, western tanager, western bluebird). Thus, up to 18 species (72 percent) seemed 

to prefer mature forest with some disturbance (includes 

those species showing no distinct preferences). An additional six species (24 percent) preferred lightly to heavily 

disturbed (chipping sparrow and solitary vireo), moderately to heavily disturbed (western wood-pewee, American robin, and broad-tailed hummingbird), or heavily disturbed (rock wren) areas. Finally, the acorn woodpecker 

was confined to oak groves. The authors concluded that 

thehermitthrush, red-faced warbkr, Cordilleran-fly= - - 

catcher, and pygmy nuthatch showed strong preference 

for undisturbed to only slightly disturbed forest. 

Stallcup (1968) studied habitat segregation of foraging 

nuthatches and woodpeckers in a Colorado ponderosa 

pine forest and described the density and composition of 

this group of birds throughout the year. Birds studied were 

the white-breasted, red-breasted, and pygmy nuthatches, 

hairy woodpecker, northern (red-shafted) flicker, and 

78 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Songbird Status and Roles 

Table 4. Habitat preferences of birds in selected ponderosa 

pine stands in northern Arizona (from Szaro and Balda 

1982). The disturbance regime ranged from (in increasing 

intensity of disturbance): untreated mature forest, 

silviculturally cut, irregular strip cut, to severely thinned cut. 

Preference 

Species 

None 

Northern flicker 

Hairy woodpecker 

Steller's jay 

Common nighthawk 

Mourning dove 

White-breasted nuthatch 

Nondisturbed or lightly disturbed areas 

Red-faced warbler 

Hermit thrush 

Cordilleran flycatcher 

Pygmy nuthatch 

Violet-green swallow 

Black-headed grosbeak 

Nondisturbed to moderately disturbed areas 

Dark-eyed junco 

Mountain chickadee 

Moderately to heavily disturbed areas 

Western wood pewee 

American robin 

Broad-tailed hummingbird 

Heavily disturbed areas 

Rock wren 

Lightly or moderately disturbed areas 

Grace's warbler 

Yellow-rumped warbler 

Western tanager 

Western bluebird 

Lightly to heavily disturbed areas 

Chipping sparrow 

Solitary vireo 

Oak groves 

Acorn woodpecker 

Williamson's sapsucker. Red-naped sapsuckers, downy 

woodpeckers, and northern three-toed woodpeckers were 

present but rare. The absence of the red-breasted nuthatch 

during breeding may have resulted from a shortage of nest 

sites, or more likely, a lack of foraging space because of competition from other species. Stallcup suggested that food 

shortages might be responsible for segregating bird species. 

Apparently the most recent study available on the general habitat affinities of ponderosa pine birds was conducted by Rosenstock (1996). He noted that previous studies on the effects of forest treatments on birds in 

Southwestern ponderosa pine (for example, Szaro and 

Balda 1979) examined treatments that are no longer in 

common use (for example, clear-cuttings, strip cuttings). 

As such, he examined the abundance of birds across a 

wider gradient of pine and pine-oak sera1 stages than had 

previously been conducted. In summary, he found 43 species in pine-oak, and 38 in pine. Two rather uncommon 

species (Clark's nutcracker and evening grosbeak) were 

found only in pine, whereas seven species were unique to 

pine-oak (dusky flycatcher, downy woodpecker, lesser 

goldfinch, rock wren, spotted towhee, Virginia's warbler, 

an4 warbling vireo), and all but the Virginia's warbler 

were rare or uncommon. Four common species-acorn 

woodpecker, black-headed grosbeak, house wren, and redfaced warbler-were found primarily in pine-oak. Densities of violet-green swallows and western wood pewees 

were higher in pine patches, whereas American robins, 

hermit thrushes, and white-breasted nuthatches were 

more abundant at pine-oak sites. By vegetative structural 

stage (VSS; see Moir et al., this volume, for definitions of 

VSSs), neotropical migrant abundances and species richness were similar across VSS classes at pine-oak sites but 

were highest at VSS class 4 and 6 in pine. Residents and 

short-distance migrants had similar abundances and species richness in all VSS classes in pine-oak. At pine sites, 

however, abundance of these groups of species was lower 

in VSS class 3 stands but similar in all other classes; class 

6 had a higher species richness than the other classes. Cavity nesting species had similar abundances and richnesses 

across all pine-oak classes, and across all pine classes except 

class 6, which had considerably higher values. 

Although Rosenstock noted that previous studies in 

Southwestern ponderosa pine were conducted before the 

importance of spatial variables on bird communities was 

widely acknowledged, he was not able to determine the 

influence of patch size and other spatial attributes on the 

bird community he studied. 

Nesting Habitat 

Martin (1988) studied the ability of nest predation to 

explain patterns of covariation in species numbers with 

area and habitat in mixed ponderosa pine forest and 

maple-dominated stands in central Arizona. Variation in 

numbers of species among drainages was positively correlated with variation in the density of foraging and nesting substrates. His results were consistent with a prediction that birds select nest sites based in part on the 

availability of sites that minimized their risk of nest predation, and that these sites increase in number with density of foliage at nest height. His results were also consistent with a hypothesis that availability of suitable nest sites 

is one of the bases for the relationship between species 

numbers and foliage density for foliage-nesting species. 

In a related study, Martin and Roper (1988) detailed their 

findings for the hermit thrush. They found that hermit 

thrushes had low nesting success (7 to 20 percent), due 

mostly to nest predation. The structure of vegetation 

around the nest influenced the predation rate and likely 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 79 
Chapter 4 

the nest-site availability. Likewise, Li and Martin (1991) 

presented results from the same study region for cavitynesting species. Although aspens accounted for only 12 

percent of all trees present in the study area, dead aspen 

accounted for 88 percent of all nest sites. Li and Martin 

also identified specific aspen-conifer patches that were 

chosen for nesting and foraging. Nest cavity height influenced nesting success, with the lower nests showing the 

lowest success. The authors noted that populations of cavity nesters might decrease if aspen snags decreased in 

height and abundance; alternative conifer snags were rare 

because most large trees were harvested before they died. 

Siege1 (1989) examined the distribution and abundance 

of birds in virgin old growth and mature managed ponderosa pine forest in northern Arizona (table 1). The mature managed stands met the "minimum" USDA Forest 

Service standards for old-growth forest. Siegel reached the 

following conclusions. First, brown creepers used large 

(>20 inches dbh) snags, in denser stands of older trees, 

with large pieces of sloughing bark. Such conditions provided the necessary microsites for nest placement and also 

served as foraging sites. Second, hermit thrushes nested 

in the canopies of mature trees, in contrast to the much 

smaller trees this species uses in other parts of its range. 

Siegel felt that small pine were not used because they did 

not provide the necessary support branches for their nests 

nor the foliage necessary to conceal the nests. He also 

thought that placement of nests in the canopy served better to regulate nest temperatures. In addition, hermit 

thrushes also foraged in moist, cool sites. Third, a higher 

total density of birds was found in dense stands of pine 

compared to other stands and was apparently due to the 

greater abundance of aspen and the concomitant wetter 

conditions in these stands. The warbling vireo, violetgreen swallow, western wood-pewee, Williamson's sapsucker, and three-toed woodpecker were more common 

in the dense stands because they used the groves of pineaspen for nesting and foraging. Also, the mesic, dense 

stands may have supported higher bird abundances because of their greater total foliage volume, and concomitantly, higher densities of invertebrate prey. In contrast, 

species richness was only slightly higher in older and 

denser stands, indicating that this situation did not follow the standard positive relationship between foliage 

height diversity and bird species diversity. 

Finally, Siegel (1988) concluded that the mesic conditions created in dense old growth likewise created conditions that were more characteristic of forests at higher 

elevations or latitudes (that is, Canadian and Hudsonian 

life zones). These conditions apparently provided the resources used by the brown creeper, hermit thrush, tlueetoed woodpecker, northern goshawk, and saw-whet owl in 

ponderosa pine. Warm and dry exposures in more open oldgrowth stands were either unsuitable or marginal locations 

for these species. 

McEllin (1979) compared the demography, territorial 

spacing, and foraging behavior of white-breasted and 

pygmy nuthatches in Colorado ponderosa pine and mixed 

ponderosa pine-aspen stands. White-breasted nuthatches 

nested primarily in natural cavities in live pines, whereas 

pygmy nuthatches nested in pre-existing cavities in dead 

pines; cavity availability was higher for the latter species. 

Significant differences were shown for the foraging behaviors,within sexes of each species and between species: 

differences in foraging heights, and foraging locations 

within trees (for example, limbs versus trunks). McEllin 

concluded that these species exploited different aspects 

of forest structure; that is, white-breasted nuthatches were 

more specialized in the vertical, horizontal, and tree structure dimensions, whereas pygmy nuthatches showed 

greater specialization in food items and prey acquisition 

behaviors. With regard to forest management, McEllin 

stated that careful analyses of these ecological relationships 

is a necessary requirement of any program. Artificial reproduction of favorable conditions for one species or one season might result in unfavorable conditions for another species or season. Detailed analyses of space utilization patterns 

within and between species under different forest conditions 

can provide ecological information that will be important in 

designing forest management strategies. 

Brawn (1991) studied the reproduction and foraging of 

western bluebirds on two ponderosa pine sites in northern 

Arizona and found that breeding phenology and allocation 

of parental care were adjusted by bluebirds in response to 

local environmental conditions. Brawn also found that feeding rates of nestlings and fledging success were greater on 

the moderately logged site than on the heavily logged site. 

Migrant Use of Ponderosa Pine 

Very little information exists on use of stopover areas 

by migrant birds, including what vegetation types and 

habitats are most important to birds during migration, 

where these sites occur, and how their distribution and 

abundance are changing over time (Moore et al. 1995). 

Also, because more migrants pass through the eastern 

two-thirds of the United States, most of the literature on 

stopover sites concerns eastern migrants. Hence, there are 

few papers describing the specific use of Southwestern 

ponderosa pine forests as stopover sites. For example, 

Phillips et al. (1964) presented information on bird species in Arizona; and although in the species accounts they 

implied that several of the species migrated through ponderosa pine forests in the state, they did not state it explicitly (table 5). Hejl(1994, table 3), summarizing Brawn 

and Balda (1988a), also listed species that occur in Southwestern ponderosa pine forests but did not indicate those 

that were only migrating through the forests. On the other 

hand, Hutto (1985) found that stopover periods for transient (migrant) birds in fall and spring rarely exceeded 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Songbird Status and Roles 

Table 5. Breeding (B), winterlng (W), and probable strictly migrant (M) birds in ponderosa pine forests (with oak or other 

plant species co-dominant) in Arizona and New Mexico, based on Phillips et a/. (1964) and the New Mexico Partners in Flight 

list of sensitive bird species. Includes both Cordilleran (ponderosa pine) and Madrean (ponderosa and Apache) pine-oak 

forest types together. An asterisk (*) indicates a species for which there is some question about its use of ponderosa pine 

when it is in Arizona. 

State 

Species 

Arizona 

Band-tailed pigeon (B) 

Mourning dove (B) 

Whi p-poor-will (B) 

Vaux's swift* (M) 

White-throated swift (B) 

Black-chinned hummingbird (M) 

Broad-tailed hummingbird (B) 

Rufous hummingbird* (M?) 

Allen's hummingbird* (M?) 

Calliope hummingbird (M) 

Rivoli's hummingbird (B) 

Elegant trogon (B) 

Northern flicker (B,W) 

Acorn woodpecker (B,W) 

Lewis' woodpecker (B,M) 

Red-naped spasucker (W) 

Yellow-breasted sapsucker (W) 

Williamson's sapsucker* (B?,W,M) 

Hairy woodpecker (B,W) 

Downy woodpecker (B,W) 

Three-toed woodpecker (B,W) 

Cassin's kingbird (B) 

Sulphur-bellied flycatcher (B) 

Dusky-capped flycatcher (B) 

Black phoebe' (B,W?) 

Buff-breasted flycatcher (B) 

Cordilleran flycatcher (B) 

Southwest willow flycatcher (B) 

Greater pewee (B) 

Olive-sided flycatcher (B,M) 

Western wood-pewee (B) 

Violet-green swallow (B) 

Tree swallow* (B?) 

Rough-winged swallow (B) 

Purple martin (B) 

Steller's jay (B,W) 

Western scrub jay* (M?) 

Mexican jay (B,W) 

Common raven* (B,W) 

Pinyon jay (B,W) 

Mexican chickadee (B,W) 

Mountain chickadee (B,W) 

White-breasted nuthatch (B,W) 

Red-breasted nuthatch (W) 

Pygmy nuthatch (B,W) 

Brown creeper (B,W) 

American dipper* (B,W) 

Winter wren (W) 

House wren (B) 

Canyon wren* (B) 

Rock wren* (B) 

American robin (B,W) 

Hermit thrush (B) 

Eastern bluebird (B,W) 

Western bluebird (B,W) 

Mountain bluebird (B,W) 

Townsend's solitaire (B,M) 

Blue-gray gnatcatcher* (M) 

Golden-crowned kinglet* (W) 

Ruby-crowned kinglet* (M) 

Olive warbler (B) 

Water pipit* (M) 

Cedar waxwing* (M) 

Loggerhead shrike (M) 

Hutton's vireo (W) 

Solitary vireo (B,M) 

Warbling vireo (B,M) 

Orange-crowned warbler (B) 

Virginia's warbler (B) 

Yellow-rumped warbler (B,M) 

Townsend's warbler (M) 

Hermit warbler (M) 

Grace's warbler (B) 

Common yellow-throat* (M) 

Red-faced warbler (B) 

Wilson's warbler* (M) 

Painted redstart (B) 

Red-winged blackbird (B,W) 

Brown-headed cowbird (B) 

Bronzed cowbird (B 

Western tanager (B,M) 

Hepatic tanager (B) 

Black-headed grosbeak (B,M) 

Evening grosbeak (B,W) 

Red crossbill (B,W) 

Cassin's finch (B,W) 

House finch* (B,W) 

Pine siskin (B) 

Lesser goldfinch (B,W) 

Green-tailed towhee* (B) 

Spotted towhee (B) 

Savannah sparrow* (W) 

Lark sparrow* (B) 

Tree sparrow* (W) 

Chipping sparrow (B,M,W) 

Dark-eyed junco (B,M,W) 

Yellow-eyed junco (B,W) 

White-crowned sparrow* (M) 

Lincoln's sparrow* (B) 

Song sparrow* (B,W) 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 

State 

Species 

New Mexico Red-tailed hawk (B,W) 

Virginia's warbler (B) American kestrel (B,W) 

Olive-sided flycatcher (B) American robin (B,W) 

Grace's warbler (B) 

Band-tailed pigeon (B) 

Red-naped sapsucker (B,W) 

Willow flycatcher (B) 

Hammond's flycatcher (B) 

Peregrine falcon (B) 

Williamson's sapsucker (B,W) 

Dusky flycatcher (B) 

Cordilleran flycatcher (B) 

Olive warbler (M) 

Hepatic tanager (B) 

Broad-tailed hummingbird (B) 

Cassin's kingbird (B) 

Western bluebird (B,W) 

Townsend's solitaire (B,W) 

Northern goshawk (B,W) 

Flammulated owl (B) 

Mountain bluebird (B,W) 

Swainson's thrush (B) 

Wilson's warbler (B) 

Cooper's hawk (B,W) 

White-throated swift (B) 

Magnificent hummingbird (M) 

Greater pewee (M) 

Purple martin (B) 

Golden-crowned kinglet (B,W) 

Hermit thrush (B,W) 

Veery (B) 

Warbling vireo (B) 

Orange-crowned warbler (B) 

Western tanager (B) 

Black-headed grosbeak (B) 

Sharp-shinned hawk (B,W) 

Western wood-pewee (B) 

Cassin's finch (B,W) 

Ash-throated flycatcher (B) 

Tree swallow (B,W) 

Violet-green swallow (B) 

Ruby-crowned kinglet (B,W) 

Spotted towhee (B,W) 

Chipping sparrow (B) 

Lincoln's sparrow (B) 

Brown creeper (B,W) 

Yellow-rumped warbler (B,W) 

Northern flicker (B,W) 

Dark-eyed junco (B,W) 

Pine siskin (B,W) 

House wren (B) 
Chapter 4 

four to six days in pine (mostly Apache; P. engelrnanii) and 

other vegetation in the Chiricahua Mountains, Arizona; 

and Moore et al. (1995) demonstrated that riparian or riverine areas in the southwest are vital for Southwestern 

migrants, notably the woodland species. 

In general, stopover sites are used for depositing and 

replenishing lipid stores, molting, and resting (Moore et 

al. 1995). Stopover sites are crucial to a migrant bird's survival, especially long-distance migrants. Migration, although it allows birds to avoid overwintering in harsh 

environments, also has large costs associated with it, including the high energetic demands of transport (espe- - cially whenthere are climatic stresses); the multiplead-- 

justments necessary to exploit unfamiliar sites; the 

conflicting demands of predator avoidance and food acquisition at stopover sites; and competition with other 

migrants and resident species for resources (Morse 

1989:205; Moore et al. 1995). 

Various features may cue migrants into selecting stopover sites in ponderosa pine forests, such as the proximity to riparian corridors, the forest structure, or the feeding rates or numbers of other migrants at sites (Moore et 

al. 1995). In a study of spring migrants crossing the Gulf 

of Mexico, Moore et al. (1995) found that the birds clearly 

selected areas with greater structural diversity following 

the flight. The areas were comprised of forests with complex mixed-shrub layers and contained the greatest diversity and abundance of migrants. However, Morse 

- 

(1989:96) summarized studies of habitat selection by migrating warblers and foun&thaT habitat selection issubject to immediate and major fitness payoffs, indicating that 

selection of stopover sites may be influenced by factors 

other than vegetative structure. Climate changes, for example, may affect the choice of stopover sites, and ultimately wintering sites. Terrill and Ohmart (1984) found 

that the wintering ranges of yellow-rumped warblers differed from year to year in Arizona and adjacent Mexico 

apparently because the birds were retreating farther south 

in years when the winters were severe. 

The amount of habitat actually available to migrants 

along the migration route is probably inherently limited, 

however, because migrants cannot take the time to search 

extensively for the "best" stopover sites (Moore and 

Simons 1992). This is due to a bird's need to reach the 

breeding area before it is saturated with conspecifics, or - to reach the wintering area before the onsetof severe - 

weather. Studies of warbler species have demonstrated 

that some species use stopover sites that resemble those 

used on the breeding grounds, whereas other species do 

not use similar sites (reviewed in Morse 1989, chapter 9). 

Furthermore, the distributions of migrant birds are often 

correlated with changes in food availabilities (Morse 1989; 

Martin and Karr 1990; Moore et al. 1995). Because migration is a period of exceptional energy demand, it probably exerts strong selective pressures on the maximization of foraging efficiency (Moore and Simm 1985). Hutto 

(1985) found that the distribution of most insectivorous 

migrant birds in the Chiricahua Mountains, Arizona, was 

correlated with the abundance of arthropods in those vegetation types. He concluded that birds forage where they 

can be most efficient, unless interspecific competitive interactions force them to modify their first choice. 

Species of Special Concern in 

Ponderosa Pine Forests - - - 

In this section we summarize current information on 

species of special concern in Southwestern ponderosa pine 

forests. To identify such species, we consulted the 1995 

Arizona Partners in Flight (AZPIF) and 1994 New Mexico 

Partners in Flight (NMPIF) lists of sensitive breeding and 

wintering terrestrial bird species in the states. For these 

lists, bird species were ranked according to scores derived 

from their local and global distributions and abundances; 

the severity of threats on their breeding and wintering 

grounds; and the "importance" of Arizona and New 

Mexico to their overall distributions. 

AZPIF and NMPIF also summarized the primary vegetation associations used by each bird species. The lists 

were created based on species accounts in the literature 

(for example Phillips et al. L964), as~ell asunpublished 

data. We did not consult state wildlife agency publications 

on threatened and sensitive species (for example, Threatened 

Native Wildlife in Arizona, Arizona Department of Game 

and Fish, 1988; BISON-M database, New Mexico Department 

of Game and Fish, 1996) because Atwood (1994) demonstrated that these publications were often incomplete and 

erroneous. We caution that the AZPIF and NMPIF lists may 

also suffer from the same weaknesses, but at a minimum the 

lists have been reviewed by authorities who are familiar with 

the distribution of birds in each state. 

Arizona 

Species of special concern received ranks from 1 to 100. 

Of the approximately 240 species given ranks in Arizona, 

100 of these use ponderosa pine for breeding, wintering, - - - 

and/or migratingof these hundred, 11 specieswere givenranks 150 (table 6), indicating that they are very high priority species-ones of special concern in the state-either 

because of low local or global abundances; restricted global or Arizona breeding distributions; substantial potential for extirpation on the breeding or wintering grounds; 

and/or a high importance of Arizona to the total breeding distribution of the species. Of these species, the whippoor-will, elegant trogon, buff -breasted flycatcher, and sulUSDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Songbird Status and Roles 

phur-bellied flycatcher are at the northern edge of their 

ranges in Arizona, with the majority of their numbers occurring in Mexico. Atwood (1994) suggested that the inclusion of these species based solely on their limited occurrence at the northern extension of their ranges may 

ultimately divert research and management attention that 

should be given to truly threatened species. Two species 

on the list, the southwest willow flycatcher and olive-sided 

flycatcher, have shown declines in the state (and elsewhere), probably due to habitat destruction, and for the 

willow flycatcher, cowbird parasitism (Robinson et al. 

1995). The remaining species on the list were placed there 

because of perceived moderate to extensive threats on the 

breeding and/or wintering grounds, and/or localized and 

isolated breeding distributions. 

Another 20 ponderosa pine species were given ranks 

between 51 and 100 (table 6), indicating that they are of 

moderate concern but not exposed to threats as severe as 

the species with scores 150. These species were mostly 

considered uncommon (in abundance) in Arizona and 

globally. They were also considered to have moderate 

threats on their breeding and/or wintering grounds. 

The 69 remaining species had ranks >loo, indicating 

that their populations may be stable. 

New Mexico 

Of the 156 total species given ranks in New Mexico, 52 

of these use ponderosa pine for breeding, wintering, and/ 

or migrating. Of these fifty-two, 31 species were given 

ranks >2.50 (table 6) by NMPIF, indicating that they either had experienced declines in abundances over the past 

26 years; their trends were unknown; they had low local 

or global abundances; they had restricted global or New 

Mexico breeding distributions; there was substantial potential for extirpation on the breeding or wintering grounds; 

and/or New Mexico is important to the total breeding distribution of the species. Of the special concern species occurring in ponderosa pine forests, only the peregrine falcon 

is currently listed as federally endangered or threatened. 

Another 12 species occurring in ponderosa pine were given 

ranks between 2.10 and 2.45 (table 6), indicating that their 

status is of moderate, rather than high, concern in the state. 

Comparison of Lists 

In both Arizona and New Mexico, the (southwest) willow flycatcher, olive-sided flycatcher, olive warbler, 

Virginia's warbler, and Grace's warbler were given high 

priority ranks. The NMPIF database listed six species of 

high concern that were considered of only moderate concern in Arizona: the band-tailed pigeon, Cordilleran flycatcher, greater pewee, Townsend's solitaire, orangecrowned warbler, and hepatic tanager. The NMPIF list also 

contained an additional 21 species of high concern, versus Arizona's six other species of high concern. For species of moderate concern, the AZPIF database listed anTable 6. Southwestern ponderosa pine forest birds in 

Arizona and New Mexico with ranks indicating that they are 

of high or moderate concern In each state. Criteria for 

rankings are given in the text. 

Rank 

Species 

Arizona 

so 

Whip-poor-will 

Elegant trogon 

Buff-breasted flycatcher 

Southwest willow 

flycatcher 

Olive-sided flycatcher 

Olive warbler 

Solitary vireo 

Virginia's warbler 

Red-faced warbler 

Sulphur-bellied 

flycatcher 

Grace's warbler 

51 -1 00 

Band-tailed pigeon 

Northern (glided) flicker 

Lewis' woodpecker 

Red-naped sapsucker 

Yellow-breasted 

sapsucker 

Williamson's sapsucker 

Three-toed woodpecker 

Cordilleran flycatcher 

Greater pewee 

Tree swallow 

Pygmy nuthatch 

Eastern bluebird 

Townsend's solitaire 

Loggerhead shrike 

Orange-crowned 

warbler 

Painted redstart 

Hepatic tanager 

Lazuli bunting 

Red crossbill 

Green-tailed towhee 

Rank 

Species 

New Mexico 

>2.50 

Virginia's warbler 

Olive-sided flycatcher 

Grace's warbler 

Band-tailed pigeon 

Red-naped sapsucker 

Willow flycatcher 

Hammond's flycatcher 

Peregrine falcon 

Williamson's sapsucker 

Dusky flycatcher 

Cordilleran flycatcher 

Olive warbler 

Hepatic tanager 

Broad-tailed hummingbird 

Cassin's kingbird 

Western bluebird 

Townsend's solitaire 

Northern goshawk 

Flammulated owl 

Mountain bluebird 

Swainson's thrush 

Wilson's warbler 

Cooper's hawk 

White-throated swift 

Magnificent hummingbird 

Greater pewee 

Purple martin 

Golden-crowned kinglet 

Hermit thrush 

Veery 

Warbling vireo 

Orange-crowned warbler 

2.1 0-2.45 

Western tanager 

Black-headed grosbeak 

Sharp-shinned hawk 

Western wood-pewee 

Cassin's finch 

Ash-throated flycatcher 

Tree swallow 

Violet-green swallow 

Ruby-crowned kinglet 

Spotted towhee 

Chipping sparrow 

Lincoln's sparrow 

USDA Forest Service Gen.Tech. Rep. RM-GTR-292. 1997 
Chapter 4 

other 14 beyond the six mentioned above, whereas New 

Mexico had only 12 total species listed (table 6). 

Changes in Abundance 

Hejl(1994), summarizing Brawn and Balda (1988a), proposed that 15 Southwestern ponderosa pine forest bird 

species have probably decreased in abundance from 

presettlement times to the present because of decreases 

in the prevalence of these forest conditions. Hejl based 

this on the birds' requirements for burned sites, oldgrowth forests, and/or snags. The species were the broadtailed hummingbird (AZPIF ranking # 113; NMPIF ranking # 48), acorn woodpecker (AZPIF #129), three-toed 

woodpecker (AZPIF #52), purple martin (#116, #82), violet-green swallow (#172, #119), mountain chickadee 

(AZPIF #170), white-breasted nuthatch (AZPIF #206), 

pygmy nuthatch (AZPIF #68), brown creeper (#189, #138), 

western bluebird (#132, #51), mountain bluebird (#160, 

#66), American robin (#225, #156), red-faced warbler (#16, 

#17), chipping sparrow (#205, #129), and lark sparrow 

(#177, #93). For the most part, however, Hejl's projections 

do not coincide with the species of special concern on the 

AZPIF and NMPIF lists, and the purple martin, western 

bluebird, and American robin were shown by Miller (1992) 

to be increasing in Arizona and New Mexico. Hejl(1994) 

also proposed that nine other bird species have probably 

increased in abundance from presettlement times to the 

present because of fire suppression and increased amounts 

of second-growth forests. These species were the Cordilleran flycatcher (AZPIF #74, NMPIF #37), house wren 

(#224, #152), Townsend's solitaire (#98, #52), hermit thrush 

(#150, #85), solitary vireo (#45, #53), Virginia's warbler 

(#33, #11), yellow-rumped warbler (#217, #140), Grace's 

warbler (#49, #16), and western tanager (#145, MI). Miller 

(1992) found that numbers of solitary vireos, Virginia's 

warblers, and Grace's warblers have actually decreased 

in managed ponderosa pine forests. However, Johnson 

(1994) determined that Grace's warblers, painted redstarts, 

and hepatic tanagers have expanded their ranges northward in this century. On the AZPIF and NMPIF lists, these 

latter two species are considered fairly high priority ones 

for study because of their rarity and localization. In addition, the solitary vireo and Virginia's warbler are also ranked 

as species of special concern in Arizona and New Mexico, 

despite Hejl's indications that they should be responding 

positively to habitat changes in Southwestern forests. 

As mentioned previously for the southwest willow flycatcher, a significant factor in the decline of some other 

bird species in the western United States is the increase in 

parasitism by brown-headed cowbirds. This species, along 

with two grackle species, has experienced the greatest rate 

of increase and largest expansion of any native bird species in the United States (Marzluff 1994). There are about 

11 to 20 cowbirds per Breeding Bird Survey route in Arizona and 0 to 10 per route in New Mexico (Robinson et al. 

1995). Because of their parasitic nature, cowbirds can breed 

in a wider range of vegetation types than probably any 

other North American passerine (Robinson et al. 1995). In 

the west, cowbirds occur regularly in coniferous forests 

but in fewer numbers than in other nearby areas such as 

meadows and riparian zones (for example, Rothstein et 

al. 1984). 

Host species of cowbirds tend to be small-sized, opencup-nesting birds with long incubation periods, including Empidonax flycatchers and phoebes, vireos, warblers, 

and sparrows such as the chipping sparrow. Hosts inhabiting forest edges and/or second-growth forests also tend 

to be more heavily parasitized. The largest declines in host 

numbers are seen in species with restricted geographic 

breeding ranges and with habitat that is fragmented, is 

threatened by direct destruction (such as that of the southwest willow flycatcher), and/or has been subject to fire 

suppression (reviewed in Robinson et al. 1995; see also 

Moir et al., this volume). 

Despite concerns about increased parasitism by cowbirds in the western United States, parasitism has not been 

documented in several birds that would seem to be likely 

candidates. For example, Martin (1992, table 1) summarized reproductive data for neotropical migrant birds in 

Arizona and New Mexico. Black-headed grosbeaks in 

deciduous (oak) forests in New Mexico were not parasitized by cowbirds. Neither were warbling vireos, orangecrowned warblers, Virginia's warblers, yellow-rumped 

warblers, MacGillivray's warblers, red-faced warblers, 

western tanagers, and black-headed grosbeaks in mixedconifer/deciduous forests in Arizona according to several 

recent studies. On the other hand, parasitism rates in other 

small flycatchers and warblers (such as western woodpewees and painted redstarts in Arizona) can be quite high 

(L. Christoferson, unpubl. manuscript, University of Arizona). For example, Marvil and Cruz (1989) documented 

the fate of solitary vireo nests in ponderosa pine/Douglas-fir forests in Colorado. Approximately 49 percent of 

all vireo nests were parasitized with one to three brownheaded cowbird eggs during the breeding seasons of 1984 

1986, leading to a significant decrease in the reproductive 

success of the nests. 

Conclusions 

We found specific information on the use of Southwestern ponderosa pine forests by approximately 50 bird species. However, of these species, only about 35 percent appear to restrict their vegetation use to primarily ponderosa 

pine, whereas about 65 percent are associated with other 

plant components (for example, aspen, oak, Douglas-fir, 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Songbird Status and Roles 

fir, spruce, and pinyon-juniper) within ponderosa pine 

forests. This shows that most ponderosa pine bird species 

require features in addition to pine. It also implies that 

forest management must include consideration of these 

features if the retention of diverse bird communities is 

desired. Although many species are declining in abundance, few species are nearing extirpation. More effort 

could thus be expended on monitoring trends of species 

of special concern and on monitoring their demographies. 

The factors causing the apparent declines are still largely 

speculative and thus need to be investigated. 

In regard to "disturbed" sites (either from fire or logging), bird species showed different responses, although 

most speciesappeared to tolerate (at least in terms of their 

abundances) light to moderate disturbance. With heavy 

alteration of the forest structure (for example, via fires, 

clearcutting, or strip-cutting), species composition varied 

in a predictable way, with more understory species using 

cleared forest stands. Nest predation apparently influenced the placement of nests to the extent that birds selected denser foliage. Nest success-as might be expected-varied among species and study areas, but 

bluebird nesting success decreased on heavily altered sites. 

Forest management must be site- and time-specific and 

management objectives must consider all of the different 

components that are used by the numerous species of 

ponderosa pine forests. Data also indicate a strong need 

for intensive studies of the reproductive success of ponderosa pine birds; without these data, any conclusions 

about the current status or current habitat requirements 

of the species are tenuous. 

We know little specifically about the use of ponderosa 

pine forests by migrating birds. However, we can estimate 

that Southwestern pine forests are probably used as stopover sites by at least 25 migrant bird species in a given 

year. Research on migratory birds in other vegetation types 

suggests that forest structure, food availability, inter- and 

intraspecific competition for resources, and climate conditions all influence the use of these forests by migrant 

species. Therefore, we can probably assume that these 

same factors would influence the use of Southwestern 

ponderosa pine forests as stopover sites. And as such, the 

number of species that may depend on ponderosa pine 

forests for replenishment of lipids or as resting sites makes 

this vegetation type important to their survival. However, 

we need more research on how migratory birds use ponderosa pine forests. Most studies have also concentrated 

on breeding birds; more work needs to be conducted on 

non-breeding (wintering) birds. This information is critical for developing appropriate forest management plans 

because of the role that stopover sites can play in maintaining bird populations. 

Natural expansions and increases in populations of 

some ponderosa pine forest species have been documented (DeSante and George 1994, Johnson 1994); however, a large percentage of species have declined, due probably to various causes. The many factors that may affect 

ponderosa pine songbird numbers (such as fire, logging, 

grazing, and climate change) and the variations in local 

site conditions make it difficult to predict exact trends in 

bird numbers. Again, the implications of this for management of ponderosa pine forests are that one treatment, or 

one management style, will not elicit the same population response from all bird species. Similarly, effects of past 

manigement practices may vary depending on location. 

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USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 5 

Effects of Urbanization and Recreation on Songbirds 

John M. Marzluff 

Introduction 

The world's population has grown to over 5 billion 

people and shows no sign of slowing (Horiuchi 1992). Our 

increasing population and natural resource use is the fundamental reason that much of the natural world is in crisis (Mange1 et al. 1996). In the United States, the greatest 

recent increases in human population are in the Western 

states. Nevada leads in population growth, followed by 

Arizona; New Mexico ranks ninth (U.S. Department of 

Commerce). As a result, human impacts on western bird 

communities, which are already severe (Jehl and Johnson 

1994), will probably increase. 

The human population in the ponderosa pine forests of 

Arizona and New Mexico, although currently low, is on 

the rise due to tourism and retirement industries (Raish 

et al. this volume). Computers have enabled many people 

to conduct business remotely. Work-at-home individuals 

are choosing ponderosa pine forest towns because of their 

small size, safety, cleanliness, scenic beauty, and friendly 

inhabitants (J. Burding, Flagstaff Chamber of Commerce, 

personal communication). Moreover, cool temperatures 

and scenic beauty attract large numbers of recreationists 

to the forests, especially during the summer months when 

desert dwellers want to escape extreme temperatures. 

The importance of ponderosa pine forests as recreation 

sites (Raish et al. this volume) indicates that the potential impacts of humans on the forest will probably 

be greater than resident population censuses might 

suggest. 

Human pressures on ponderosa pine forests will continue to increase (Boyle and Samson 1985; Anderson 1995; 

Flather and Cordel 1995; Raish et al. this volume). The 

potential effects of these increases on songbirds in ponderosa pine forests are not well studied, but many results 

are predictable if human use of the forests can be quantified (Foin et al. 1977). This chapter discusses how urbanization and recreation in Southwestern ponderosa pine 

forests might influence songbirds and comments on the 

research necessary to provide an assessment of future affects. Other important human impacts on ponderosa 

pine forest birds, including fire suppression, logging, 

and grazing, are discussed in Chapters 2,6, and 7 of this 

publication. 

Effects of Urbanization and 

Recreation on Songbirds 

There have been few studies documenting the effects 

of urbanization and recreation on songbirds and only 2 

that test the affects on Southwestern ponderosa pine forests (Aitchison 1977; Yarnell 1993). However, a general 

study review is useful because many affects are consistent over large geographic areas (Rosenberg et al. 1987) 

and are predictable given knowledge of local avian natural history (Foin et al. 1977). 

In this chapter, the words "urban" and "urbanization" 

reference towns and their associated affects. Concentrated 

human presence is the key feature that distinguishes urbanization from other forms of disturbance. 

Urbanization 

Urbanization directly influences songbird populations 

and communities by changing ecosystem processes, habitat, and/or food supply. Urbanization indirectly influences 

songbirds by affecting their predators, competitors, or 

disease organisms. Individual birds may adjust their behavior in response to human factors in urban environments. In forested North America, urbanized habitats typically support larger (measured by biomass) and richer 

(more species) but less even in relative abundance avian 

communities because they are dominated by a few, abundant species (Pitelka 1942; Emlen 1974; DeGraff and 

Wentworth 1981; Rosenberg et al. 1987; Mills et al. 1989). 

Urbanization also favors some species but selects against 

others so that the composition of urban avian communities 

differs from those in native environments (Beissinger and 

Osbome 1982; Rosenberg et al. 1987; Mills et al. 1989; Blair 

1996). While many studies have documented these findings, 

none have specifically measured the effects of urbanization 

on avian demography. Many urban populations may be sink 

(area of population decline) populations (Pulliam 1988) that 

attract many recruits but produce few (Blair 1996). Marzluff 

and Balda (1992) suggested that this was the case for pinyon 

jays in Flagstaff, Arizona during the 1980s, and this is probably also true for many flycatchers, Steller's jays, wrens, 

thrushes, warblers, tanagers, grosbeaks, and sparrows. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 5 

Changes in Ecosystem Processes 

The affects likely to have the greatest impact on ponderosa pine forest birds are changes in the basic functioning 

of the ponderosa pine ecosystem; specifically, reduction in 

natural processes such as fire, altered nutrient cycling, and 

disrupted water cycling. These changes are accentuated by 

urbanization and can lead to long-term forest degradation. 

Existence of buildings has prompted intense efforts to 

suppress fire near urban areas, which disrupts the natural fire regime that has evolved with ponderosa pine forest birds. Detailed discussion of the effects of fire suppression on forest structure and function and forest avifauna 

are in Chapters 1 and 6, respectively. 

The energy and building requirements of humans disrupts the natural nutrient cycling of ponderosa pine forests. Forests are thinned to reduce the fire threat and some 

dead woody material is removed for fuelwood. Loss of 

snags leads to reductions in insectivores, which can lead 

to a reduction in forest health (Hall et al. this volume). 

The combination of fire suppression, logging, and fuel 

wood harvest has created a new, unbalanced nutrient cycle 

where nutrients in living trees are removed from the forest as wood products and nutrients in dead debris are removed as firewood. The most important effect of urbanization on nutrient cycling is probably a lengthening of 

cycles. Fire suppression around urban areas has eliminated 

the primary mechanism of nutrient cycling in ponderosa 

pine forests. The lack of fire causes living and dead biomass to accumulate much faster than it degrades and recycles (Covington and Moore 1994). Prescriptions to reduce the Future fire threat, such as thinning (Edminster 

and Olsen 1996), are then used rather than prescribed 

burning. As a result, the urban pine forest, although accumulating nutrients and energy, typically exports them 

rather than recycles them. This nutrient and energy loss 

may steadily degrade forest growth with long-lasting affect on forest birds. 

Water is an important, often limiting, resource in ponderosa pine forests. Permeable, volcanic soils hold little 

water above ground and permanent streams, lakes, and 

ponds are rare. Runoff patterns are affected by urbanization as native soils are replaced by impermeable concrete 

and surrounding forest substrates are compacted by vehicular and foot traffic. Urban centers have tremendous 

water requirements that affect water distribution and cycling in surrounding forests. Water tables are lowered as 

aquifers are used at greater than replacement rates (Thorn 

et al. 1993; Haneberg and Friesen 1995). As forest health 

declines, springs and seeps important to wildlife may dry 

up causing bird reductions or redistributions. Songbirds 

that are able to tolerate human activity will become increasingly dependent on urban areas for water. 

Habitat Changes 

cally more fragmented, includes less coverage at mid- and 

upper levels, and has more ground level coverage than in 

natural environments (Beissinger and Osborne 1982; Blair 

1996). Not only are patches of vegetation isolated in urban environments, they also rarely include the full complement of species found in natural forests (Beissinger and 

Osborne 1982). Native plant species are often removed 

from urban environments and replaced by exotic ornamentals (Beissinger and Osborne 1982; Rosenberg et al. 

1987). Even moderately urban environments contain few 

standing or downed dead trees to provide nest and foraging sites for cavity nesters and timber drillers. Extreme 

urbanization leads to decreases in vegetation at all levels 

as man-made structures replace vegetation (Blair 1996). 

In heavily urbanized areas, forest structure may be modified well beyond the city boundaries (Kamada and 

Nakagoshi 1993). 

Urbanization in ponderosa pine forests produces most 

of the vegetation effects previously noted. Native shrub 

and oak understories are usually replaced by lawns and 

ornamental shrubs. The ponderosa pine canopy is fragmented by houses and roads, but this forest type is not 

typified by a closed canopy. Even with fragmentation, the 

actual density of trees in and around urban centers is probably much greater than during presettlement times because of smaller average tree size and fire suppression 

(Morgan 1994). Snags and downed woody debris are 

found at low densities in urban ponderosa pine forests 

because of safety, fire, and aesthetic concerns. Exotic junipers and Colorado pinyon pine trees, commonly planted 

in urban yards, supply food for wintering Townsend's 

solitaires, western bluebirds, American robins, and jays. 

However, exotic plant communities disproportionately 

favor a few bird species at the expense of preserving the 

entire native avifauna. Despite these changes, towns in 

ponderosa pine are less likely to modify natural habitat 

than other urban centers (eastern United States, West 

Coast, desert Southwest) because they are modestly sized 

and have housing developments that are often widely dispersed to enjoy the natural scenic beauty. Where heavily 

urbanized areas do occur, opportunities for ground foragers are greatly reduced. 

Direct habitat modification by urbanization in ponderosa pine forests will likely: 1) benefit ground-gleaning 

and probing birds that are tolerant of human activity 

(American robin, European starling, Brewer's blackbird, 

and American crow); 2) benefit species that nest in manmade structures or ornamental vegetation (rock dove, 

house sparrow, European starling, house wren, purple 

martin, barn swallow, house finch, and eastern kingbird); 

3) reduce shrub and canopy nesters and foragers (warblers, vireos, tanagers, grosbeaks, wrens, creepers, chickadees, and nuthatches); and 4) reduce burn specialists, cavity nesters, and bark drillers (olive-sided flycatcher, 

Vegetation in moderately urban environments is typi- swallows, woodpeckers, chickadees, nuthatches,-creepers, 

90 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Effects of Urbanization and Recreation on Songbirds 

and bluebirds). These effects have been noted on similar 

species in other environments (Beissinger and Osborne 

1982; Rosenberg et al. 1987; Mills et al. 1989; Blair 1996). 

Yarnell's (1993) study of annual trends in birds counted 

on Flagstaff's National Audubon Society's Christmas Bird 

Count suggests that urban obligates and grassland species have increased around Flagstaff from 1967 to 1991. 

Food Changes 

Urban centers provide food to birds directly at feeders 

and indirectly at areas of waste treatment, collection, and 

transfer. Seed eaters and nectivores (hummingbirds, jays, 

woodpeckers, chickadees, nuthatches, juncos, sparrows, 

finches, and grosbeaks) benefit from feeders. Scavenging 

omnivores (gulls, jays, crows, and ravens, blackbirds, and 

European starlings) benefit from spilled waste (Robbins 

et al. 1986; Boarman 1993; Marzluff et al. 1994). 

Food resources are also affected indirectly by changes 

in vegetation as previously discussed. In particular, exotic plants have fewer insects than native plants and urban lawns are rich and consistent feeding grounds 

(Rosenberg et al. 1987). These changes favor ground foragers and granivores while selecting against shrub and 

mid-canopy foliage gleaners as previously mentioned. 

Predator Changes 

Introduced predators (cats, dogs) are more abundant 

in urban areas than in native forests and may have substantial affects on the avifauna (Churcher and Lawton 

1987). Other avian predators (sharp-shinned hawk, northern pygmy owl, merlin, and Cooper's hawk) may increase 

in urban areas and concentrate their activities at feeders 

where prey are abundant. Human predators can also seriously deplete local songbirds, sometimes just for sport. 

An example of this occurred in Flagstaff when a teenager 

shooting pinyon jays during one breeding season caused 

most of the nest failure and mortality experienced by the 

flock that year (Marzluff and Balda 1992). Large predators are usually eliminated from areas of human habitation. If northern goshawks in urban ponderosa pine forests are also reduced, songbird populations may increase. 

Coyotes (Canis latrans) and mountain lions (Felis concolor) 

have increased in and around urban areas recently. These 

predators may benefit many songbirds by reducing mammalian nest predators, especially cats (Quinn 1992). 

Perhaps even more important than the increasing mortality experienced by free-flying birds, urbanization reduces nesting productivity by escalating the number of 

predators that destroy bird nests. Nest predation is probably the most important limiting factor on songbirds (Martin 1993a, b), even outweighing winter mortality for migratory species (Bohninggaese et al. 1993). Nest predators, 

often more abundant in urban areas than native habitats, 

have increased dramatically in the Western United States 

during the last century (Robbins et al. 1986; Boarman 1993; 

Marzluff et al. 1994). As predator density increases so does 

the predation rate (Andren 1992; Marzluff et al. 1995). 

Important nest predators in ponderosa pine include 

domestic cats, striped skunks (Mephitus mephitus), rock 

squirrels (Citellus variegatus), Abert squirrels (Sciurus 

aberti), gopher snakes (Pituophis melanoleucus), Steller's 

jays, American crows, and common ravens (Marzluff and 

Balda 1992). Surveys of jays, crows, and ravens conducted 

at several locations in and adjacent to Southwest ponderoBa pine each winter since about 1960, suggest that ravens 

are more abundant and increasing quicker at urban than 

at rural sites (figure 1; Yarnell 1993). Moreover, the greatest densities of ravens in rural areas are at sites near urban areas. Figure Ib shows that Mormon Lake, which is 

25 km from Flagstaff, has the highest density of ravens of 

the rural sites studied. American crows are also more typically abundant at urban than rural sites (figure 2). Crows 

in Flagstaff continued to increase in 1996 (R. Balda, personal communication). However, Prescott, Arizona has yet 

to be colonized by crows and rural areas near urban centers (Sandia Mountains, New Mexico; Mormon Lake, Arizona) are occasionally visited by many crows. Steller's jays 

vary greatly in abundance from year to year at rural and 

urban sites without a consistent tendency to be more abundant in urban sites (figure 3). Other jays, such as scrub 

and Mexican, may actually respond positively to urbanization (Marzluff et al. 1994). These lower-elevation species are invading ponderosa pine towns most notably 

Payson, Prescott, and Flagstaff, Arizona (Yarnell 1993). 

Counts during the breeding season at rural sites (none 

are available for urban sites) suggest that crows, ravens, 

and Steller's jays are common, and that typically urban 

nest predators, such as crows, can be abundant in rural 

sites (figure 4). 

The increasing number of nest predators, especially 

ravens, in urban ponderosa pine forests reduces productivity of native songbirds. Nearly half of all pinyon jay 

nests in Flagstaff failed from predation in the 1980s. This 

was a significant increase over predation in the 1970s and 

was closely correlated with increasing raven populations 

in the city (Marzluff and Balda 1992). Reduced jay productivity led to a decrease in population size and an increased reliance on immigration to sustain the Flagstaff 

population. Thus, the population functioned as a sink 

population during the 1980s although it was probably a 

source (area of population increase) population in the 

1970s. Perhaps other open-nesting songbirds suffer similar fates in urban environments. 

Disease 

Disease rarely regulates temperate bird populations. Urban populations are probably more susceptible to disease 

than those in native forests because artificial feeders concentrate birds and increase the incidence of disease spread. 

Moreover, some urban species, such as rock doves and 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 5 

a) Urban sites 

* Flagstaff, AZ 

4 - Santa Fe, NM 

b) Rural sites 

* Mormon Lake, AZ 

- Grand Canyon, AZ 

--v- Sandia Mtns., NM 

2 

Year 

Figure I. Number of common ravens counted during winter surveys in Southwestern ponderosa pine areas. Birds 

were counted each winter at the same location as part 

of the National Audubon Society's Christmas Bird 

Count. Counts were standardized by observers, which 

varies annually, by dividing the total number of birds 

counted by total observation time (party hours). All 

sites in Arizona and New Mexico that had relatively 

complete counts from 1960 through 1995 were used. 

Sites inside the city limits of urban centers are plotted 

in the top panel and those outside city limits are plotted in the bottom panel. 

blackbirds, may be reservoirs for disease (Garner 1978). 

Rock doves, more common in urban ponderosa pine forests than in natural forests (figure 5; Yarnell 1993), are 

known to carry diseases such as Trichornonas. This protozoan may survive in urban settings better than in rural 

areas because of the large rock dove population. In addi5 

P 1960 1965 1970 1975 1980 1085 1990 1995 

b) Rural sites 

- a) Urban sites C 

+ii d 

3 -e- Sandia Mtns., NM 

8 - Santa Catalina Mtns., AZ 

0 

E 

z 

UJ 

f 2- CI 

V) .- 

2 

0 

- Mormon Lake, AZ I I I --- Grand Canyon. AL 1 

n 

Year - - - - 

-- --- --- --- -- --- 

Figure 2. Number of American crows counted at urban and E-- 

ral sites during the annual National Audubon Society's 

Christmas Bird Counts. Counts were standardized by 

observers, which varies annually, by dividing the total 

number of birds counted by total observation time 

(party hours). All sites in Arizona and New Mexico that 

had relatively complete counts from 1960 through 1995 

were used. Sites inside the city limits of urban centers 

are plotted in the top panel and those outside city limits are plotted in the bottom panel. 

tion, when environmental conditions, such as warm 

springs, favor Trichornonas growth, it is quickly transmitted at communal feeding sites. During the spring of 1996 

in Flagstaff, Trichomonas growth and transmission resulted 

in the death of several evening grosbeaks and pine siskins 

(Bill Watt, Arizona Department of Fish and Game, personal communication). Seed eaters and nectivores are most 

susceptible to such diseases because they frequent urban 

feeders. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Effects of Urbanization and Recreation on Songbirds 

a) Urban sites 

4- Prescotl, AZ - Flagstaff, AZ 1 4 - Santa Fe. NM 

b) Rural sites 

- Mormon Lake, AZ 4 . Grand Canyon, AZ --o- Sandia Mtns., NM 

Year 

Figure 3. Number of Steller's jays counted at urban and rural 

sites during the annual National Audubon Society's 

Christmas Bird Counts. Counts were standardized by 

observers, which varies annually, by dividing the total 

number of birds counted by total observation time 

(party hours). All sites in Arizona and New Mexico that 

had relatively complete counts from 1960 through 1995 

were used. Sites inside the city limits of urban centers 

are plotted in the top panel and those outside city limits are plotted in the bottom panel. 

Competition 

Availability of nest sites helps determine the population density of cavity-nesting birds in ponderosa pine forests (Brawn and Balda 1988). Cavity nest sites are usually 

at a premium in urban sites because of snag removal. The 

increased abundance of European starlings at urban sites 

(Johnston and Garrett 1994) suggests that the limited num- 

- AZ Route.115 

--c - NM Route 3 

0 

30 , Common raven 1 

American crow 

20 , 1 

Year 

Figure 4. Number of nest predators counted during breeding 

season surveys in ponderosa pine forests of New 

Mexico and Arizona. These counts are part of the 

National Biological Service's Breeding Bird Survey 

program that began in 1966. Birds are counted along 

a 49.5 mile route that is driven by an observer once 

per year. The observer counts birds while stopping for 

3 minutes at each of 50 locations spaced at 0.5 mile 

intervals along the route. All routes with fairly complete data in New Mexico and Arizona were in rural 

locations. 

ber of urban cavity nest sites may be difficult for native 

birds to obtain. Starlings commonly outcompete native 

birds for cavities (Feare 1984)' which affects native cavity-nester populations in urban forests. Even the best public intentions can exacerbate this problem; nest boxes for 

native birds often support breeding starlings and house 

sparrows. House wrens may also use these boxes and prey 

on eggs and nestlings of other species. 

Behavioral Adjustment to Urbanization 

Individuals may adjust their behavior in response to 

features of urban environments. Such adjustments may 

enhance a species' ability to persist in the urban environment and may have ramifications beyond the urban setting. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 5 

The best documented behavior changes in urban envi- (Marzluff and Balda 1992). Songbirds that are repeatedly 

ronments involve nesting. Birds breeding in urban envi- disturbed at their nest may increase their aggressiveness 

ronrnents often nest earlier than those in rural environ- (Knight and Temple 1986). Persecution by humans may sements because of supplemental food (Balda and Bateman lect for reduced aggressiveness (Knight et al. 1989). Species 

1972). This may be detrimental in ponderosa pine forests that live closely with humans, such as American crows, may 

where late spring snow storms often destroy early nests become accustom to human presence in urban areas (Knight 

Figure 5. 

a) Urban sites 

* Flagstaff, AZ 'I"" --P - Santa Fe, NM 

b) Rural sites 

* Santa Catalina Mtns., AZ - Mormon Lake, AZ --P - Grand Canyon, AZ I --9- Sandia Mtns., NM 

. - 

et al. 1987). Lncreased nest prehation in urban areas may cause 

some birds to change nest placement to minimize losses 

(Knight and Fitzner 1985; Marzluff 1988). 

Foraking behavior also may be modified in urban environments. Species that use human food sources may reduce their use of natural foods and change their temporal 

and spatial foraging behavior to include provisioning sites. 

Reduced reliance on natural foods may interrupt seed 

dispersal and pollination far beyond the urban center. 

Clark's nutcrackers, for example, are important dispersal 

agents for whitebark pine in Colorado. Nutcracker reliance on human handouts in Rocky Mountain National 

Park may have decreased the dispersal of whitebark pine 

in the region (Tomback and Taylor 1986). This may also 

occur with pinyon pine, which depends on jays, crows, 

and ravens, especially the pinyon jay, for dispersal 

(Marzluff and Balda 1992). However, pinyon jays in Flagstaff that regularly visited feeders, abandoned them in the 

fall when pinyon pine seeds were ripe. They cached seeds 

from the lower elevation pinyon pine forest in the ponderosa forest. Many of the pinyon seeds germinated and 

became established trees. Pinyon pine is now encroaching into ponderosa pine habitat because of the actions of 

this bird. Ironically, the pinyon jay may only survive in 

ponderosa pine forests because of urbanization and 

supplemental food provided at bird feeders. 

Recreation 

Recreation can affect wildlife through harvest, habitat 

modification, predation, and disturbance (Knight and Cole 

1995b). Habitat modification and disturbance are most 

relevant for songbirds because their affects on behavior 

may modify vigor, productivity, or survival of individuals. Individual demographics and behavior may affect 

abundance, distribution, and population viability (Anderson 1995; Knight and Cole 1995b). Populations may influence community organization and interactions among - - Year community members (Gutzwiller 1995). The general effect of and impacts on specific types of recreation in pon- Number of rock doves counted at urban and rural sites derosa pine forests are discussed in this section. 

during the annual National Audubon Society's Christmas Bird Counts. Counts were standardized by ob- Habitat Modification servers, which varies annually, by dividing the total 

number of birds counted by total observation time Habitat modification indirectly affects wildlife and can 

(party hours). All sites in Arizona and New Mexico that have long-lasting effects. Recreationists modify habitat 

had relatively complete counts from 1960 through 1995 primarily and harvesting fire 

were used. Sites inside the city limits of urban centers wood. Trampling from hiking, camping, fishing, and naare plotted in the top panel and those outside city lim- ture study compacts soil, decreases its porosity, and inits are plotted in the bottom panel. creases erosion (Cole and Landres 1995). This, along with 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Effects of Urbanization and Recreation on Songbirds 

vegetation crushing, reduces seed germination, seedling 

establishment, plant growth, and reproduction. Trails may 

be used by predators and parasites, such as cowbirds, to 

gain access to forest interiors. Plant species composition 

often changes in recreation sites as disturbance favors very 

small or very large species, low growing species, species 

with tough leaves, and annuals with rapid growth and 

copious seed production (Cole and Landres 1995). Aboveground vegetation, dead wood, and brush piles are reduced. Plant species diversity is reduced under extreme 

disturbance but may increase with low to moderate recreation levels (Cole and Landres 1995; Blair 1996). 

Recreationists may increase the spread of exotic plants by 

acting as dispersal agents. Habitat contiguity and horizontal and vertical diversity is reduced by recreation. 

Habitat changes will generally cause the greatest reduction in bird species that rely on shrub and ground cover 

(juncos, thrushes, warblers, sparrows, vireos, and wrens) 

and those that depend on standing dead and downed 

woody debris (woodpeckers, secondary cavity nesters). 

Human Disturbance 

Disturbance from recreation on wildlife depends on the 

recreationist and the animals (Knight and Cole 1995a). The 

predictability, frequency, magnitude, timing, and location 

of recreation are important to songbirds. Birds may habituate to predictable disturbances such as walking, driving, or camping in consistent locations. This may reduce 

the recreation disturbance, but it can also be detrimental 

if habituated birds later approach humans and are persecuted (Snyder and Snyder 1974). The potential influence 

of disturbance increases with its frequency and intensity. 

Increases in visitor use of a park in the Netherlands was 

correlated with reductions in songbird density (van der 

Zande and Vos 1984). Most songbirds use ponderosa pine 

forests only during the breeding season, so the timing of 

recreation has important implications. Effects may be especially pronounced during the early part of the nesting 

cycle when nest construction and incubation occur 

(Gotmark 1992). Disturbance during the winter may be 

important to permanent residents, especially when cold 

temperatures and deep snow increase energetic requirements and decrease foraging efficiency. 

Ponderosa pine songbirds are less affected by recreation 

than many animals because of their life history traits. The 

degree of ecological specialization, body size, and sociality of animals may influence their responses to recreation 

(Knight and Cole 1995a). Specialized birds that require 

specific foods or habitats (hummingbirds, cavity nesters, 

pinyon jays, Clark's nutcrackers, and crossbills) are more 

vulnerable to disturbance because they have less ability 

to respond to environmental changes (Croonquist and 

Brooks 1991). The variable temperature, precipitation regime, and seed crops characteristic of ponderosa pine forests (Marzluff and Balda 1992), has favored birds' abilities to exploit alternative resources when necessary. Thus, 

even specialists in ponderosa pine forests may be more 

resilient to change than species in less variable climates. 

This is especially relevant for permanent residents that 

may adjust better to recreational disturbance than migrants. Large animals are more affected by disturbance 

than small ones possibly because of historical persecution 

and energetics (Knight and Cole 1995a). This suggests that 

most songbirds will tolerate recreational disturbance better 

than'larger birds or mammals. Animals that feed in social 

groups may respond quicker to disturbance than solitary 

ones because of increased vigilance and the past experiences 

of other individuals (Knight and Cole 1995a). Therefore, although songbirds in general may tolerate disturbance from 

recreation, social species in ponderosa pine forests (pygmy 

nuthatch, pinyon jay, red crossbill, evening grosbeak, pine 

siskin) may be less tolerant than solitary species. 

The influence of recreation on individuals and populations can affect communities by altering competitive, symbiotic, and predator-prey relationships (Gutzwiller 1995). 

If interacting species differ in their tolerance of humans, 

then recreation may affect some participants more than 

others and unbalance the relationship. Scavenging birds 

include tolerant crows and wary ravens and raptors. In 

one study, disturbance by fisherman favored crows because eagles and ravens quickly flushed when humans 

approached allowing crows to obtain more meat from 

salmon carcasses (Knight et al. 1991; Skagen et al. 1991). 

A similar effect could occur in ponderosa pine forests 

where eagles are flushed by nature viewers from big game 

carcasses during the winter. Recreationists may upset 

predator-prey relationships by disturbing nesting birds 

and advertising nest locations to predators (Gutzwiller 

1995). Predators may be more tolerant of human activity 

than nesting birds or may actually cue in on human activity to locate nests (Gotmark 1992). 

Effects of Recreation in Ponderosa Pine Forests 

Motorized travel and scenery viewing - Although 

motorized travel and scenery viewing are the most popular forms of recreation in Southwestern ponderosa pine 

forests (Raish et al. this volume), they probably have minor, indirect affects on songbirds. Forest fragmentation by 

unimproved roads is unlikely to significantly affect songbird movements because the nonforested areas around 

such roads are small and ponderosa pine forests do not 

naturally have closed canopies. Paved, heavily-traveled 

roads may constrain movement by relatively sedentary 

songbirds, such as winter wrens, and affect their selection of breeding habitat (S. J. Hejl, personal communication). Roads may decrease songbird productivity because 

increased road-kills and litter may subsidize nest predators and provide them with foraging corridors into the 

forest interior (Knight et al. 1995). People stopping at scenic overlooks also may subsidize jays, crows, and ravens 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 95 
Chapter 5 

and perhaps disrupt nearby breeding songbirds. Seedeating songbirds (finches, sparrows, juncos) may benefit 

from roads that concentrate rain water run-off and increase 

annual plant productivity along roadsides. However, such 

benefits may be countered by increases in cowbirds that 

may also use annual plant seeds. 

Camping - Camping, one of the most common forms 

of recreation in Southwestern ponderosa pine forests 

(Raish et al. this volume), is perhaps the most destructive 

recreational pursuit (Jim 1989). Most responses by songbirds to camping are indirect reactions to human intrusion; songbirds respond directly to habitat change and 

food supplementation (Foin et al. 1977). Although these 

responses are usually concentrated in relatively small areas, how far they extend beyond the campground is poorly 

understood. Vegetation in newly established campsites 

usually changes within a year as it is trampled and soil 

becomes compacted (Cole and Landres 1995; Marion and 

Cole 1996). Cover declines, especially in ground and shrub 

layers, and erosion increases. Dead and downed wood is 

quickly scavenged for fires or removed for safety (Foin et 

al. 1977; Cole and Landres 1995). Plant species diversity 

and horizontal and vertical structural diversity decline. 

Bird communities change in response to habitat 

changes. Bird species richness and density increases, but 

evenness of abundance generally declines as campgrounds become dominated by a few widespread, permanent, generalist residents (Foin et al. 1977; Boyle and 

Samson 1985; Guth 1978). Density and diversity declined 

at one Arizona campground immediately after it was 

opened to the public for the summer season (Aitchison 

1977). Brewer's blackbirds, mountain chickadees, Steller 's 

jays, American crows, and common ravens will probably 

increase at campgrounds in ponderosa pine forests, as they 

have elsewhere in the West (Foin et al. 1977; Marzluff et 

al. 1995). However, Aitchison (1977) noted a severe decline in Steller's jays after an Arizona campground was 

opened, primarily because many nests were destroyed by 

removal of trees and slash. Dark-eyed juncos, American 

robins, hermit thrushes, warblers, vireos, wrens, and deep 

forest species will decline as ground, shrub, and midcanopy cover is removed and isolated (Aitchison 1977; 

Foin et al. 1977; Guth 1978; Blakesley and Reese 1988). 

Cavity nesters, bark drillers, and other birds that forage 

on downed woody debris will decline. Productivity of 

open-nesting birds will decline as nest predators and parasites (brown-headed cowbirds) increase in response to 

food supplementation (Clevenger and Workman 1977; 

Rothstein 1994; Marzluff et al. 1995). 

Pack animals have the potential to disrupt ponderosa 

pine forest bird communities. Spilled feed, feces, and litter attracts and supports brown-headed cowbirds that 

parasitize native songbirds reducing their productivity 

(Rothstein 1994). Establishment of pack stations or corrals in remote ponderosa pine locations could pave the 

way for these parasites into areas with minimal human 

disturbance. Warblers, vireos, and flycatchers are most 

susceptible to cowbird parasitism (Rothstein 1994). Although it is unlikely that parasitism alone would cause 

significant declines in such species, it could contribute to 

declines in conjunction with habitat destruction, nest predation, and disruption of ecosystem functioning (Rothstein 1994). 

Hiking, Nature Study, and Wildlife Photography - 

These Aonconsumptive recreational pursuits are usually 

thought inconsequential to wildlife. However, their recent 

surge in popularity (Boyle and Samson 1985; Raish et al. 

this volume) has prompted evaluation of their impacts 

(Boyle and Samson 1985; Riffell et al. 1996). These activities can affect songbirds as humans intrude into their territories to observe nests or unique behavioral activities. 

Nature study and photography may be of special concern 

because they tend to repeatedly disturb rare and unusual 

species (Boyle and Samson 1985). 

Repeated intrusions in songbird territories during the 

breeding season can decrease singing (Gutzwiller et al. 

1994), increase or decrease nest defense (Knight and 

Temple 1986; Keller 1989), and increase predation 

(Gotmark 1992). These changes may reduce the productivity of individuals and influence community composition (Riffell et al. 1996). In fact, intrusion involving 8 to 37 

people/ha/day was correlated with declining songbird 

(warblers, wrens, thrushes) density in the Netherlands 

(van der Zande and Vos 1984; van der Zande et al. 1984). 

More dispersed intrusions (1 person for 1 to 2 hrs/ha/ 

week), even if repeated for up to 5 breeding seasons, did 

not cause widespread impacts to the birds living in mixedconifer forests in Wyoming (Riffell et al. 1996). Such widespread recreation may influence songbirds as community 

diversity and density of common species declined in some 

years. Nearly all songbirds in Southwestern ponderosa 

pine forests were included in this study, but no affects on 

individual species were noted. Therefore, although common species rLay be affected by disturbance in a given 

year, the effects of hiking, nature study, and photography 

are unlikely to be cumulative in ponderosa pine forests 

except where visitor densities are high such as in Grand 

Canyon National Park and large recreation areas. 

Resorts and Recreation Residences - The number of 

resorts, established camps, and recreational residences in 

Southwestern national forests has fluctuated and recently 

declined (Raish et al. this volume). However, the effects 

of the substantial number of resorts and residences that 

remain are similar to the impacts from urbanization, camping, and hiking. The most important results of these developments are habitat loss and fragmentation, supplementing nest predators, habitat structure simplification, 

snag removal, and increased intrusion into surrounding 

forests by residents. Birds near resorts often have breeding disrupted (Lehtonen 1973; Vermeer 1973; Robertson 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Effects of Urbanization and Recreation on Songbirds 

and Flood 1980). Avian diversity decreases and density 

increases as common, widespread species dominate these 

areas (Robertson and Flood 1980). 

Winter Sports and Mechanized Off-road Travel - 

Snowmobiling and off-road vehicles, which are increasing in popularity across the United States (Boyle and 

Samson 1985), have great potential to destroy vegetation, 

alter habitat, and increase wildlife harassment (Berry 1980; 

Boyle and Samson 1985; Cole and Landres 1995). These 

forms of recreation are less common in ponderosa pine 

forests than in higher or lower elevation areas and do not 

appear to significantly affect songbirds in Southwestern 

ponderosa pine forests. 

More important to ponderosa pine forests is ski-area 

development in adjacent, higher elevations. There is an 

increased abundance of scavengers that prey on nests at 

such developments (Watson 1979). More importantly, skiarea development often increases urbanization in ponderosa pine towns. Flagstaff, Showlow, Pinetop, Ruidoso, 

and Taos are all expanding (Raish et al. this volume), partly 

because of increased recreation at nearby ski areas. 

Cumulative Effects of 

Urbanization and Recreation 

Table 1 qualitatively assesses the variety of the potential effects of urbanization and recreation on songbirds in 

the ponderosa pine forest. This assessment summarizes 

the affects discussed in this chapter and are hypotheses rather 

than known influences; many potential affects are unknown 

and many may depend on context. 

The following assumptions were made based on studies conducted elsewhere and species natural history: 1) 

disease negatively affects seed eaters and nectarivores that 

frequent urban feeders; 2) nest predation negatively influences open nesters, especially those in urban areas; 3) 

competition with European starlings negatively affects 

urban cavity nesters; 4) habitat for species that nest in ornamental vegetation or man-made structures improves 

with urbanization, but habitat for natural cavity, canopy, 

shrub, and ground nesters is degraded by urbanization; 

5) urbanization provides increased food for species using 

feeders, lawns, and those able to scavenge refuse; 6) road 

construction favors scavengers and small seed eaters; 7) 

campgrounds are associated with reduced ground and 

shrub coverage, increased nest predation, and supplemental food; 8) hiking, nature study, and photography have 

minor, negative affects on open-nesting species that are 

relatively intolerant of humans; and 9) resorts and recreation residences favor scavengers and birds able to exploit lawns and feeders. 

Few species benefit from urbanization and recreation. 

Large jays, crows, and ravens, human commensals (purple 

martin, brown-headed cowbird, house sparrow, house 

wren, barn swallow, rock dove), and widespread generalists (European starling, Brewer's blackbird) will probably 

increase in ponderosa pine forests as human populations 

continue to increase. Several other species (hummingbirds, 

jays and nutcrackers, chickadees, nuthatches, American 

robin, grosbeaks, juncos, small finches, and chipping sparro&) that exploit some aspect of human activity (primarily food supplements) should remain stable with increasing human populations. The remaining species require 

habitat features that humans disrupt most severely. These 

species (flycatchers, swallows, brown creeper, wrens, bluebirds, Townsend's solitaire, hermit thrush, vireos, warblers, tanagers, song sparrow, and red crossbill) will probably decline in areas of high human use and perhaps 

throughout the ponderosa pine forest if human activities 

continue to increase. 

Research Needs 

Future research should investigate the potential effects 

of urbanization and outdoor recreation in ponderosa pine 

forests. None of the studies reviewed in this chapter directly assessed urbanization and recreation in Southwestern ponderosa pine forests. Nearly every relationship 

hypothesized in table 1 should be tested with designed experiments. Studies of urbanization are especially important 

because affects on birds are significant and human populations are expanding rapidly in ponderosa pine forests. In 

addition, even though many forms of recreation may have 

minor affects on birds, recreation is widespread and increasing in popularity throughout the ponderosa pine forest. 

Investigations should be rigorous, carefully designed 

experiments to establish causal relationships between 

human activity and songbird population viability 

(Gutzwiller 1995; Knight and Cole 1995b). Experiments 

should address the direct and indirect effects of humans 

on songbirds and identify short-term, behavioral and longterm affects on inclusive fitness. Demonstration of human 

impacts on avian fitness is crucial to understand how 

people affect bird populations (Van Horne 1983; Vickery 

et al. 1992). Experiments must be designed to consider 

natural factors, such as weather and food availability, and 

should test the interaction of natural factors with recreation and urbanization on bird populations. An adaptive 

management approach should be used where managers 

implement ideas in a controlled, experimental way and 

researchers test specific management hypotheses. 

Critical evaluation of human influence requires longterm monitoring of abundance, distribution, and fitness 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 97 
Chapter 5 

of uniquely-marked songbirds. Rather than focusing on a European starlings, and house wrens that appear to bensingle species, researchers should monitor all members efit from human activities, should be carefully monitored 

of the avian community simultaneously, perhaps conduct- because they can affect songbirds that may not decline 

ing detailed fitness measurements on representatives of from direct human actions. 

those species most likely to be affected by human activi- Some of the most important research questions concernties. Species, such as American crows, common ravens, ing urbanization impacts are: 1) How do bird communiTable 1. Hypothesized changes in songbird abundance in response to urbanization and recreation in Southwestern ponderosa 

pine forests. Species groups are listed if all members are expected to respond in similar ways; otherwise individual species 

are listed. 

Species 

Recreation 

Urbanization 

Camp1 Hikel Resort1 

Disease Predation Competition Habitat Food Roads Picnic StudylPhoto Residence 

- 

Western kingbird 

Other flycatchers 

Purple martina 

Barn swallow 

Other swallows 

American crow - 

Nuthatches - 

Brown creeper 

House wren 

Other wrens - Bluebirds 

Townsend's solitaire - Hermit thrush - 

American robin - 

Vireos - 

Ground nesting warblers - 

Shrub nesting warblers - 

Canopy nesting warblers - 

Tanagers - 

Grosbeaks - - 

Song sparrow - 

House sparrow - - 

Chipping sparrow - 

Juncos - 

Blackbirds/cowbirds - - 

European starling - 

Red crossbill - 

Other finches - - 

a Natural purple martin nesting sites are reduced with snag removal, but this may be overcompensated for by martin houses placed near urban residences. 

+Affects that may moderately increase a species' abundance or productivity. 

++ Affects that may strongly increase a species' abundance or productivity. 

-Affects that may moderately decrease a species' abundance or productivity. 

-Affects that may strongly decrease a species' abundance or productivity. 

Blank, no affect suspected. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Effects of Urbanization and Recreation on Songbirds 

ties change with increasing urbanization? Standardized 

surveys should be expanded to include urban areas and 

similar rural controls so that changes through time can be 

assessed. Specific comparisons of bird abundance and 

productivity in towns of various size and through time 

would help answer this question. 2) How does a particular type and level of urban development affect birds? Comparisons of bird abundance and productivity among different intensities of urbanization have not been done in 

ponderosa pine forests. In particular, the effects of dispersed housing in the forest, which is growing rapidly, 

should be studied. 3) What types of urban developments 

are most compatible with native songbirds? Research 

about the benefits of landscaping with native plants, using alternative energy sources, and educating homeowners would help identify long-term adjustments that 

government could encourage to minimize human impacts 

on the ponderosa pine avifauna. 4) Do nest predators disproportionately decrease productivity in urban areas relative to rural areas? If so, how does this affect various types 

of birds (open nesters versus cavity nesters, ground versus canopy nesters, social versus solitary species, etc.)? 5) 

How do birds respond to the urban/rural interface? How 

far from urban centers do the effects of urbanization extend into the surrounding forest? How important is the 

impact from house cats and other subsidized predators at 

varying distances from urban sources? Detailed studies 

of radio tagged predators are needed. 

Some of the more important research questions about 

recreation impacts are: 1) What motivates people to pursue various recreational activities? This information will 

better quantify the behavior of people in the forest and 

improve estimation of the amount and projected increase 

in the activity. 2) How do various forms of recreation synergistically affect songbirds? Many forms of recreation 

occur at the same place and at the same or different times, 

yet we know nothing about how they combine to influence songbirds (Gutzwiller 1995). Comparisons of bird 

abundance and productivity across areas with increasing 

multiple recreation use could address this question. 3) 

What influence does Grand Canyon National Park, which 

attracts millions of visitors for a variety of recreational 

pursuits, have on songbirds? This question could be addressed in a broad study comparing bird abundance and 

productivity in and around recreation areas of various size 

in ponderosa pine forests. 4) How long should camps be 

closed to reduce subsidized predator populations? How 

much recovery is needed in camps before sensitive ground 

foragers or cavity nesters return? Assuming that camping affects songbirds as hypothesized, research should be 

conducted to determine how various degrees of camp closure would reduce affects. 5) How can campsites be made 

more beneficial to forest birds and less attractive to human commensals? Research is needed to determine how 

to effectively reduce food supplementation at campgrounds and pack stations, and how to determine if actions, such as increasing habitat diversity or erecting nest 

boxes, would benefit shrub, canopy, and cavity nesters. 

Acknowledgments 

Jddy Burding (Flagstaff Chamber of Commerce), Joyce 

Wachter (U. S. Census Bureau), Colleen Marzluff (S.E.I.), 

and A1 Sanford (New Mexico Institute of Mining and Technology) provided information on economic growth and 

population size in Southwestern cities. Recreation use and 

occupancy data were provided by Britta Morner, Tah Yang, 

Bill Larsen, Lorie Long, and Buddy Stewart of the USDA 

Forest Service. Bird count data were provided by Brett 

Hoover and Keith Pardieck of the National Biological Service. Bill Haneberg provided information on ground water subsidence in New Mexico. Kevin Gutzwiller and Joe 

Ganey helped locate references. Russ Balda supplemented 

the bird count data from Flagstaff. Kevin Gutzwiller, Sallie 

Hejl, and Russ Balda provided manuscript comments. 

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breeding birds in Arizona. Pages 175-182 in R.R. 

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USDA Forest Service, General Technical Report RM-43, 

Fort Collins, CO. USA. 

Anderson, K. 1995. Flagstaff's business growth is positive for 1995. Business Trends 14. 

Anderson, S.H. 1995. Recreational disturbance and wildlife populations. Pages 157-168 in R.L. Knight and K.J. 

Gutzwiller, editors. Wildlife and recreationists: coexistence through management and research. Island Press, 

Washington, DC. USA. 

Andren, H. 1992. Corvid density and nest predation in 

relation to forest fragmentation: a landscape perspective. Ecology 73:794-804. 

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USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 6 

Effects and Interactions of Fire, Logging, and Grazing 

Deborah M. Finch, Joseph L. Ganey, Wang Yong, Rebecca T. Kimball, and Rex Sallabanks 

Introduction 

Logging and livestock grazing are widespread management practices in Southwestern ponderosa pine forests 

that may act either independently or synergistically with 

fire management to influence habitat availability and use, 

reproductive success, and songbird population levels. Fire, 

historically an important natural process in Southwestern ponderosa pine forests, had far-reaching affects on 

forest structure and composition (Moir et al. this volume). 

Because of its influence on forest habitats, and because 

birds respond strongly to habitat structure and composition (MacArthur and MacArthur 1961; Rotenberry 1985), 

historic fires had a powerful impact on forest bird 

communities. 

Contemporary fire suppression and prescribed burning have affected or could affect forest birds and their 

habitat in Southwestern ponderosa pine forests. Fire suppression has disrupted natural fire regimes by removing 

its influence in structuring Southwestern forests (Moir et 

al. this volume). This directly affects structures, stages, 

densities, and landscape patterns of ponderosa pine forests and influences composition and diversity of bird communities at site and landscape levels. Prescribed fire also 

directly alters bird habitat and may be used to create or 

open habitats for some bird species while eliminating or 

reducing habitats needed by others. 

While logging may simulate some aspects of habitat 

alteration caused by natural fire (killing live trees and thinning tree density), current logging practices in ponderosa 

pine typically remove larger trees rather than saplings and 

poles or dead and dying trees (salvage logging). Fire does 

not typically select for tree size and health. Fire-killed trees 

are frequently left standing after a natural fire, providing 

nesting and foraging habitat for many bird species, 

whereas salvage logging deliberately culls trees killed by 

fire, disease, and insect infestation. 

While the interactions between fire and logging complicate our understanding of forested ecosystems and forest use by birds, they are easier to interpret without the 

added effects of grazing. Unfortunately, the relationship 

between livestock grazing and bird habitat use in coniferous forests has been neglected. Consequently, our interpretation of how fire, logging, and their interactions structure forests is uncertain considering the pervasive, subtle 

influence that livestock management has in altering forest habitats. If livestock grazing causes an increased density of young ponderosa pine trees, as some studies show 

(Cooper 1960; Madany and West 1983), then prescribed 

fire and tree thinning may be important management tools 

to restore habitats for birds that use open forests with large, 

old trees or age-structure diversity. 

In this chapter, we summarize current knowledge about 

the effects of fire, logging, and grazing on coniferous forest birds and their habitats. We critically review the results of studies evaluating how these individual factors 

influence bird numbers, species diversity, nesting success, 

and habitat use in ponderosa pine forests. Documented 

and potential interactions among fire, fire exclusion, logging, livestock grazing, and range management are discussed in relation to habitat structure, succession, and 

avian use. Finally, we outline some areas where further 

research is needed to better understand the effects of fire, 

logging, grazing, and their interactions on birds and their 

habitats in Southwestern ponderosa pine forests. 

Fire 

Effects of Fire on Forest Birds 

Fire can affect forest birds directly or indirectly, positively or negatively. A number of factors determine how 

fire influences particular bird species including: 1) fire extent and intensity; 2) temporal scale at which effects are 

evaluated; 3) the particular life history of the species involved; and 4) whether salvage logging follows the fire. 

Fire can affect birds directly by causing mortality or reduced reproduction (Patton and Gordon 1995; Rotenberry 

et al. 1995). Mortality due to fire is generally considered 

minor for adult birds (Rotenberry et al. 1995). However, 

mortality of nestlings or fledglings or reduced reproduction due to reductions in food supply is possible if fires 

occur during the breeding season (Patton and Gordon 

1995). 

Fires typically affect birds indirectly through habitat 

modification, changes in food supply, or changes in abundance of competitors and/or predators (Rotenberry et al. 

1995). The effects of fire on habitat structure, food resources, and floristic composition may be especially important because many birds respond strongly to these 

habitat features (MacArthur and MacArthur 1961; Koplin 

1969; Lovejoy 1974; Tomoff 1974; Power 1975; Willson 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 6 

1974; James and Wamer 1982; Rotenberry 1985; Terrill 

1990). 

Many authors have reviewed the effects of fire on forest birds (Bendell 1974; Hutto et al. 1992; Dobkin 1994; 

Hejl 1994; James and Hess 1994; Hejl et al. 1995; Patton 

and Gordon 1995; Rotenberry et al. 1995; Ganey et al. 1996). 

Several recent reviewers (Hutto et al. 1992; Dobkin 1994; 

Hejl 1994; Ganey et al. 1996) have concluded that the literature on fire and birds suffers from serious methodological problems. Most studies on the effects of fire on birds 

were opportunistic rather than planned, were restricted 

in spatial and temporal scale, and lacked sufficient replication to show general patterns (Dobkin 1994;, Hejl1994; 

Hutto 1995). Many studies comparing bird communities 

between burned and unburned areas relied on composite 

statistics, such as total bird abundance or species richness, 

rather than examining the response patterns of individual 

species. These composite measures may hide rather than 

reveal patterns where individual species respond in an 

opposite manner (Mannan et al. 1984; Rotenberry 1985; 

Hejl et al. 1995; Hutto 1995). Most studies focused on the 

effects of fire on breeding bird communities, ignoring 

nonbreeding bird communities (but see Blake 1982). Finally, few studies examined demographic parameters 

(Hejl 1994). Without information on parameters, such as 

nest success and survival rates of birds occupying burned 

areas, we cannot assess how well such areas provide for 

the needs of the species occurring there. These problems 

limit our ability to draw inferences and, in some studies, 

the inferences drawn are unsupported by the data. Despite these problems, some generalizations are possible. 

First, the effect of fire on birds and their habitat varies 

Third, life history characteristics also influence the response of particular bird species to fire. Cavity-nesting 

birds, timber-drilling birds, granivores, and some flycatchers generally respond positively to burns in the short term 

because of increased nesting substrates and/or food supplies (Blackford 1955; Stoddard 1963; Koplin 1969; Bock 

and Lynch 1970; Kilgore 1971; Lowe et al. 1978; Overturf 

1979; Taylor and Barmore 1980; Granholm 1982; Harris 

1982; Raphael et al. 1987; Hejl1994; Hejl et al. 1995; Hutto 

1995; Sallabanks 1995; Caton 1996; Hitchcox 1996). Some 

species may even require intense burns for long-term 

population maintenance (black-backed woodpecker) 

(Hutto 1995). In contrast, foliage-gleaning insectivores 

generally respond negatively to fire due to decreased foraging substrate (Bock and Lynch 1970; Roppe and Hein 

1978; Overturf 1979; Blake 1982; Granholm 1982; 

Sallabanks 1995). Response patterns may vary even within 

guilds (Skinner 1989; Hutto 1995; Mannan et al. 1984; 

Rotenberry 1985). For this reason, summary statistics, such 

as species diversity or total abundance, which are commonly reported, should be used to compare pre- and postfire bird communities. Diversity and abundance may be 

similar between these communities, but species composition is often strikingly different (Hutto 1995; Sallabanks 

1995). 

Fourth, the response of birds or bird communities to 

fire may also vary depending on whether salvage logging 

follows the fire. As mentioned, snags created by fire can 

provide nest and foraging sites. Removal of some or all of 

these snags eliminates or reduces the benefits they provide (Moeur and Guthrie 1984; Hutto 1995; Hitchcox 1996). 

with the extent and intensity of the fire. Large fires generally affect more habitat and therefore more birds than do Studies on the Effects of Fire on Ponderosa 

small fires, and hot fires alter forest structure more than Pine Birds 

cool fires. A stand-replacing fire may result in many or 

most of the species present before the fire being replaced 

by a new species (Hutto 1995). In contrast, cool understory burns may have little affect on species composition 

(Horton and Mannan 1988). How individual species respond to fire may depend on the size of the fire. 

Second, fire effects also vary across temporal scales. 

Intense burns initially produce numerous snags for cavity-nesting birds (Hejl et al. 1995; Hutto 1995; Caton 1996; 

Hitchcox 1996) and abundant food resources for timberdrilling species such as woodpeckers (Koplin 1969; Wauer 

and Johnson 1984; Hutto 1995). However, habitat suitability for woodpeckers will decline over time as these snags 

fall and food resources decrease (Koplin 1969; Bock et al. 

1978; Raphael and Morrison 1987; Raphael et al. 1987; 

Johnson and Wauer 1996). Although large, intense burns 

greatly alter bird habitat in the short-term, they may be 

necessary for long-term maintenance of natural forest succession patterns of some forest types (Hejl et al. 1995; Hutto 

1995) or for habitat diversity in others. 

Less is known about the effects of fire on birds in ponderosa pine forests than about the effects of fire on forest 

birds in general. We located only 7 studies about the effects of fire on birds in ponderosa pine forests, and only 5 

of these were conducted in Southwestern ponderosa pine 

forests. An additional 2 studies were conducted in pineoak forests in southeastern Arizona. Because these forests 

contain ponderosa pine, they have been included; however, their applicability to pure Southwestern ponderosa 

pine forests is unknown. 

Most studies about the effect of fire on birds in ponderosa pine forest contained methodological problems (table 

1). In addition, some studies (Bock and Bock 1983; Horton 

and Mannan 1988) focused on prescribed fire while others (Lowe et al. 1978; Overturf 1979; Blake 1982;Aulenbach 

and OrShea-Stone 1983; Wauer and Johnson 1984; Johnson 

and Wauer 1996) focused on wildfires. This makes it difficult to compare these studies because different types of 

fires should have different affects on vegetation and on 

birds. The situation is further complicated because some 

1 04 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Effects and Interactions of Fire, Logging, and Grazing 

Table 1. Descriptive characteristics of studies of the effects of fire on birds in ponderosa pine and Southwestern pine-oak 

forests. 

Reference 

Forest 

tY Pea Locationb 

Number Fire Fire 

of plotsC typed sizee Limitationsf 

Lowe et al. 

(1 978) 

Overturf 

(1 979) 

Blake 

(1 982) 

Aulenbach and 

O'Shea-Stone 

(1 983) 

Bock and 

Bock (1 983) 

Horton and 

Mannan (1 988) 

Johnsonand 

Wauer (1 996); 

Johnson (1 984) 

ecdotal; no replication; 

>graphic effect possibly c 

h fire effects 

M-L No replication; some or 

all sites logged; sample reas crossed 

burn boundaries 

No replication; all burned 

y confused with logging effects 

, few observations for most 

4B,4C P S, M Not in the Southwest; Bock 

(2) data averaged across woodland and 

nnah habitats 

250% PP; data averaged Wauer and 

across forest types within transects 

a Forest types: PO = pine-oak; PP = ponderosa pine; M = mixture (mixed-conifer, ponderosa pinelmixed-conifer, ponderosa pine, ponderosa pinelpinyon-juniper, and 

pinyon-juniper). 

Location: SE = southeast; N = northern; C = central; AZ = Arizona; NM = New Mexico; CO = Colorado; SD = South Dakota. 

Plots: 0 = burned; C = unburned control. Number of separate burns studied shown in parentheses. 

Fire type: W = wildfire; P = prescribed fire. 

Fire size (after Heinselman 1981): S = small (<40 ha); M = medium (41-405 ha); L= large (406-4050 ha); VL = very large (> 4050 ha). 

Aspects of study design that may limit inferences drawn about the effects of fire on birds in Southwestern ponderosa pine forest. 

studies focused on small and others on large fires, and 

because several studies examined birds in areas that were 

salvage-logged following fire, confounding logging effects 

with fire effects. Methods differed between studies, and 

studies were conducted at varying times following fires. 

All of the above problems limit our ability to draw inferences from these studies. Careful examination of study 

designs, sampling methods, and results also suggests that 

some of the inferences drawn by the authors are unsupported. We review these studies below in chronological 

order and briefly discuss methods, important results, and 

limitations of those results. 

Marshall (1963) noted parallel variation in fire regime, 

habitat conditions, and bird communities between the 

mountains of southern Arizona and northern Mexico 

(Sonora and Chihuahua). Although his observations related to Madrean pine-oak forests dominated by Chihuahua and Apache pines, the natural fire regime was similar to that in ponderosa pine (Ful6 and Covington 1995). 

Marshall's observations may be relevant to Southwestern 

ponderosa pine forests. 

Wildfires were suppressed as quickly as possible in Arizona, but most were allowed to bum in Mexico (Marshall 

1963). Consequently, forests and woodlands in Arizona were 

denser than similar types in Mexico. Several bird species 

common to brush or dense forest were more abundant in 

Arizona than in Mexico including the ash-throated flycatcher, 

blue-gray gnatcatcher, black-throated gray warbler, Scott's 

oriole, and spotted towhee. In contrast, several species preferring open forest conditions were either more abundant in 

Mexico or occurred at higher elevations. Marshall (1963) attributed this pattern to the existence of open forest conditions at higher elevations in Mexico. Examples of these species included the violet-green swallow, Cassin's kingbird, 

curve-billed thrasher, canyon towhee, purple martin, chipping sparrow, and both eastern and western bluebirds. Although these observations are interesting, no quantitative 

data were presented on differences in bird communities 

among areas. Further, we cannot rule out the possibility that 

the observed variation in bird communities was related to 

geographic or climatic variation or to other unknown factors rather than only to differences in fire policy. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 6 

Lowe et al. (1978) sampled birds in 1 year on 4 sites in 

northern Arizona ponderosa pine forests that had undergone stand-replacing fires at various times, and also on 

one unburned plot. Their sampling occurred either 1,3,7, 

or 20 years post-fire, depending on the particular site. They 

reported dramatic increases in populations of ground-foraging birds immediately after the fires, followed by a 

gradual decline as canopy cover increased. Timber-drilling birds also increased in burned areas, apparently in 

response to increased numbers of wood-boring insects. 

Timber-gleaning or bark-foraging birds decreased following fire, with populations remaining depressed for up to 

20 years. Tree-foliage-searching birds increased immediately after fire, then declined dramatically over time. Flycatcher populations peaked approximately 7 years after 

fire. 

Lowe et al. (1978) assumed that the observed variation 

in bird communities across sites was due to the length 

time after fire, rather than to site differences. This assumption may be unjustified (see Hejl and Woods 1991) and is 

impossible to test because different post-fire periods were 

not replicated. Also, at least some and probably all of the 

burned sites were salvage logged, making it difficult to 

distinguish fire effects from logging effects. Finally, areas 

on which birds were sampled crossed the boundaries between burned and unburned areas. 

Overturf (1979) compared breeding bird communities 

on an unburned site with those on 3 sites burned by wildfire and salvage-logged on the Coconino National Forest, 

northern Arizona. One of the 3 burns studied was also 

studied by Lowe et al. (1978). Species composition varied 

between burned and unburned sites. Bird communities 

on burned sites were dominated by ground-foraging birds 

(chipping sparrow, lark sparrow, dark-eyed junco, greentailed towhee, western bluebird, northern flicker, and 

house wren) (Overturf 1979). Some birds using the shrubsapling and canopy layers were lost from the burned sites 

(Grace's warbler, mountain chickadee, solitary vireo, 

Steller's jay, pygmy nuthatch, pine siskin, and mourning 

dove) (Overturf 1979). Large snags on burned areas were 

used for nesting by numerous woodpeckers, nuthatches, 

bluebirds, and house wrens. Woodpeckers, especially 

hairy and three-toed woodpeckers, foraged on large and 

small snags. Although the unburned site contained the 

greatest richness and abundance of birds, the 4 sites together housed more species than any single site. Overturf 

(1979) concluded that, although avian diversity might be 

reduced on an individual burn, the patchiness caused by 

burns across the landscape might enhance avian diversity. Similar to Lowe et al. (1978), Overturf (1979) studied 

birds on sites that were salvage-logged following fire, 

which makes it impossible to separate fire effects from 

logging effects. 

Blake (1982) studied the effects of a large wildfire and 

logging on nonbreeding bird communities on the Prescott 

National Forest, Arizona. He established 6 study plots, 3 

in the burned area and 3 in unburned areas. Each burned 

plot was paired with an unburned plot based on 3 levels 

of logging activity. Plots were either unlogged, selectivelylogged, or clear cut. Some species of birds were observed 

only on either burned or unburned sites. More of these 

were restricted to unburned than to burned sites. Foliagegleaning insectivores were more abundant on unburned 

sites than on burned sites, whereas aerial insectivores (flycatchers hnd swallows) were more abundant on burned 

sites. Hairy woodpeckers were most abundant on burned 

sites, but bark-gleaning birds were most abundant on 

unburned sites. 

Blake (1982) concluded that habitat openness was a prfmary determinant of nonbreeding bird community structure, and that habitat alterations caused by fire and logging had similar affects on the nonbreeding avian 

community. This conclusion was largely based on similarities in summary statistics such as species diversity and 

total bird abundance. Examination of his table 2 suggests 

that there were differences in community composition 

between burned and unburned sites within logging treatments. Blake also lacked replication within cells of his 

experimental design and studied birds primarily in areas 

that were logged (4 of 6 plots). Although inferences from 

this study on the effects of fire on forest birds are limited, 

this study is one of the best of its kind in the Southwest. 

Aulenbach and O'Shea-Stone (1983) compared bird 

communities between a small (2 ha) area burned by wildfire and a similar control site in ponderosa pine forest in 

Colorado. Pygmy and white-breasted nuthatches, downy 

woodpeckers, and mountain chickadees were observed 

only on the unburned site. Red-breasted nuthatches, chipping sparrows, yellow-rumped warblers, spotted towhees, 

and northern flickers were seen only on the burned site. 

The American robin, Steller's jay, and dark-eyed junco 

were seen on both plots but were most common on the 

burned plot. This study is particularly problematic. Study 

sites were not replicated and were separated by only 60 

m, making their treatment as independent sampling units 

questionable given the high mobility of many birds. The 

total number of individuals observed per site in all censuses was >2 for only 4 species (Aulenbach and O'SheaStone 1983), suggesting that sample sizes for individual 

species were inadequate to support conclusions on their 

response to fire. For these reasons, it is impossible to draw 

any meaningful inference from this study. 

Bock and Bock (1983) studied the response of breeding 

birds to cool-season prescribed burning in ponderosa pine 

forest in South Dakota. Populations of breeding birds were 

monitored for 2 years following the fires. Six species 

(mountain bluebird, solitary vireo, yellow-rumped warbler, western tanager, dark-eyed junco, and chipping sparrow) were more abundant on the burned areas than on 

unburned areas in at least 1 year (Bock and Bock 1983). 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Effects and Interactions of Fire, Logging, and Grazing 

Table 2. Response patterns of selected birds to fire in ponderosa pine or Southwestern pine-oak forest. Only species with an 

apparent trend are listed. 

Species Locationa Seasonb ResponseC Referencesd 

Mourning dove More common on burned plots 

Hairy woodpecker More common on burned plots 

C AZ N B More common on burned plots 

Declined on burned plots 

Peclined on burned plots 

Declined on burned plots 

re common on burned plots 

mon on burned plots 

on burned plots 

n burned plots 

Pygmy nuthatch ore common on unburned plots 

White-breasted More common on unburned plots 

Nuthatch Red-breasted Nuthatch SD B Declined on burned plots in 1 of 2 yrs 

Brown creeper N AZ B More common on unburned plots 

House wren N NM B Increased on burned plots 

American robin SD B More common on burned plots in 1 yr, 

on unburned the other yr 

Hermit thrush N NM B Declined on burned plots 

Mountain bluebird S D B More common on burned plots in 1 yr 

N NM B Increased on burned plots 

C AZ NB More common on burned plots 

N NM B Increased on burned plots 

N B More common on unburned plots 

B More common on burned plots in 1 yr 

Virginia's warbler B Declined on burned plots 

Grace's warbler B More common on unburned plots 

B Declined on burned plots 

Yellow-rumped Warbler B More common on burned plots in 1 yr 

Western tanager B More common on burned plots in 1 yr 

Dark-eyed junco B More common on burned plots in 1 yr 

Chipping sparrow B More common on burned plots in 1 yr 

B More common on burned plots 

White-crowned Sparrow C AZ N B More common on burned plots 

Green-tailed B More common on burned plots 

Towhee Spotted towhee N NM B Increased on burned plots 

a Location: SE = southeast; N = northern; C = central; AZ = Arizona; NM = New Mexico; SD = South Dakota. 

Season: B = breeding; NB = nonbreeding. 

Only Bock and Bock (1983) and Horton and Mannan (1988) tested for differences in abundance of individual species between treatments. Results from other studies 

are based on data examination or statements in text. Note that increases or decreases may vary across temporal scale. 

References: 1 = Lowe et al. (1978); 2 = Blake (1982); 3 = Horton and Mannan (1988); 4 = Johnson and Wauer (1996); 5 = Bock and Bock (1983); 6 = Overturf (1979). 

The red-breasted nuthatch was more abundant on the 

unburned areas in 1 year, but not in the other year. The 

American robin was more abundant on burned plots in 

the first year, and on unburned plots in the second year. 

This study avoided many of the pitfalls discussed previously. Results were averaged across woodland and savannah habitat. However, the applicability of results obtained 

in South Dakota woodlands and savannahs to Southwestern ponderosa pine forest is unknown. 

Horton and Mannan (1988) studied the effects of prescribed burning on cavity-nesting birds in pine-oak forest in the Santa Catalina Mountains, southern Arizona. 

They sampled birds on 6 plots in 6 separate stands; 3 were 

burned and 3 were unburned. The prescribed burn resulted in a moderately-intense surface fire that remained 

within prescription. Few differences were observed in bird 

populations before and after fire. Only northern flickers 

and violet-green swallows declined in abundance in 

burned stands and only mountain chickadees increased. 

Horton and Mannan (1988) concluded that the observed 

declines in northern flickers and violet-green swallows 

were not due to a shortage of nest sites because post-fire 

densities of suitable snags (snags >50 cm dbh [diameter 

at breast height] in particular decay classes) exceeded 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 107 
Chapter 6 

densities theoretically required to support pre-fire numbers of cavity-nesting birds. 

The plots studied by Horton and Mannan (1988) were 

dominated by ponderosa pine but also contained 2 species of evergreen oak, Mexican white pine, and Douglasfir. They were not pure Southwestern ponderosa pine forests and the results may not be applicable to pure 

ponderosa pine forest. 

Patton and Gordon (1995) briefly summarized the effects of fire on individual bird species, many of which inhabit ponderosa pine forest. This summary was based on 

evidence in the scientific literature, supplemented by personal experience ("in many cases the relationships are intuitive or self-evident from experience;" Patton and Gordon 1995). We will not repeat this summary by species, 

but instead refer to Appendix B in Patton and Gordon 

(1995). Many of the references used in evaluating the effects of fire on birds were from habitat types other than ponderosa pine forest or from geographic areas outside of the 

Southwestern United States. Their conclusions may not be 

relevant to birds in Southwestern ponderosa pine forests. 

Johnson and Wauer (1996; see also Wauer and Johnson 

1984) sampled birds before and after the 1977 La Mesa 

fire in the Jemez Mountains, northern New Mexico. Birds 

were sampled in 1977 (pre-fire), 1978,1979,1981,1983, and 

1991 on 4 transects; 3 burned and 1 unburned. Only 1 of 

these transects consisted of 250 percent ponderosa pine 

forests; the others were dominated by mixed-conifer forest, ponderosa pine/mixed-conifer forest, ponderosa 

pine/pinyon-juniper forest, and/or pinyon-juniper woodland (Johnson and Wauer 1996). 

Many changes in community composition were noted 

through time. The most pronounced change was a marked 

increase in woodpeckers. Some flycatchers also increased 

following fire, but the ash-throated flycatcher declined on 

the transect dominated by ponderosa pine. Mountain 

chickadees, hermit thrush, Grace's warblers, and Virginia's 

warblers also declined, whereas house wrens, western 

bluebirds, mountain bluebirds, and spotted towhees all 

increased on this transect at some point in time (Johnson 

and Wauer 1996). 

This study and Wauer and Johnson (1984) are the only 

ones that directly examined the composition of bird communities on particular sites over time; they therefore provide some intriguing results on succession in bird communities. However, two factors limit the strength of this 

data set for evaluating effects of fire on birds in Southwestern ponderosa pine forest. The first is that only 1 year of prefire data on bird abundance and composition is available. 

Consequently, it is impossible to estimate the annual variability in bird abundance before the fire on any transect. This 

would not be such a large problem if strong comparisons 

could be made between the burned transects and the unburned transect. The marked differences in vegetation types 

across transects weaken such comparisons. 

Effects of Fire on Important Habitat 

Components 

Because little is known about the effects of fire on birds 

in Southwestern ponderosa pine forest, we reviewed current knowledge regarding the effects of fire on important 

habitat components for forest birds. Although many habitat components may be important, we focus on snags, logs, 

and oalfrs, which are particularly relevant to evaluating 

the effects of fire on birds in Southwestern ponderosa pine 

forests. We summarize below the available information 

on the potential importance of these components to forest birds and discuss the results of studies on the effects 

of fire on these habitat components. 

Snags 

The importance of snags to ponderosa pine bird communities is well documented (Balda 1975; Scott 1978,1979; 

Cunningham et al. 1980). Snags are preferentially used 

for foraging and nesting by many birds inhabiting Southwestern ponderosa pine forests (Balda 1975; Cunningham 

et al. 1980). Large snags are particularly important to bird 

communities. Nesting use is concentrated in large snags 

(Scott 1978; Cunningham et al. 1980; Raphael and White 

1984; Horton and Mannan 1988; Caton 1996; Hitchcox 

1996), and they also tend to stand longer than smaller 

snags (Raphael et al. 1987; Morrison and Raphael 1993). 

Snags appear to have a finite period during which they 

are heavily used for foraging and nesting. In northern 

Arizona, most nesting occurred in snags that were 5 to 20 

years old, whereas most foraging occurred on snags that 

were 1 to 5 years old (Cunningham et al. 1980). This was 

presumably because although insects colonized these 

snags rapidly, their numbers declined over time (Cunningham et al. 1980). Thus, snags in this area are most 

useful to birds for a 20-year period following death. 

Fire can create, modify, or destroy snags depending on 

its behavior and local conditions. Intense burns can create numerous snags that provide foraging and nesting 

resources for many birds (Blackford 1955; Koplin 1969; 

Overturf 1979; Taylor and Barmore 1980; Wauer and 

Johnson 1984; Raphael et al. 1987; Hutto 1995; Sallabanks 

1995; Caton 1996; Hitchcox 1996; Johnson and Wauer 

1996). Granholm (1982), however, noted that snags recently killed by fire in the Sierra Nevada Mountains lacked 

the soft heartwood required for nest excavation, whereas 

many suitable snags were consumed by fire. Thus, both 

prescribed and natural fires can negatively or positively 

affect availability of suitable snags for cavity-nesting birds. 

Gaines et al. (1958) quantified the effects of 2 prescribed 

burns on snags in Southwestern ponderosa pine forest. 

Snags >30 cm dbh declined by 56 percent in the first burn 

and increased by 175 percent in a second burn. However, 

this large increase in snag abundance was in an area containing only 1 snag/ha before burning (Gaines et al. 1958). 

108 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Effects and Interactions of Fire, Logging, and Grazing 

Horton and Mannan (1988) studied the effects of prescribed fire on snags in a Southwestern pine-oak forest 

dominated by ponderosa pine. They observed a net 45 

percent decrease in snags following prescribed burning. 

Proportional snag loss was greatest in the size (>50 cm 

dbh) and decay (111 and IV) classes containing the most 

nest cavities. Horton and Mannan (1988) attributed much 

of the snag loss to the amount and type of woody debris 

at the base of the snag; snags surrounded by large amounts 

of loose, relatively undecayed debris were likely to burn. 

Many small (<I5 cm dbh) snags were created in these 

burns, which may provide foraging opportunities but are 

unlikely to be used for nesting (Balda 1975; Scott 1978; 

Cunningham et al. 1980; Horton and Mannan 1988). 

Gordon (1996) quantified the effects of 3 prescribed 

burns on snags in northern Arizona ponderosa pine forests. She considered all snags with dbh 220.3 cm, height 

22.4 m, and <90 percent of the surface charred as suitable 

for use by nesting birds. Of 61 suitable snags tagged on 

experimental plots, 32 remained suitable for use by nesting birds following the burns and 12 could not be relocated. Thus, the proportion of snags lost or rendered unsuitable ranged from 35 to 48 percent, depending on 

whether or not snags that could not be relocated were 

actually burned. Constructing fire lines around snags influenced their fate; 50 percent of unlined snags versus 27 

percent of lined snags were unsuitable after the fire. Many 

snags that were unsuitable for nesting were partially 

charred. These had fallen and broken into large pieces becoming part of the log component. Although fire can have 

detrimental affects on pre-burn snags, it can also cause 

pre-burn live trees to die and become snags. 

Logs 

Downed logs can also provide foraging opportunities 

for forest birds (Horton and Mannan 1988; Bullet al. 1995), 

but generally their importance to communities of forest 

birds is not well documented. Horton and Mannan (1988) 

observed signs of foraging activity before burning by cavity-nesting birds on 37 percent of ponderosa pine logs in 

their study area. Foraging activity was more common on 

logs with sapwood; 43 percent of logs with sapwood 

showed signs of foraging activity versus 28 percent of logs 

without sapwood. Following prescribed fire, log number 

and volume declined by 42 and 56 percent, respectively. 

Number and proportion of logs with sapwood declined by 

62 and 16 percent, respectively (Horton and Mannan 1988). 

Foraging activity was not quantified in post-fire plots. 

Gaines et al. (1958) also reported on effects of prescribed 

burning on logs. Total weight of large logs (defined as 

230.5 cm maximum diameter) declined by 63 and 74 percent on the 2 burns they sampled (Gaines et al. 1958). Total weight of small logs (5 to 30 cm maximum diameter) 

declined by 62 percent in one burn and increased by 83 

percent in another. 

Gordon (1996) tagged 62 logs before prescribed burning on 3 experimental plots. Using a modification of USDA 

Forest Service guidelines (no citation given in Gordon 

1996), she defined all logs with diameter (unspecified 

point of measurement) 220.3 cm, length 22.4 m, and <90 

percent of the surface charred as suitable. Gordon relocated 59 of these following burning; 43 (69 to 72 percent 

depending on whether logs that could not be relocated actually burned) were classed as unsuitable following the fire. 

Of these, 77 percent suffered severe charring and reduction 

in diameter and 23 percent were completely consumed. 

Oaks 

Oaks (and possibly other hardwoods) also provide important resources for birds in Southwestern ponderosa 

pine forests. For example, Szaro and Balda (1979a) noted 

that several species of birds foraged extensively in Gambel 

oak in northern Arizona pine forests. Patterns of tree-species selection varied among bird species and with silviculture type, but some forest birds (yellow-rumped warbler, Grace's warbler, and white-breasted nuthatch) used 

oak foliage more than expected considering its contribution to the total foliage volume (Szaro and Balda 1979a). 

Brawn and Balda (1988a) also commented on the importance of Gambel oak to bird communities. They noted 

that oaks could provide nest sites for secondary cavity 

nesters and important food resources, and they observed 

that densities of insectivorous birds were higher on plots 

with oaks than on similar plots containing only pines. 

Both Gambel and evergreen oaks, including Emory, 

Arizona white, and silverleaf, also provide important resources for birds in other pine-oak forest types in the 

Southwestern United States (Marshall 1957; Balda 1967; 

Block et al. 1992). Some or all of these species resprout 

after fire (Babb 1992; Caprio and Zwolinski 1992; 1995; 

Barton 1995), and they can rapidly recolonize burned areas. Generally, however, the effects of fire on these species are not well understood, particularly in a ponderosa 

pine forest. 

Many oak species resprout after fire and may be able to 

quickly recolonize sites following burns even if topkill 

occurs (Barton 1995; Caprio and Zwolinski 1995). Some 

species of oaks may need more sunlight than they would 

get in the shade of closed-canopy forests. Therefore, although fire may reduce the number of large oaks in the 

short-term, in the long-term, fire-created openings could 

be beneficial (or even necessary) in maintaining oak as a 

landscape component (but see Barton 1995). 

Conclusion 

The literature on the effects of fire on bird communities 

in Southwestern ponderosa pine forest is replete with 

problems. Available evidence about such results is anecdotal (Marshall 1963), without replication (Lowe et al. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 109 
Chapter 6 

1978; Overturf 1979; Blake 1982; Aulenbach and O'SheaStone 1983; Wauer and Johnson 1984; Johnson and Wauer 

1996), has limited replication (Bock and Bock 1983; Horton 

and Mannan 1988), or confounds the effects of fire with 

those of logging (Lowe et al. 1978; Overturf 1979; Blake 

1982). The picture is further clouded because some studies evaluated effects of low-intensity prescribed burns 

(Bock and Bock 1983; Horton and Mannan 1988), whereas 

others studied areas subjected to intense wildfire (Lowe 

et al. 1978; Overturf 1979; Blake 1982; Wauer and Johnson 

1984; Johnson and Wauer 1996). Some studies were conducted in areas outside the Southwestern United States 

(Aulenbach and O'Shea-Stone 1983; Bock and Bock 1983) 

or in forest types related but not equivalent to ponderosa 

pine forest (Marshall 1963; Horton and Mannan 1988). 

Only 1 study (Johnson and Wauer 1996; see also Wauer 

and Johnson 1984) actually monitored bird communities 

over time on a burned area, and only 2 studies (Bock and 

Bock 1983; Horton and Mannan 1988) provided statistical 

comparisons of abundances of individual species of birds 

between burned and unburned areas. Many authors 

evaluated results primarily in terms of summary statistics, such as diversity or total abundance, which can mask 

large variation in community composition. 

All of these factors limit the inferences that can be drawn 

about the effects of fire on birds in Southwestern ponderosa pine forests and, in some cases, cause us to question 

inferences drawn by the original authors. Despite these 

problems, however, there are some relatively consistent 

results when trends are evaluated about guilds or individual species. For example, large stand-replacing fires 

radically alter vegetation structure and bird community 

composition. Although the effects of cool prescribed burns 

are less extreme than those of intense wildfires, they follow the same trend. In general, granivores, timber-drilling birds, and some aerial insectivores increase after fires, 

whereas timber- and foliage-gleaning birds generally decrease (table 2). Even within these guilds, there is sometimes variation. For example, ash-throated flycatchers responded opposite of other flycatchers in the area studied 

by Johnson and Wauer (1996). Finally, community composition will change over time. For example, granivores such as 

dark-eyed junco, chipping sparrow, white-crowned sparrow, 

and towhees often increase significantly shortly after fire 

(table 2), followed by woodpeckers, which often peak in the 

first decade following fire, then gradually decline. Birds more 

closely tied to foliage availability (hermit thmsh, solitary 

vireo; table 2) generally decline immediately after fire, then 

begin recovering as foliage volume increases in subsequent 

years. The effects of fire on birds is best understood by considering the type of fire, the amount of time that has elapsed 

since the fire, the response patterns of individual species, 

and the extent of post-fire salvage logging. 

The effects of fire on important habitat components also 

depends on fire type. Intense bums may create different 

size snags, but these may not be immediately suitable for 

excavation of nesting cavities (Granholm 1982) and many 

will not last long (Cunningham et al. 1980; Raphael et al. 

1987; Morrison and Raphael 1993). Prescribed bums may 

also create snags. When such burns are low intensity, however, they are unlikely to kill many large trees but may 

destroy large snags, which results in a decrease in availability of the large snags preferentially used by forest birds 

(Horton,and Mannan 1988). Intense wildfires and lowerintensity prescribed burns probably decrease the amount 

of downed logs (Gaines et al. 1958; Horton and Mannan 

1988; Gordon 1996). This decrease may be alleviated in 

subsequent years as fire-killed snags fall, but these logs 

may not contain the sapwood preferred by foraging birds 

(Horton and Mannan 1988). Finally, the effects of fire on 

oaks in ponderosa pine forests is unclear. 

Because fire is an important natural process in Southwestern ponderosa pine forests (Moir et al. this volume), 

communities of forest birds are well-adapted to cope with 

the natural fire regime in these forests. Disruption of that 

fire regime, however, along with grazing, timber harvest, 

and fuelwood cutting, has caused pronounced structural 

changes in these forests. As a result, wildfires today may 

burn more intensely and over larger areas than historical 

fires (Moir et al. this volume), which could have significant negative affects on communities of forest birds and 

their habitat. Currently, these effects are impossible to quantify, but they may be particularly important where past fire 

suppression efforts have been most successful. 

Numerous authors have called for restoring fire as a 

natural process in ponderosa pine forests (Covington and 

Moore 1994a; Sackett et al. 1994; Arno et al. 1995; Fule 

and Covington 1995). Fire will continue to operate in these 

systems in spite of our attempts to exclude it (Boucher 

and Moody 1996). Given current forest conditions, restoring natural fire regimes will require substantial increases 

in prescribed burning to reduce fuel loads (Harrington 

and Sackett 1990; Covington and Moore 1994a; Sackett et 

al. 1994; Arno et al. 1995). Limited evidence on the effects 

of prescribed fire on forest birds and their habitat suggests that important habitat components of forest birds 

may be affected by prescribed fire, at least in the short 

term. To avoid large-scale loss of important habitat components, special techniques, including thinning dense stands 

and creating fire lines for snags and logs, may be required to 

reintroduce fire into areas where it has been excluded. 

Logging 

The following section evaluates the relationship of logging to habitat use by songbirds occupying Southwestem ponderosa pine forests. A review of historic and con110 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Effects and Interactions of Fire, Logging, and Grazing 

temporary silviculture is provided by Raish et al. (this 

volume). Today's forests have been altered by fire exclusion, a decrease in the frequency of natural fires due to 

diminished fuel availability, and a reduction of herbaceous 

fuels caused by grazing and trampling by cattle and sheep 

in the 1880s and 1890s (Weaver 1951; Cooper 1960; 

Covington and Moore 1994a,b). Fire exclusion has been 

proposed as a primary reason for the development of overstocked forests in the Southwest (Covington and Moore 

1994a,b). Covington and Moore (1994b) report that 

presettlement tree density was about 56 trees/ha in contrast to the current density of about 2,100 trees/ha, which 

is mostly small-diameter trees. 

Logging contributes about 18 percent to growing stock 

mortality in the Southwest (Raish et al. this volume). Interpreting changes in stocking rates and volume of ponderosa pine over time is complicated by logging effects. 

The general rule for historic logging was to harvest the 

most accessible and commercially valuable trees (Scurlock 

and Finch this volume), which contributed to the decline 

of large trees. In the late 1980s, ponderosa pine accounted 

for about 73 percent of the lumber cut by sawmills in New 

Mexico and about 91 percent of the timber harvested in 

Arizona (Van Hooser et al. 1993). Sawtimber accounted 

for 90 percent of the total ponderosa pine cut in both states 

(Van Hooser et al. 1993). Between 1962 and 1986, sawtimber stands decreased by 10 percent in Arizona, while small 

trees (seedling, poletimber, sapling) increased by 3 times 

over the amount present in 1962 (Spencer 1966; Conner et 

al. 1990; Johnson 1995). While stocking volume of sawtimber with dbh < 43.2 cm increased between 1962 and 

1986, volume of sawtimber with dbh 143.2 cm decreased 

during the same period (Raish et al. this volume). 

In addition, even-aged management commonly practiced in the Southwest creates an age-class distribution of 

forest habitats that differs from forests without timber 

harvest. Depending on rotation age, natural disturbance 

frequency, and moisture regime, forests harvested using 

even-aged management could have more or less early successional forest rather than natural landscapes (Thompson et al. 1995). In the Southwest, contemporary ponderosa pine forests contain more midsuccessional growth 

than do unharvested forests that have a greater uniformity 

of habitat patch sizes and distributions (Raish et al. this volume). Given these changes in tree size, density, and sera1 

stage distribution over time, it seems clear that logging and 

other types of silviculture have affected the availability, structure, age, and composition of stands at the local stand level 

and at the landscape and regional levels. Such changes 

have potentially affected the number and distribution of 

bird populations using ponderosa pine habitats. Unfortunately, few studies have evaluated effects of landscape-level 

or large-scale changes on Southwestern ponderosa pine birds 

(Rich and Mehlhop this volume). Further experimental research on this topic is needed (Block et al. this volume). 

Bird Use of Successional Stages Created by 

Logging 

Documented changes in the structure, density, age, and 

diversity of Southwestern ponderosa pine forests could 

potentially affect the breeding, wintering, and migration 

success of birds, and hence, the population status of bird 

species. Successional changes in habitat are produced by 

natyral events, such as fire, or by management such as 

logging or prescribed burns. These effects could be positive or negative, long- or short-term, and local or regional. 

In this section, we review and evaluate studies that compare bird response to successional habitats created by logging. Most published studies of bird responses to logging 

of Southwestern ponderosa pine have been descriptive, 

lacking the rigor of experimental research with pretreatment periods and replicated study sites and treatments. 

Southwestern ponderosa pine forests evolve through 

the following generalized successional stages: 1) grassforb, shrub-seedling (0 to 10 years); 2) pole-sapling (11 to 

40 years); 3) young forest (41 to 100 years); 4) mature forest (101 to 200 years); and 5) old growth (201+ years). 

Canopy volume, understory productivity, and plant and 

animal diversity varies among these successional stages. 

Forest management, especially silvicultural, alters the direction and pace of forest succession so that it that may be 

accelerated or shortened or stages may be bypassed. Several bird species inhabiting ponderosa pine forest feed and 

nest in mature and old-growth successional stages (Hejl 

1994; Hall et al. this volume). In the past, emphasis on 

wood production of Southwestern ponderosa pine frequently determined silvicultural practices that favored establishment of the most economically valuable trees, emphasized rapid growth, and shortened harvest time. 

Ecologically, the result was a truncated successional pattern in which early and late stages were shortened or eliminated (Edgerton and Thomas 1978). Multi-storied mature 

and old-growth ponderosa pine forests provide feeding 

and nesting habitats for many bird species; several are 

considered specialized and adapted only to those environments. Mid-sera1 stages, such as pole-sapling and 

young forest, which are emphasized by intensive timber 

management, could significantly alter avian species composition and relative abundance because they lack the 

structural diversity qualities of older stands. 

Meslow (1978) suggested that wood-production practices alter forest habitats by: 1) shortening the grass-forb 

and shrub stage; 2) creating an even-aged monoculture; 

3) eliminating snags; and 4) eliminating old-growth. Evenaged regeneration methods almost completely remove 

previous stands, which can lead to a complete turnover 

in breeding birds. Even-aged silviculture within potential Mexican spotted owl (Strix occidentalis lucida) habitats 

in ponderosa pine forests tends to simplify stand structure and establishes stands without the key habitat charUSDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 6 

acteristics used by owls (USDI Fish and Wildlife Service 

1995). Selection cutting maintains a specific tree-diameter 

distribution through periodic removal of selected trees; 

this results in less change to vegetation structure and bird 

communities within stands than even-aged management. 

Selectively-cut stands retain much of the mature forestbird community and provide habitats for some species 

that use the ground-shrub-sapling layer (USDI Fish and 

Wildlife Service 1995). However, selection cutting ultimately tends to homogenize the landscape by reducing 

or eliminating stand differences, thereby reducing horizontal patchiness across the landscape. 

Reviews of Bird Use of Logged Western 

Forests 

Hejl (1994) summarized information on the effects of 

human-induced environmental change on avian populations in Western North America during the past 100 years. 

She reported that 13 species (three-toed woodpecker, 

black-capped chickadee, mountain chickadee, redbreasted nuthatch, winter wren, ruby-crowned kinglet, 

Swainson's thrush, varied thrush, solitary vireo, Townsend's warbler, evening grosbeak) were always less abundant in recent clearcuts than in uncut forest. In contrast, 

the mountain bluebird was always more abundant in recent clearcuts. Differences were less dramatic between 

partially-logged forests and unlogged forests. Pygmy 

nuthatch and pine grosbeak were always less abundant 

in partially-logged forests than in unlogged forests. Calliope hummingbird was always more abundant in partially-logged forests. In general, forest species were found 

less often in clearcuts, and species that frequent open forests or habitats were found more often in clearcuts. Resident species tended to decrease after any kind of harvesting, whereas only about half of the migrants decreased. 

In contrast, almost all the species that increased after partial cutting or soon after clearcutting were migrants, and 

most of the species using recent clearcuts were short-distance migrants. 

To evaluate relationships between Southwestern bird 

populations and logged forests, we extracted information 

on ponderosa pine forests of the Southwest from a comprehensive review of bird use of logged and unlogged 

conifer forests of the Rocky Mountains (Hejl et al. 1995). 

For their analysis of widespread bird population responses, Hejl et al. (1995) compared population responses 

of bird species inhabiting uncut forests to those observed 

using 4 vegetation classes: 1) low shrub clearcuts (from 

grass-forb to small shrub stage; generally 0 to10 years old); 

2) tall shrub clearcuts (including tall shrubs and seedlings; 

generally 11 to 20 years old); 3) pole sapling clearcuts (generally 21 to 40 years old); and 4) partial cuts (any cutting 

treatment other than clearcutting). Their inclusion of studies from the Southwest provides an index about how bird 

populations and silviculture in the Southwest compared 

to other geographical areas. While clearcutting is common 

in many forests of the Rocky Mountains, partial cuts are 

common in Southwestern ponderosa pine; therefore, we 

are cautious about interpreting abstracted results. Even 

so, the following analysis has merit because it compares 

bird population responses along a successional spectrum 

of stages that can be found in the Southwest. 

Hejl et al. (1995) scored each bird species as less abundant (-I), similarly abundant (0), or more abundant (+I) 

at each logged and unlogged site cited in the literature. 

The potential relationship between each harvest class and 

each bird species was determined by calculating the average score over all such studies. An index of 1.0 indicated that every study reported more birds in treated than 

in untreated areas. An index of -1.0 indicated that every 

study reported more birds in the untreated than treated 

areas. An index of 0.0 indicated that either a species had 

similar abundances in treated and untreated areas in every study, or that no obvious trend was detected across 

studies. Researchers had sufficient data on 40 bird species known to use Southwestern ponderosa pine forests 

to evaluate responses to partial or clearcut treatments. Of 

these, 11 (red-breasted nuthatch, ruby-crowned kinglet, 

western tanager, three-toed woodpecker, white-breasted 

nuthatch, hermit thrush, orange-crowned warbler, western wood-pewee, and common nighthawk) were consistently less abundant (score = < 0) in all stages of clearcuts 

than in unlogged areas (table 3). Six species (mountain 

chickadee, red-breasted nuthatch, ruby-crowned kinglet, 

three-toed woodpecker, solitary vireo, white-breasted 

nuthatch) were always less abundant (score = -1) in recent, low-shrub clearcuts than in untreated sites. An additional 17 bird species were frequently less abundant (0 

< score > -1) in low-shrub clearcuts (table 3). All permanent resident species were less abundant in low-shrub 

clearcuts. In addition, pygmy nuthatch was always less 

abundant (score = -1) in partially-logged areas than in 

untreated areas. 

In contrast, 9 migrant species (chipping sparrow, broadtailed hummingbird, dark-eyed junco, mourning dove, 

white-crowned sparrow, Townsend's solitaire, dusky flycatcher, mountain bluebird, and rock wren) were generally more abundant (score > 0) in low-shrub clearcuts than 

in unlogged areas although this trend was inconsistent 

among studies for some species. The rock wren was more 

numerous in partially logged areas than in unlogged areas in all studies (score = 1). In addition, Steller's jay, warbling vireo, black-headed grosbeak, northern flicker, redraped sapsucker, fox sparrow, American robin, chipping 

sparrow, Townsend's solitaire, broad-tailed hummingbird, 

dark-eyed junco, dusky flycatcher, and mountain bluebird were generally more abundant (scored > 0) in either 

tall-shrub and/or pole-sapling clearcuts than in untreated 

areas. 

USDA Forest Service Gen.Tech. Rep. RM-GTR-292. 1997 
Effects and Interactions of Fire, Logging, and Grazing 

Table 3. Abundance of bird species that occur in clearcut, partially cut, and uncut Southwestern ponderosa pine forest. A 

species was more abundant (+I), less abundant (-I), or similarly abundant (0) in treated versus untreated areas. Values in 

the table are averages of these scores over all studies on which the species was recorded. Species are ranked in ascending 

in order from -1.00 based on low-shrub clearcut column. Sample sizes are in parentheses (analyses were only performed on 

the species with sample size 2 3). Table modified from Hejl et a/. 1995. 

NTMB Low 

statusb shrub 

Clearcuts 

Tall Pole Partially 

shrub sapling cut 

Mountain chickadee -1 .OO 

-1 .oo 

Brown creeper -1 .OO 

Golden-crowned kinglet -1 .OO 

Ruby-crowned kinglet -1 .OO 

Three-toed woodpecker 

0.33 

White-breasted nutha 

Pygmy nuthatch 

Western tanager -1 .OO 

Hermit thrush 

Steller's jay 0.33 

Warbling vireo 1 .OO 

Yellow-rumped warbler -0.50 

Black-headed grosbeak 0.40 

Violet-green swall 

Pine siskin 0.00 

Western wood-pewee 

House wren 0.00 

-0.33 

-0.33 

0.67 

0.67 

Red-naped sapsucker -0.14 (7) 0.00 

American robin 0.50 

Cassin's finch -0.20 

Cordilleran flycatc 

Williamson's saps 

Chipping sparrow 0.67 

Western bluebird 

Olive-sided flycatch 0.25 

1 .oo 

1 .oo 

Townsend's sol 0.25 

1 .oo 

Mountain bluebird 0.90 (10) 1 .OO 

Rock wren B 

a Species list is based on Szaro and Balda (1979), Franzreb and Ohmart (1978), Scott and Gottfried (1983), Blake (1982), and Franzreb (1978). 

As designated by the Partners in Flight preliminary list:A = long-distance migrant species, those that breed in North America and spend their nonbreeding period primarily south 

of the United States; B = short-distance migrant species, those that breed and winter extensively in North America; C = migrants whose breeding range is primarily south of the 

United StatedMexican border and enter the United States along the Rio Grande Valley or where the Mexican highlands extend across the United States border (these 

populations largely vacate the United States during the winter months) R = permanent resident species that primarily have overlapping breeding and nonbreeding areas. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 113 
Chapter 6 

Studies in Southwestern Ponderosa Pine 

Forests 

The most extensive series of studies about bird responses to ponderosa pine logging in the Southwest were 

conducted at the Beaver Creek Watershed, central Arizona 

(Szaro and Balda 1979a, 1979b, 1986; Gaud et al. 1986; 

Brawn and Balda 1988a, 1988b). Szaro and Balda (1979a) 

compared species diversity and relative abundance of 

birds among different timber management practices. 

These practices were: 1) clearcut (removal of all commercial woody vegetation), 2) severely thin (removal of most 

of the timber stock); 3) strip cut (alternate "level" strips 

were thinned to improve production); and 4) silviculturally cut (mature and old trees were selectively cut) (see 

Szaro and Balda [1979a] for more information about treatments). Because clearcuts and strip cuts are now uncommon in the Southwest, the Beaver Creek Watershed study 

is a historical study rather than a current standard. In addition, habitat characteristics differed among plots within 

treatments, making it difficult to eliminate the possibility 

that plot variation was due to plot differences rather than 

silviculture. 

Compared to the control plot, bird abundance and species diversity was lower on the clearcut and severelythinned plots but higher on strip-cut and silviculturallycut plots (table 4). Rock wren, American robin, dark-eyed 

junco, spotted towhee, northern flicker, and mountain 

bluebird used the clearcut plot, but only rock wren and 

spotted towhee were favored by clearcutting. On the other 

hand, removal of some mature and old ponderosa pines 

using strip cuts and silvicultural cuts favored house wren, 

solitary vireo, yellow-rumped warbler, Grace's warbler, 

rock wren, American robin, chipping sparrow, whitebreasted nuthatch, western wood-pewee, and western 

bluebird. The uncut control plot had higher abundances 

of pygmy nuthatch, red-faced warbler, hermit thrush, 

western flycatcher, and violet-green swallow. Four foraging guilds (pickers and gleaners, ground feeders, hammerers and tearers, and aerial feeders) were either favored 

or not affected by strip-cut and silvicultural-cut methods. 

Three nest guilds (cavity and depression nesters, foliage 

nesters, and ground nesters) were positively affected by 

the silvicultural cut. 

Szaro and Balda (1986) concluded that openings generated by logging could result in major shifts in local availability of habitats for a given bird species and might be a 

primary factor in the selection of breeding sites. Those 

species that typically used more open habitats (rock wren, 

American robin, western wood-pewee, and western bluebird) were most abundant on either medium or heavy cuts. 

Those species that prefer dense foliage (western flycatcher, 

pygmy nuthatch, red-faced warbler, hermit thrush, and 

black-headed grosbeak) were less abundant in more modified habitats. Of the 15 species found on all forested plots, 

33 percent (chipping sparrow, western bluebird, broadtailed hummingbird, Grace's warbler, and dark-eyed 

junco) had highest population densities on treated plots, 

suggesting preference for a more open canopy. 

Szaro and Balda (1986) predicted that inter- and intraspecific competition for food resources should be 

greater on heavy and medium treated sites where the foliage/bird pair was lower than on the lightly cut and untreateq sites. However, an examination of the insect food 

base on the sites indicated that mean bird density was not 

correlated with either insect numbers or biomass on either relative or absolute bases. They concluded that the 

foliage available on these sites was not being fully used, 

and that other factor(s) (territoriality, lack of suitable nesting sites, non-insect food supply, lack of openings or other 

habitat configurations) might limit ponderosa pine bird 

communities on sites with dense foliage. Brawn et al. 

(1987) further suggested that interspecific competition for 

food during the breeding season was not important in 

structuring ponderosa pine bird communities. 

Franzreb (1978) and Franzreb and Ohmart (1978) studied the effects of moderately heavy overstory removal in 

a mixed-conifer forest in the White Mountains of Arizona. 

Avian species richness was equal on the treated area and 

an adjacent unharvested comparison area; however, overall abundance was significantly higher on the latter. 

Franzreb and Ohmart (1978) also found no relationship 

between avian diversity and measures of vertical habitat 

complexity. Bird abundances on treated and untreated 

areas varied among species and guilds, probably reflecting differential responses to availability of foraging and 

nesting substrates. Thirteen species, primarily bark/foliage foragers and cup-nesters, were more abundant on the 

unharvested area, whereas 10 species of aerial and ground 

foragers were more abundant on the treated portion. 

Franzreb and Ohrnart suggested that numerical reductions 

of some species on treated stands could be related to more 

restricted or more specialized vegetation preferences. 

Scott and Gottfried (1983) examined the combined effects of several management prescriptions (individual 

selection, group selection, and patch cutting) on avian 

communities in a mixed-conifer forest of Arizona. Species richness increased by 25 percent on the harvested area 

but decreased by 7 percent on an adjacent, unharvested 

area. Post-treatment avian abundance decreased 12 and 3 

percent on the 2 areas, respectively. Only 1 species showed 

a significant decrease in density on the treated area. These 

results were considerably different than those reported 

by Franzreb and Ohmart (1978); this was attributed by 

Scott and Gottfried (1983) to heavier timber harvest in their 

study area. However, given the absence of replicated treatment sites in both studies, we do not believe that strong 

inferences can be made about treatment effects for either 

study. In addition, results from mixed-conifer forests may 

differ from those in pure ponderosa pine. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Effects and Interactions of Fire, Logging, and Grazing 

Table 4. Effect of silvlcultural treatment on avian abundance and diversity in Southwestern ponderosa pine forests. Numbers 

are average breeding pairs/40 ha. Table was modified from Szaro and Balda (1979a). 

Species Clearcut Thinned Strip cut Silv cut Control 

Mountain chickadee 

Pygmy nuthatch 

House wren 

Solitary vireo 

Yellow-ru 

Grace's \F 

Red-facet 

mped warbler 

varbler 

d warbler 

Western tanager 

Hepatic tanager 

Mourning dove 3.5 1 2 

Rock wren 

American r 

Hermit thru 

Dark-eyed junco 1.8 7.5 9.5 16.7 13 

Spotted towh 6.4 

Ch~pping spa 

Northern flick 0.5 

Acorn woodpecker 1 

3 

4 

8.5 

Black-headed 2.5 

1 2 

- 

catcher 

be 

~od pewee 

Broad-tailed humminabird 6.5 

Western fly 

Say's phoe 

Western wc 

Violet-green swallow 

Western bluebird 

Ground feeders 

Hammerers and tearers 16.5 

Aerial f~ 

Cavity 2 

Foliage 

Ground nesters 6.8 14.3 

seders 0.3 17.3 3d 

wid depressio 0.8 0 3' 

nesters 6.8 8.8 64 

Mannan and Siegel (1988) and Siegel (1989) sampled avian 

communities in managed stands and in 3 types of old-growth 

(open, dense, and minimum) in northern Arizona. Managed 

stands were even-aged and dominated by densely-spaced, 

younger (80-year-old) trees. Open old-growth stands had 

numerous large (> 50 cm dbh) trees with an open understory and were chosen to represent presettlement conditions. 

Dense old-growth stands had an overstory of large trees and 

a well-developed understory of smaller trees; a common 

condition in remaining old-growth ponderosa pine in Arizona. Minimum old-growth stands had received previous 

light harvest but met old-growth standards set by the USDA 

Forest Service. AU 4 stand types differed significantly in habitat stmcture, although the old-growth stands often contained 

patches resembling other stages. Avian species richness was 

similar across all 3 old-growth conditions (41 to 47 species) 

but lower in managed stands (32 to 34 species). The highest 

avian abundance was in dense old-growth, whereas the lowest was in managed stands. Within the 3 old-growth types, 

several species varied considerably in their abundance. This 

was attributed to the availability of mesic microenvironments, openings, and other habitat requisites. 

USDA Forest Service Gen.Tech. Rep. RM-GTR-292. 1997 115 
Chapter 6 

Keller (1992) conducted a survey of breeding birds in 

several ponderosa pine stand types in north central Arizona. He found that bird species diversity and density 

were greatest in stands containing L 14 yellow pines/acre 

and lowest in pure stands of pole timber. Keller suggested 

that avian species richness and abundance might be linked 

to the availability of large, mature ponderosa pines. 

Rosenstock (1996) studied habitat relationships of passerine breeding birds in ponderosa pine and pine-oak forests of northern Arizona from 1993-1995. He sampled 23 

study sites representing a broad habitat gradient from 

intensively-managed stands with large openings to 

unmanaged stands with dense thickets of young trees 

under a mature pine overstory. Rosenstock found that 

breeding birds showed strong responses to stand structure at both the community and species levels. Species 

composition and bird numbers differed based on pine 

canopy configuration, tree size and density, and the density and physical characteristics of Gambel oaks and snags. 

Five species (pygmy nuthatch, violet-green swallow, Cordilleran flycatcher, house wren, and brown creeper) were 

positively correlated with high canopy density, low 

canopy patchiness, and vertical diversity. Five species 

(Townsend's solitaire, white-breasted nuthatch, hermit 

thrush, hairy woodpecker, and brown-headed cowbird) 

were also correlated with low horizontal patchiness and/ 

or vertical diversity, but not with canopy density. Six species (chipping sparrow, hairy woodpecker, house wren, 

pine siskin, pygmy nuthatch, and violet-green swallow) 

were positively correlated with the coefficient of variation in pine size (dbh); given that 5 of these 7 species nest 

in holes or under bark, this relationship may be related to 

nesting preferences. 

Nonbreeding Studies 

Few studies have investigated the influence of logging 

on nonbreeding bird communities in Southwestern ponderosa pine forests. Hagar (1960) found that fall and winter densities on logged areas in California were 2 to 3 times 

higher than those on unlogged areas; high values were 

due to large numbers of granivorous birds. Blake (1982) 

reported that granivores in Southwestern ponderosa pine 

forests were more abundant than other guilds on clearcut 

areas in fall and winter. Most granivores left by spring, 

reducing overall abundance levels; following their departure, bird assemblages were dominated by insectivorous 

species. Blake (1982) also reported that logging produced 

an open canopy that was correlated with increased numbers of flycatchers and aerial and ground-feeding insectivores. He concluded that responses to logging were similar for both nonbreeding-season (spring, fall, and winter) 

and breeding-season bird communities and suggested that 

the extent of habitat modification might be more influential than the precise type of alteration. As mentioned, however, caution must be used in interpreting Blake's results 

because the study design was confounded by interactions 

with fire and by lack of replication of study plots. 

Studies of Nest Site Use in Relation to 

Silviculture 

Few demographic studies of songbird communities in 

Southyestern ponderosa pine forests have been conducted. Based on a study of cavity-nesting birds using a 

mixed ponderosa pine forest on the Mogollon Rim, central Arizona, Li and Martin (1991) reported that live and, 

more commonly, dead aspens (Populus trernuloides) were 

used in 88 percent of cavity nest sites, although aspens 

constituted only 12 percent of the trees. Preference for aspen may be related to ease of excavation of this soft wood, 

which is often decayed even in live trees. Aspen suckers 

frequently sprout in cleared mixed forests after logging 

or fires. The amount of large aspens in the area studied 

by Li and Martin (1991) may be explained by early succession of aspens after extensive conifer logging years ago. 

Aspen numbers and acreage in fire-excluded forests 

have gradually declined in the Southwest as conifers have 

replaced them (USDA Forest Service 1994). According to 

the USDA Forest Service (1993), the acreage of aspendominated forests in Arizona and New Mexico has decreased from 486,000 acres in 1962 to 263,000 acres in 1986. 

Continued loss of aspens due to fire suppression and conifer succession may escalate competition for favored nest 

sites by cavity-nesting birds and may result in decreased 

populations of cavity-nesting birds. Logging and fire in 

forests mixed with aspens may improve nesting habitat 

for cavity-nesting birds by allowing aspen to regenerate. 

However, logging may also reduce the quantity of ponderosa pine snags available for nest sites by reducing the 

number of live mature pine trees that eventually die and 

become snags. 

Brawn and Balda (1988b) suggested that the breeding 

density of cavity-nesting birds was nest-site limited for 

species that were locally common and relied on dead trees 

for nest sites in ponderosa pine forests of northern Arizona. Martin (1988) found that predation rates in Arizona 

ponderosa pine forests were lower at nest sites with higher 

foliage density at nest height and proposed that breeding 

birds selected habitats based in part on the availability of 

nest sites that minimize risk of nest predation. Because 

variation in foliage density in nesting layers influences 

the reproductive outcome of some open-cup nesting songbird species of ponderosa pine forests, for example, hermit thrush (Martin and Roper 1988), silvicultural alteration of foliage density could influence nesting success. 

The above studies suggest that silviculture alters availability of desirable nest sites and may influence populations of bird species that place nests in specialized ways. 

Our personal observations suggest that demographic reUSDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Effects and Interactions of Fire, Logging, and Grazing 

sponses to silviculture are likely to differ greatly among 

species and treatments. Tom Martin and colleagues are 

studying the reproductive success of songbirds in Southwestern forests along the Mogollon Rim, and their publications should help to clarify interactions between habitat features and reproductive success. In the mean time, further 

speculation pertaining to the relationship between silviculture and nesting success of songbirds in ponderosa pine 

forest is unwarranted until specific hypotheses are tested. 

(Bock and Webb 1984). Assuming this is true in coniferous forests as well, it is necessary to understand how grazing affects habitat structure and composition to assess the 

possible effects of grazing in ponderosa pine forests on 

songbird populations. Unfortunately, it may not be possible to assess the impact of grazing on ponderosa pine 

songbirds by extrapolating from studies in other habitats, 

as birds respond differently to grazing in different grassland habitats (Saab et al. 1995). 

Landscapes Grazers 

As discussed earlier, even-aged silviculture affects the 

spatial distribution of different-aged stands, while unevenaged treatments tend to reduce differences among stands. 

Stand size determines the size of habitat patches created 

by regeneration cuts and is usually in the range of 5 to 20 

ha on public lands. Natural disturbances and openings 

are more frequent at small scales than at large scales, but 

these vary widely in magnitude and size. Even-aged management tends to exclude very small and very large 

patches, resulting in artificial uniformity of habitat patch 

sizes and distributions. The juxtaposition of different-aged 

stands may result in increased amounts of edge in the forest, which may affect the reproductive success and abundance of songbirds (see review by Thompson et al. 1995). 

Logging clearly modifies ponderosa pine landscapes in 

the Southwest. How altered landscapes ultimately affect 

bird populations and assemblages is discussed in more 

detail by Rich and Mehlhop (this volume). 

Grazing and Range Management 

Practices 

There have been many studies assessing the impact of 

grazing on bird populations in the West but few that focus on ponderosa pine forests (for reviews, see Bock et al. 

1993; Fleischner 1994; Saab et al. 1995). Livestock grazing 

in Southwestern ponderosa pine forests has been common 

since the 19th century (Cooper 1960; Dutton 1953; Scurlock 

and Finch this volume), so it is likely that habitat changes 

due to grazing exist in most forested areas of the Southwest. These habitat changes may alter species abundances 

and composition in avian and other wildlife communities. While the need to study the impacts of grazing in 

coniferous forests on wildlife populations has long been 

recognized (Clary 1975), no studies have yet assessed how 

grazing in Western coniferous forests might affect bird populations (Bock et al. 1993; Dobkin 1994; Saab et al. 1995). 

Studies in grasslands have concluded that birds do not 

respond to grazing per se but rather to habitat changes 

Several domesticated species graze in Southwestern 

ponderosa pine forests. Cattle currently are the most common livestock species; sheep populations have greatly 

decreased since the turn of the century (Cooper 1960). Big 

game, such as elk (Cervus canadensis) and mule deer 

(Odocoileus virginianus) are also frequently present. Game 

species probably have similar impacts on plant growth 

and composition as do livestock (Barnes et al. 1991). Supporting this idea, several studies in a variety of forest ecosystems in the Western United States have indicated that 

there is overlap between the diets of cattle, deer, and elk 

(MacCracken and Hansen 1981; Skovlin et al. 1976; 

Thilenius and Hungerford 1967). The degree to which big 

game species alter the habitat depends on population 

sizes, but they can have measurable impacts on the quantity and composition of plant species when population 

sizes are large. In a Douglas-fir/ponderosa pine forest in 

Oregon, there was no statistical difference in herbaceous 

species between plots grazed and not grazed by big game; 

but presence of game species did lead to a statistical difference in browse species (Krueger and Winward 1974). 

Earlier in the century, the mule deer population on the 

Kaibab Plateau in northern Arizona greatly increased causing damage to the habitat by overgrazing (Mitchell and 

Freeman 1993; Rasmussen 1941). All grazing species, not 

just domestic livestock, may affect ponderosa pine habitats in ways that could influence songbird populations. 

Grazing Systems 

The mere presence of livestock does not mean that longterm habitat destruction is occurring (Clary 1987). Instead, 

the degree to which grazing affects the habitat, and hence 

the birds using that habitat, depends on several factors. 

These include the: 1) number of animals grazing in an area; 

2) time of grazing; and 3) grazing system used. Greater 

habitat changes occur as grazing intensity increases in 

ponderosa pine habitats outside the Southwest (Johnson 

1956; Skovlin et al. 1976), and this is likely to occur in the 

Southwest as well. Grazing during the spring and early 

summer may directly decrease the reproductive success 

of breeding birds through destruction or disturbance of 

nests on the ground or in low shrubs. Grazing during other 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 117 
Chapter 6 

seasons can indirectly affect bird communities through 

habitat changes. 

Little is known about the effects of different grazing 

systems in Western coniferous forests (Saab et al. 1995). 

In ponderosa pine forests in the Blue Mountains of Oregon and Washington, deferred rotation grazing increased 

vegetation cover in open grassland areas but not in forested areas, as compared with season-long grazing 

(Skovlin et al. 1976). Pearson et al. (1971) used a 3-pasture 

rest rotation system in a ponderosa pine forest in Arizona. 

Since cattle tended to avoid mature grasses, concentrating instead on succulent growth, the timing was adjusted 

so that no plant species was overgrazed. This system was 

effective in achieving good weight gain in cattle while 

maintaining a diverse balance of plant species. Some grazing systems may be less detrimental to riparian zones than 

others. Marlow and Pogacnik (1985) found that cattle had 

a lower impact on stream banks when soil moisture was 

high, while Clary and Webster (1989) suggested that spring 

grazing may have the lowest impact on riparian zones. The 

results of studies comparing different grazing systems in 

other habitats have been variable (Dwyer et al. 1984) and 

probably no single system will give the same results in all 

areas. Hence, even if more data were available from ponderosa pine forests, it may be difficult to predict what effect 

specific grazing practices will have on avian habitat. 

Effects of Grazing on Birds 

As stated, the primary effects of grazing on songbirds 

should be caused by habitat alterations. At least 2 species 

of ponderosa pine birds, the buff-breasted flycatcher and 

the western bluebird, have exhibited population declines 

that were attributed to habitat overgrazing (DeSante and 

George 1994). This speculative conclusion was derived 

from a review of historical information rather than from 

an analysis involving a replicated experiment. Taylor and 

Littlefield (1986) reported that when grazing levels were 

reduced in the Malheur National Wildlife Refuge in Oregon, populations of the willow flycatcher and yellow 

warbler increased. 

Changes in the Understory 

Grazing can reduce the volume of grasses and, to a lesser 

extent, the forbs and shrubs, which form much of the understory vegetation in ponderosa pine habitats of the 

Southwest (Koehler et al. 1989; Madany and West 1983) 

and other Western regions (Johnson 1956; Laudenslayer 

et al. 1989; Rummell1951; Skovlin et al. 1976; Zimmerman 

and Neuenschwander 1984). Some of the more common 

species that may decrease in abundance are mountain 

muhly (Mulzlenbergia montana), muttongrass (Poa fendleriana), Arizona fescue (Festuca arizonica), squirreltail (Sitanion kystrix) and blue gramma (Bouteloua gracilis). Common 

shrub species affected by grazing include servicebeny (Amelanchier spp.), bear-berry (Arctostaphylos spp.), (Holodiscus 

discolor), willow (Salix spp.), and spiraea (Spiraea spp.). 

In addition to reducing the understory volume, grazing also alters the composition and structure of understory plant communities (Arnold 1950; Clary 1975; 

Johnson 1956; Knopf 1996; Madany and West 1983; 

Rummell 1951; Skovlin et al. 1976; Zimmerman and 

Neuenschwander 1984). This can involve changes in the 

abundance of different species, as plants preferred by grazers are reduced and those tolerant of grazing become 

dominant. Grazing also reduces the number of plant species present. 

In addition to the direct reduction of understory vegetation due to grazing, grazing can also indirectly decrease 

understory vegetation. Growth of understory vegetation 

is lower in areas of high canopy cover (Arnold 1950; Moir 

1966; Severson 1987). Since increases in tree density occur 

in response to grazing (see below), grazed areas may have 

greater canopy cover, leading to a further reduction in the 

understory vegetation. 

Importance of Understory Structure to Birds - Several 

studies have examined the relationship between the quantity and diversity of vegetation and how this affects bird 

densities. In a variety of different habitats, there is a positive relationship between the volume and structural diversity of the vegetation and the density of birds in the 

area (Bull and Skovlin 1982; Karr 1968; Martin 1984; Mills 

et al. 1991; Tomoff 1974; Verner and Larson 1989; Willson 

1974). While no studies have assessed these relationships 

in Southwestern ponderosa pine forests, understory diversity in a coniferous forest in Utah was positively related to bird community diversity (Wine 1976). Species 

composition of the vegetation is also important in avian 

community composition in grassland communities 

(Rotenberry 1985). This suggests that replacement of a 

plant species, even if the structure of the plant is the same, 

may affect bird species using the habitat. 

Some ponderosa pine bird species are only found in 

areas with dense understory vegetation. These species, 

which include dusky flycatcher (Sedgwick 1993), Bewick's 

wren (DeGraaf and Rappole 1995), solitary vireo (DeGraaf 

and Rappole 1995), orange-crowned warbler (Sogge et al. 

1994), MacGillivrayfs warbler (Pitocchelli 1995), Virginia's 

warbler (DeGraaf and Rappole 1995) and spotted towhee 

(DeGraaf and Rappole 1995), are likely to decrease in 

abundance if the volume of understory vegetation is reduced. Since grazing alters species composition, reduces 

the number of species in the understory, and decreases 

the volume of the understory, changes in the abundances, 

compositions, and richness of songbird species may occur in areas of Southwestern ponderosa pine forests that 

are heavily grazed. Such changes may involve a decrease 

in abundance or the disappearance of species preferring 

dense vegetation. However, species that prefer a more 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Effects and Interactions of Fire, Logging, and Grazing 

open understory may then colonize the area or increase 

in abundance. 

Nesting in Relation to Understory Changes - Species 

that nest on the ground or in shrubs may be negatively 

affected by changes in the understory, as sites suitable for 

nesting may be eliminated for some species (Knopf 1996). 

Spruce/ fir forests in the Rocky Mountains generally have 

only 1 species of ground nester (dark-eyed junco); the low 

number of ground-nesting species has been attributed to 

the lack of understory cover necessary for other avian 

ground nesting species (Smith 1980). Therefore, ground 

and shrub nesting species, such as those listed in table 5, 

may suffer reduced reproductive success and may decrease in abundance when the understory vegetation necessary for structural support, cover, and protection of the 

nest has been reduced or altered. 

The avian species in table 5 are nesting generalists; 

multiple species of grasses and shrubs can provide suitable nesting sites. Therefore, as long as sufficient volume 

in the understory remains, a loss of 1 or a few understory 

species may not affect nesting habitat for those species. 

We suggest that even if all plant species are retained in 

grazed areas, the amount or suitability of nesting habitat 

will be reduced if the abundance or volume of each plant 

species decreases. To test this hypothesis, experiments that 

test the effects of shrub or grass removal on nesting success of understory-nesting birds are needed. 

Foraging in Relation to Understory Changes - Structure and composition of the understory is also important 

for foraging. Green vegetation is relatively unimportant 

for ponderosa pine birds; no bird species heavily depends 

on greens (Ehrlich et al. 1988). However, seeds and berries, many of which are produced by understory vegetation (see list of shrubs above), are important for many bird 

species. When grazing changes the quantity and composition of the understory, the amount of available food for 

some bird species also changes. 

Because most ponderosa pine birds that use understory 

plants are generalized feeders, they are less likely to depend on specific plant species than on plant structure and 

abundance (Rotenberry 1985). The species most likely to 

be affected by changes in plant composition are broadtailed and rufous hummingbirds, since these species are 

specialized to forage on suitably shaped flowers, such as 

columbine (Aquilegia spp.), scarlet gilia (Ipomopsis aggregate), and penstemon (Penstemon spp.). Although hummingbirds may be adapted to forage on specific flower 

shapes, they will also forage on a variety of other plant 

species (Carder and Calder 1992; Calder 1993). Penstemon 

spp! increased in a grazed ponderosa pine forest in Arizona (Arnold 1950); thus, grazing of understory plants is 

not necessarily correlated with reductions of hummingbird food. No studies have specifically addressed whether 

variation in seed and berry production or quantity and 

species richness of flowering or fruiting plants affects bird 

species that forage on understory substrates. 

Insects are an important food source for songbird species, as they are the primary food for offspring. Abundance 

and species composition of insects may be affected by 

changes in the understory vegetation, as many insect species depend on specific plants to provide food and oviposition sites. Brawn et al. (1987) concluded that competition for food among breeding insectivorous birds was 

absent in Arizona ponderosa pine forests, even though 

densities of breeding birds had been increased through 

habitat manipulation. Further studies are needed to determine whether abundance and species composition of 

arthropods in Southwestern ponderosa pine forests vary 

in relation to grazing patterns, and whether such variation can affect species composition or bird reproduction. 

The structure and density of the vegetation may be more 

important when foraging for insects than the number or 

species of insects available, as has been found in an Eastern deciduous forest (Robinson and Holmes 1984). Foliage gleaners will probably be most affected by changes in 

the structure of the understory, though some species are capable of adapting foraging strategies in response to changes 

in the vegetative structure (Robinson and Holmes 1984). 

Many avian species forage, at least in part, on the 

ground. As more bare ground becomes available due to a 

Table 5. Bird species in ponderosa pine forests that nest primarily on the ground or in low shrubs. 

Species 

Dusky flycatcher 

Hermit thrush 

Orange-crowned warbler 

Virginia's warbler 

MacGillivray's warbler 

Red-faced warbler 

Green-tailed towhee 

Dark-eyed junco 

Song sparrow 

Nest Locality 

Shrub 

Shrub 

Ground 

Ground 

Shrub 

Ground 

Shrub 

Ground 

Shrub 

Reference 

Sedgwick 1993 

Martin 1993 

Martin 1993; Sogge et al. 1994 

Martin 1993 

Martin 1993; Pitocchelli 1995 

Martin 1993; Martin and Barber 1995 

Martin 1993 

Martin 1993 

Kern et al. 1993 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 119 
Chapter 6 

reduction in the grasses and other understory vegetation, 

foraging may become more efficient for some ground feeders, although conversely, there may be less to forage on. 

Those species that frequently forage on bare ground, such 

as northern flicker (Moore 1995), pinyon jay (Balda et al. 

1977), chipping sparrow (Mannan and Meslow 1984), 

dark-eyed junco (Deborah M. Finch and Rebecca Kimball 

pers. obs.), and green-tailed and spotted towhees 

(Deborah M. Finch and Rebecca Kimball pers. obs.) may 

be favored by removal of patches of dense understory 

vegetation through grazing. Even when grass cover remains, shorter grasses may be preferred foraging habitat 

for some species, such as American robin (Eiserer 1980) 

and mountain bluebird (Power and Lambert 1996). However, ground feeders that forage among leaf litter, for example, towhees, may be negatively affected if high levels 

of grazing reduce all or most of the litter. 

Changes in Tree Density 

the trees are small and young. Therefore, bird species that 

prefer dense, old-growth forests may decrease in abundance 

in grazed forests dominated by young trees even though tree 

densities are high. 

Grazing may also lead to increases in the density of tree 

species other than ponderosa pine. In southern Utah, comparison of a grazed and ungrazed area indicated that grazing had greatly increased the number of oak and juniper 

trees in ponderosa pine forests (Madany and West 1983). 

Grazing also increased juniper densities in a ponderosa 

forest in California (Laudenslayer et al. 1989). Oak 

(Quercus spp.), juniper (Juniperus spp.), and pinyon pine 

(Pinus edulis) provide important food resources, particularly for birds that are winter residents and whose winter 

diets depend heavily on access to their nuts and berries, 

such as Lewis' woodpecker, acorn woodpecker, Clark's 

nutcracker, and Townsend's solitaire. Increases in these 

tree species should positively affect the ability of those 

bird species, as wellas other bird species that consume 

nuts and berries, to overwinter successfully in ponderosa -. Grazing generally leads to an increase in the density of pine forests. 

ponderosa pines in the Southwest (Cooper 1960; Madden 

and West 1983) and in other Western forests (Laudenslayer 

et al. 1989; Rummell 1951; Zimmerman and Neuen- Effects in Riparian Zones 

schwander 1984). The reduction in grass and other understory vegetation reduces competition for pine seedlings, and hence greater establishment of seedlings occurs 

in areas that have been grazed (Covington and Moore 

1994a,b; Doescher et al. 1987; Karl and Doescher 1993). In 

addition, several grass species (Arizona fescue, mountain 

muhly, and squirreltail) produce allelopathic compounds 

that inhibit germination of ponderosa pine seeds (Jameson 

1968; Rietveld 1975). If these grass species are reduced 

through grazing, germination of pine seedlings may increase, leading to further increases in pine densities. 

Through this same process, pine trees may also encroach 

into meadows and clearings within the forest. 

Many bird species of ponderosa pine prefer more open 

woods (table 6). As tree densities increase in relation to 

fire exclusion and overgrazing, populations of these bird 

species may begin to decrease. Supporting this hypothesis, Verner (1980) observed the greatest number of bird 

species in areas of lower canopy cover in coniferous forests of the Sierra Nevadas of California. In addition, several bird species associated with ponderosa pine forests 

primarily live in these meadows or clearings (table 6), and 

these species could be excluded from the area as clearings become forested. 

While increases in tree density may lead to decreases in 

many avian species, it is less clear whether any species 

will increase in abundance. Several species are thought to 

prefer dense, old-growth forests including hairy woodpecker (Hejl1994). However, old-growth forest is characterized by large trees, which may be more important than 

tree density. When tree densities increase due to grazing, 

Cattle forage disproportionately in and around riparian zones in forested habitats (Roath and Krueger 1982a, 

b; Samson 1980; Willard 1990) including Southwestern 

ponderosa pine forests (Glendening 1944). Clary et al. 

(1978) suggested that cattle preference for riparian zones 

in ponderosa pine forests may be minimized by careful 

range management practices that increase forage in surrounding areas by thinning trees to promote understory 

growth. 

Vegetation in riparian zones of Rocky Mountain forests 

often differs from that in the surrounding area (Peet 1988) 

and may provide unique habitats for some nesting birds. 

Grazing, particularly since cattle selectively forage in riparian zones, can change the composition and structure 

of the unique riparian community. Observations in a variety of habitats have shown that herbaceous and woody 

vegetation may be trampled or removed, changed in plant 

form or habitat structure, or transformed to different seral stages or vegetation types in response to grazing (Bock 

et al. 1993; Fleischner 1994; Krueper 1996; Rinne 1985; 

Szaro 1989). Heavy grazing in combination with drought 

or dewatering of streams due to irrigation or flood control can reduce regeneration of deciduous native trees, 

altering plant species composition and age structure, and 

encouraging invasion of aggressive alien plants (Finch et 

al. 1995). These alterations in the vegetation may greatly 

affect bird communities in riparian areas. 

Riparian zones of the Western United States have been 

identified as important habitats for breeding birds since 

more species and individuals are often found in the riparian zone than in the surrounding vegetation (reviews in 

120 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Effects and Interactions of Fire, Logging, and Grazing 

Table 6. Bird species in ponderosa pine forests that prefer 

an open habitat or that use meadows or clearings within 

the forest. 

Species Reference 

Open forest species 

Rufous hummingbird 

Northern flicker 

Olive-sided flycatcher 

Western wood-pewee 

Dusky flycatcher 

Gray flycatcher 

Buff-breasted flycatcher 

Ash-throated flycatcher 

Cassin's kingbird 

Violet-green swallow 

Pinyon jay 

Black-capped chickadee 

White-breasted nuthatch 

House wren 

Ruby-crowned kinglet 

Western bluebird 

Townsend's solitaire 

Solitary vireo 

Warbling vireo 

Yellow-rumped warbler 

Calder 1993 

Moore 1995 

Hejl 1994 

DeGraaf and Rappole 1995 

Sedgwick 1993 

Cannings 1987; DeGraaf and 

Rappole 1995 

Bowers and Dunning 1994 

DeGraaf and Rappole 1995 

DeGraaf and Rappole 1995 

Brown et al. 1992 

Balda and Bateman 1972; 

Marzluff (this volume) 

Smith 1993 

Pravosudov and Grubb 1993 

Belles-Isles and Picman 

1986 

Mannan and Meslow 1984 

DeGraaf and Rappole 1995 

DeGraaf and Rappole 1995 

DeGraaf and Rappole 1995 

DeGraaf and Rappole 1995 

DeGraaf and Rappole 1995 

 lack-throated gray warbler DeGraaf and ~appole 1995 

Hepatic tanager 

Western tanager 

Black-headed grosbeak 

Chipping sparrow 

Meadow and clearing species 

Tree swallow 

Mountain bluebird 

Yellow warbler 

MacGillivray's warbler 

Common yellowthroat 

Indigo bunting 

Spotted towhee 

Green-tailed towhee 

Lincoln's sparrow 

American goldfinch 

Lesser goldfinch 

DeGraaf and Rappole 1995 

DeGraaf and Rappole 1995 

DeGraaf and Rappole 1995 

Mannan and Meslow 1984 

Robertson et al. 1992 

Power and Lombardo 1996 

DeGraaf and Rappole 1995 

Pitocchelli 1995 

DeGraaf and Rappole 1995 

DeGraaf and Rappole 1995 

DeGraaf and Rappole 1995 

DeGraaf and Rappole 1995 

DeGraaf and Rappole 1995 

Middleton 1993 

Deborah M. Finch 

(personal observation) 

Bock et al. 1993; Fleischner 1994; Krueper 1993,1996; Saab 

et al. 1995). However, this may not be true in all ponderosa pine forests. A study in Colorado found few unique 

breeding species in a ponderosa pine riparian zone, 

though riparian zones in other habitats were characterized by unique breeding species (Knopf 1985). In addition, in 1 of 2 years of the study, the density of breeding 

birds was not different between the riparian zone and the 

Table 7. Bird species that use riparian tones adjacent to 

ponderosa pine for nesting and foraging. 

Species 

Broad-tailed hummingbird 

Rufous hummingbird 

Acorn woodpecker 

Northern flicker 

Olive-sided flycatcher 

Cordilleran flycatacher 

Buff-breasted flycatcher 

Ash-throated flycatcher 

Cassin's kingbird 

Gray-breasted jay 

Black-capped chickadee 

Canyon wren 

Orange-crowned warbler 

Virginia's warbler 

Yellow warbler 

MacGillivray's warbler 

Red-faced warbler 

Common yellowthroat 

Black-headed grosbeak 

Spotted towhee 

Lincoln's sparrow 

Reference 

Calder and Calder 1992 

DeGraaf and Rappole 1995 

Koenig et al. 1995 

Moore 1995 

DeGraaf and Rappole 1995 

DeGraaf and Rappole 1995 

Bowers and Dunning 1994 

DeGraaf and Rappole 1995 

Blancher and Robertson 1984 

Brown 1994 

Smith 1993 

Jones and Dieni 1995 

Sogge et al. 1994 

DeGraaf and Rappole 1995 

DeGraaf and Rappole 1995 

Pitocchelli 1995 

Martin and Barber 1995 

DeGraaf and Rappole 1995 

Hill 1995 

DeGraaf and Rappole 1995 

DeGraaf and Rappole 1995 

surrounding vegetation. Therefore, riparian zones in some 

ponderosa pine forests and in some years may be less 

important for bird communities than are riparian zones 

in most other habitats. 

Cattle grazing in riparian zones has negatively affected 

bird communities in a variety of Western habitats (Bock 

et al. 1993; Fleischner 1994; Krueper 1993,1996; Saab et al. 

1995). Although there may be few or no species that breed 

exclusively in riparian zones of ponderosa pine forests 

(Knopf 1985), many species do use riparian habitats (table 

7) and may be affected by grazing or trampling of riparian vegetation. Studies of a montane river in New Mexico 

showed that grazed areas had fewer bird species and fewer 

individuals, as compared with an ungrazed portion of the 

same river (Szaro and Rinne 1988). However, studies of 

montane riparian zones in Idaho and Nevada found no 

decrease in species numbers in a grazed as compared to 

an ungrazed area (Medin and Clary 1990,1991). In addition, northern flicker and American robin increased in 

abundance in a grazed riparian habitat (Mosconi and 

Hutto 1982; Schulz and Leininger 1991), probably due to 

an increase in open ground on which to forage (Knopf 

1996). Therefore, grazing does not always reduce bird 

abundance and species richness in riparian habitats. Indeed, population responses to changes in riparian habitat 

resulting from grazing appear to be species dependent 

(Saab et al. 1995). Populations of individual bird species 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 6 

may increase, decrease, or remain constant in relation to 

grazing, contributing to changes in avian community 

structure. Since riparian zones in ponderosa pine forests 

are likely to vary in structure and vegetative composition, 

grazing may negatively affect some bird populations in 

some areas but probably not all species in all areas. High 

grazing intensity (high stocking rate), continuous yearround grazing, and grazing during the critical breeding 

season are perhaps the most significant management practices that alter avian habitats in riparian zones. 

Cattle can also affect other aspects of the stream, which 

may indirectly affect birds in the area. Studies in Southwestern forests have shown that cattle can damage stream 

banks (Rinne 1985), which leads to stream widening. Grazing also reduces vegetation around and overhanging 

streams in the Southwest and elsewhere (Platte and Raleigh 1984; Rinne 1985), leading to an increase in stream 

temperature and a reduction in the amount of detritus in 

the stream. Silt loads in the streams may also increase, 

reducing the size or presence of interstitial spaces that are 

used by aquatic invertebrates (Rinne 1985). While these 

changes might negatively affect aquatic insects, an important food for birds, comparison of a grazed and ungrazed 

region of a montane stream in New Mexico found that 

the grazed region had increased numbers and biomass of 

aquatic insects (Rinne 1988). Thus, grazing may make 

some streams more hospitable for aquatic insect larvae 

that emerge as flying insects and become food for birds. 

Assuming that many bird species in ponderosa pine forests are insect generalists (Brawn et al. 1987), increases in 

insect abundances, even if the species composition of the 

insects has changed, may benefit some bird species. 

Other Effects of Livestock Management on 

Birds 

Added Water Sources 

While cattle grazing may affect ponderosa pine bird 

communities by altering the habitat, birds may also be 

affected by other range management practices. Areas 

where cattle are grazed are often supplied with stock tanks 

or other artificially created water supplies. These water 

sources can benefit bird communities because they provide water for drinking and bathing and emergent insects 

to feed upon. However, additional water sources may have 

some negative affects on bird communities. Livestock traffic may greatly reduce the vegetation around the water 

source, possibly damaging nesting and foraging sites (Buttery and Shields 1975). In addition, the water source may 

attract predatory mammals and snakes, which may increase avian nest predation in the area (Buttery and Shields 

1975). Other bird species or individuals may colonize the 

site, increasing site activity and competing for local resources. Stagnant water also provides prime breeding 

habitat for mosquitoes. While mosquitoes provide food for 

many avian species, they also carry malaria (Plasmodium 

spp.), which can infect avian populations. Avian malaria is 

common in most bird communities and can be detrimental 

to an individual's health or survival, particularly for birds 

that may be under stress (Hayworth and Weathers 1987). 

Brown-Headed Cowbirds 

In addition to grazing in forested areas, cattle may be 

moved to feedlots outside forest boundaries. Although, 

few forest birds are likely to travel far from forests to forage at open feedlots, brown-headed cowbirds in many 

regions of the United States are attracted to areas with 

supplemental food such as feedlots and pack stations 

(Lowther 1993; Rothstein et al. 1980; Thompson 1994; Trail 

and Baptista 1993; Verner and Ritter 1983). Radio-telemetry studies in the Sierra Nevada Mountains and the Midwest have shown that cowbirds will travel long distances 

(up to 10 km) between feeding and nesting areas 

(Rothstein et al. 1984; Thompson 1994). Therefore, even when 

feedlots are placed outside forested areas, they may increase 

the presence of cowbirds in local ponderosa pine forests. 

The range expansion of the brown-headed cowbird into 

the Western United States has been well documented 

(Rothstein 1994). In addition to foraging for insects in feedlots, dairy farms, pastures, and other artificial habitats, 

cowbirds also follow cattle to scavenge insects and seeds 

from dung (Terborgh 1992). Therefore, the expansion of 

cowbirds into new habitats and geographic areas may be 

facilitated by the presence of agriculture and cattle (Hanka 

1985; Rothstein 1994; Sharp 1995). Cowbird populations 

in New Mexico, but not Arizona, are increasing (Mehlman 

1995) and further studies may help clarify whether cowbird densities are related to numbers of feedlots and cattle. 

Some habitat changes associated with grazing may actually decrease the presence of brown-headed cowbirds 

in ponderosa pine forests. Cowbirds typically prefer open 

habitats, and they travel into forested areas primarily to 

lay eggs in host nests (Verner and Ritter 1983). Verner and 

Ritter (1983) suggest that differences in the cowbird distribution in the Sierra Nevada Mountains may be due to 

differences in forest density, with cowbirds avoiding dense 

coniferous forests. If this is true for Southwestern ponderosa pine forests, increases in tree density due to grazing 

and fire exclusion may make these forests less hospitable 

to cowbird invasions. 

Since brown-headed cowbirds lay their eggs in the nests 

of other species, the reproductive output for parasitized 

individuals is greatly reduced because the nest is either 

abandoned or the host young do not survive to fledgling 

(Robinson et al. 1995a). Female cowbirds can lay up to 30 

or 40 eggs a year (Scott and Ankney 1980); 1 female can 

affect the reproductive success of many different breeding pairs. However, while they affect host species, they 

may not be the primary cause of population declines of 

most host species. Instead, cowbirds may cause additional 

122 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Effects and lnteractions of Fire, Logging, and Grazing 

stress to populations already stressed from other factors 

such as habitat loss (Rothstein 1994). 

Brown-headed cowbirds occur at least occasionally in 

ponderosa pine forests of the Southwest especially along 

edges, riparian zones, campgrounds, and clearings. Cowbirds are generalist brood parasites, and many songbird 

species in ponderosa pine forests have been observed to 

raise cowbird young (Friedmann and Kiff 1985; Martin 

and Barber 1995), although other species reject cowbird 

eggs by ejecting them from the nest. Most ponderosa pine 

birds suffer only low levels of parasitism, but vireos, warblers, sparrows, gnatcatchers, tanagers, and towhees are 

commonly parasitized in at least some habitats (riparian 

zones) (Friedmann and Kiff 1985; Goguen 1994; Schweitzer 

and Leslie 1996). It is unknown whether levels of parasitism would increase for all species if cowbirds became more 

abundant or whether the few commonly parasitized species would be the primary targets, with other species remaining occasional hosts. 

Little information is available on cowbird populations, 

parasitism rates, host selection, and host nesting success 

for Southwestern ponderosa pine forests. In pinyon-juniper woodlands near Raton, north central New Mexico, 

Goguen (1994) reported cowbird parasitism rates of 80 to 

100 percent for solitary vireo; 78 to 92 percent for western 

tanager; 63 to 75 percent for blue-gray gnatcatcher; 0 to 

13 percent for chipping sparrow; 0 to 25 percent for spotted towhee; and 0 to 14 percent for western wood-pewee. 

According to Goguen (1994), cowbird parasitism rates 

were usually greater in areas where cattle were present. 

In addition, the nesting success of parasitized nests varied greatly by host species (Goguen 1994). These same host 

species also occupy Southwestern ponderosa pine forests 

and may be parasitized in these forests. 

Southwestern studies focusing on cowbird abundances 

and affects on hosts are limited to riparian zones at elevations lower than the ponderosa pine zone. According to 

Schweitzer and Leslie (1996), cowbird densities and parasitism rates vary greatly by locality. We suggest that cowbird parasitism may pose a problem for some ponderosa 

pine hosts in areas where forests are within 4 to 6 miles of 

open pastures, stockyards, corrals, stock tanks, and agricultural fields (Rothstein et al. 1984,1987). More research 

is needed to determine whether and where cowbird densities and parasitism rates are high or low in ponderosa 

pine compared to other habitats, and whether rates of 

parasitism are associated with characteristics such as proximity to and extent of edge, habitat fragmentation and 

isolation, density of ponderosa pines, forest successional 

stage, dispersed or concentrated grazing, host species 

presence or absence, and host densities. 

Vulnerable species may include small, open-nest, 

neotropical migrants that produce only 1 brood a year (flycatchers, vireos, warblers) (Mayfield 1977), and hosts occupying isolated, patchy habitats (Rothstein et al. 1987; 

Rothstein and Robinson 1994). Small, disjunct host populations are more at risk of extirpation from cowbird 

parastism than abundant hosts because cowbirds do not 

reduce parasitism rates as preferred hosts become rare 

(Mayfield 1978; May and Robinson 1985). Birds nesting 

in Southwestern riparian habitats are considered especially vulnerable to cowbird parasitism because this habitat is typically patchy, linear, and ecotonal; often near or 

within cattle pastures or agricultural fields; and preferred 

as bongregation grounds by cows (Harris 1991; Schweitzer 

and Leslie 1996; Schweitzer et al. 1996). 

Subdivision of Private Ranches 

Increases in grazing fees may lead ranchers to subdivide their land. While subdivisions replace wildlife habitat, developments are generally concentrated and use a 

relatively small proportion of the land (Wuerthner 1994). 

As such, subdivision may benefit avian communities, as 

grazing would cease while much land would still remain 

undeveloped. However, development requires water and 

this will damage or destroy riparian habitats (Brown and 

McDonald 1995), which will negatively affect many bird 

species. Subdivision also fragments the habitat, increasing edges and establishing possible barriers to dispersal. 

Additional problems associated with subdividing land 

into developed properties are described by Marzluff (this 

volume). Fragmentation and the associated increase in 

edges increases nest predation and nest parasitism by cowbirds (Gates and Giffen 1991; Paton 1994; Robinson et al. 

1995b), although not all studies have found that edge nests 

were more heavily parasitized than were interior nests 

(Hahn and Hatfield 1995). Subdivisions also reduce patch 

size of suitable habitat. Large patches of forest habitat are 

preferred by species, such as the hermit thrush (Keller and 

Anderson 1992), and these may decrease in abundance if 

fragmentation occurs. While these species may decrease, 

other species, such as the pine siskin and the Cassin's finch, 

may increase in abundance (Keller and Anderson 1992). 

Both grazing and subdivision of ranch land will, on average, negatively affect some bird species. Given existing 

data, it is difficult to determine which factor, grazing or 

subdivision, will have the lowest negative impact on avian 

communities. 

lnteractions of Fire, Grazing, and 

Logging 

Fire, Salvage Logging, and Forest Health 

Salvage logging primarily occurs in response to 3 causes 

of tree mortality: 1) insect attack; 2) tree diseases; and 3) 

fire. Salvage operations can help control insect pests and 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 6 

pathogens by removing dead, dying, or high risk trees, 

and by helping to make a stand less susceptible to future 

catastrophic fire and insect outbreaks. Wood fiber that 

would deteriorate is salvaged. However, salvage logging 

in response to forest disease treats only the effect and not 

the cause of the problem. Following intense fire, salvage 

logging is implemented to help recover the economic 

value of fire-killed trees. Whether or not dead and dying 

trees should be removed from a site is possibly the most 

controversial aspect of forest health management today 

(OfLaughlin et al. 1993; Filip et al. 1996). 

Regardless of the reason for a salvage operation, the 

result is the removal of dead and dying trees from a forest 

stand. Bird species that depend on dead and dying trees 

(snags) are most impacted by any type of salvage logging, 

whether it be selective harvest of individual trees or complete stand removal. Cavity nesters in ponderosa pine 

forests of the Southwest, such as the acorn woodpecker, 

hairy woodpecker, northern flicker, pygmy nuthatch, 

white-breasted nuthatch, western bluebird, mountain 

chickadee, house wren, Cordilleran flycatcher, and violet-green swallow (Szaro and Balda 1979a), will potentially 

be affected the most. Snags also provide important habitat features for other species (Glinski et al. 1983; Hutto 

1995; Sallabanks 1995). 

Empirical data on the response of ponderosa pine bird 

communities to salvage logging is limited and currently 

restricted to fire-related snag removal (Overturf 1979; 

Moeur and Guthrie 1984). Other studies offer insights into 

the response of general forest bird communities to snag 

harvest following fire, which can be cautiously extrapolated to ponderosa pine bird communities. 

Raphael and White (1984) found 77 percent fewer pairs 

of cavity-nesting birds 5 years after complete snag removal 

on a burned plot in the Sierra Nevada Mountains. This 

decline was largely due to the disappearance of mountain bluebirds. Pairs of noncavity-nesters declined by only 

6 percent during the 5 years after harvest. Of 3 cavitynesting species reported before snag removal, only the 

northern flicker still bred on the plot post-harvest. 

Raphael (1983) explored the bird response to reduced 

snag densities by simulating various snag-harvest levels 

immediately following fire. The 19 snag-harvest treatments simulated varied from leaving 1 to 10 percent of 

the pretreatment snag density (in 1 percent increments) 

to leaving 20 to 100 percent (in 10 percent increments). 

Total bird numbers rose dramatically from the 1 to 10 percent treatment level (corresponding to 0 to 4.5 snags >38cm 

dbh per hectare). Beyond the 30 percent treatment level 

(15 snags/ha), bird response rose relatively slowly. The 

model predicted that optimum snag densities under the 

constraints tested would be 7 to 15 snags/ha. 

Hutto (1995) reported on ongoing studies of bird communities in burned forests in the northern Rocky Mountains. These studies suggested that some bird species require burned forests to maintain viable populations. Further, bird species differed in the microhabitats that they 

occupy within a burn. Therefore, salvage prescriptions that 

tend to homogenize forest structure (selective removal of 

all trees of a certain size) are unlikely to maintain the necessary variety of microhabitats within a burned forest. 

Consequently, Hutto (1995) suggested that where salvage 

logging is necessary, it may be better to take trees from 

one part of a bum and leave another part completely untouched rather than selectively remove trees from the entire burn area. Noting that up to 60 percent of all timber 

sales on some forests in the northern Rocky Mountains involve salvaged timber, Hutto (1995) also argued that postfire salvage cutting may be conducted more frequently than 

justified on the basis of sound ecosystem management. 

In addition to these studies, 3 studies in progress will 

offer much-needed data on the effects of salvage logging 

on songbird communities. Because these are not occurring in ponderosa pine forests of the Southwest, their relevance is unknown. The first is a study of subalpine fir 

(Abies lasiocarpa) forests in the Blue Mountains of northeastern Oregon where fire-killed trees will be salvage 

logged (Sallabanks 1995). The second study examines how 

fire and salvage logging in ponderosa pine forests of west 

central Idaho influence the nest success of 10 cavity-nesting bird species (V. A. Saab pers. comm.). Salvage logging 

is underway in the third study in lodgepole pine (Pinus 

contorta) forests in south central Oregon (Arnett et al. 1996). 

This study is important because it will examine salvage 

of trees killed by the mountain pine beetle (Dendroctonus 

ponderosae) rather than wildfire. All 3 studies have collected 

presalvage data on breeding bird community composition 

so that pre- and post-salvage data may be compared. 

Although little empirical data exists on the effects of 

snag harvest on wildlife populations following fire, even 

less is known about the effects of salvaging diseased and 

insect-infested trees on bird communities. Because bird 

communities differ between burned and unburned sites, 

the effects of salvage operations on birds may also differ 

between these sites. Therefore, extrapolating results from 

studies of salvage logging in burned sites to unburned 

sites may be unjustified. This area needs further research. 

Relationships between bird communities and general 

forest health are also poorly defined for ponderosa pine 

forests. When forests are overstocked due to a recent history of fire suppression, trees are susceptible to a variety 

of insects and diseases and severe wildfires, especially 

during drought conditions. In some Western states, ponderosa pine forests are dying faster than they are growing (O'Laughlin et al. 1993). Insectivorous bird species 

would presumably benefit from insect outbreaks such as 

those by the Douglas-fir tussock moth. Similarly, cavitynesters should benefit in the short term from tree mortality that occurs as a result of insect attack, disease, or wildfire. In the long term, however, processes that result in 

124 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Effects and Interactions of Fire, Logging, and Grazing 

tree mortality exceeding tree recruitment are problems for 

forest birds. 

Bird regulation of insects that cause tree mortality is 

pertinent to forest health conditions. Birds consume large 

numbers of defoliating insects (Crawford et al. 1983). Without bird predation, it is estimated that spruce budworm 

populations would reach epidemic densities every 3 years 

in the Pacific Northwest (Takekawa and Garton 1984); 

actual epidemics occur about every 28 years (Dolph 1980). 

When insects are at endemic levels, avian predation is 

most effective. Crawford et al. (1983) report that in northern New England, the percentage of spruce budworm larvae and pupae eaten by birds declined from 87 percent to 

2 percent of the budworm population at endemic and 

epidemic levels, respectively. 

The relationship between forest health, salvage logging, 

and bird communities in Southwestern ponderosa pine 

forests is complex and poorly understood. The apparent 

decline in some species of forest-breeding neotropical 

migrant songbirds (Finch 1991) may profoundly affect 

forest health if the insects normally eaten by these bird 

species are frequently allowed to reach epidemic levels. 

Increases in insect attack may lead to weaker trees that are 

more susceptible to disease. This, combined with drought 

and management to suppress fires, could increase fuel loads 

and the chance of large, catastrophic, stand-replacing wildfires. Such fires could lead to more salvage logging and further changes in the ponderosa pine bird communities. Given 

the complex nature of these interactions among components 

of the ponderosa pine ecosystem, more research is needed 

on the effects of salvage logging on bird communities, the 

role of songbirds in maintaining forest health, and the relationship between insects, disease, fire, and birds. 

Cumulative Effects of Fire, Grazing, and 

Logging 

Pre-European forests of the Southwest tended toward 

a wider range and diversity of tree sizes and ages, health 

states, patch ages, structural stages, inter- and intra-patch 

diversity, and landscape designs than do contemporary 

ponderosa pine forests. Historically, bird species with specialized needs were found at varying abundances at different, but overlapping, intervals along this temporal and 

spatial continuum of forest age, health, and diversity. 

Based on the analyses and studies described above, bird 

species that historically preferred open, park-like ponderosa pine forests are likely to be negatively affected by 

contemporary forest management that emphasizes continuous or long-term grazing in combination with fire 

exclusion because these practices produce a closed forest 

of dense, young to mid-aged trees with few grasses, forbs, 

or shrubs. Such vegetation changes result in poor grazing 

conditions for cattle, too. In addition, modem-day culling 

and salvage logging of snags, diseased trees, and old trees, 

and clearing of old growth patches reduces the diversity and 

heterogeneity of stand ages and structures, intensifymg the 

trend toward younger, more uniform, even-aged forests. 

When the influences of fire exclusion, long-term grazing, and old-growth logging (heaviest in the first half of 

the 20th century) are fused into one management package, the resulting forests of the Southwest tend to be more 

mid-aged than young or old, more dense than open, and 

more plantation-like than variable in tree size, spacing, 

aAd understory structure. Midsuccessional stages dominate contemporary Southwestern ponderosa pine forests 

and are probably used to the greatest extent by bird species generalists adapted to a broad range of forest and 

structural types (American robin, dark-eyed junco). They 

may be avoided by bird species that require special habitat elements only found in open forests, old growth, burns, 

snags, heterogeneous landscapes, or a combination of 

these conditions. However, Brawn and Balda (1988a) reported that no bird species of Southwestern ponderosa 

pine forests has gone extinct since early turn-of-the century surveys (Scurlock and Finch this volume), which 

suggests that habitat changes caused by forest management have not been so extreme as to eliminate any species, at least at the broadest spatial scales. 

Species of concern that are likely to be negatively affected by forest management that emphasizes continuous 

grazing, fire exclusion, and post-fire salvage logging include those that nest in or forage on or from standing dead 

trees or large, old trees in open forests; for example, the 

three-toed woodpecker, pygmy nuthatch, white-breasted 

nuthatch, and mountain and western bluebirds. Additional open-forest species that may benefit from prescribed 

fire or thinning of young trees include Grace's warbler, 

rock wren, western wood-pewee, and chipping sparrow. 

Shrub-using species of open or heterogeneous forests that 

may benefit from livestock pasture rotation in combination with burning or clearing to increase amounts of early 

successional shrubs are broad-tailed hummingbird, dusky 

flycatcher, MacGillivrayls warbler, orange-crowned warbler, Virginia's warbler, Bewick's wren, solitary vireo, 

white-crowned sparrow, Lincoln's sparrow, and spotted 

towhee. 

Species whose abundances in Southwestern ponderosa 

pine are known or suspected to decline in relation to burns, 

clearcuts, natural clearings, or partial-logging, for example, the pygmy nuthatch, mountain chickadee, redfaced warbler, hermit thrush, violet-green swallow, Cordilleran flycatcher, pine grosbeak, and black-headed 

grosbeak, may respond negatively to local management 

implemented for economic gain or to benefit open-forest 

species. Such immediate reactions are short-lived for species that can occupy subsequent successional stages, but 

are longer-lasting for those that reach peak abundance in 

the oldest forests. While old-growth species may avoid 

open patches created by intense burns or clearcutting, 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 125 
Chapter 6 

fewer of them avoid larger, more diverse landscapes, which 

can include small and large patches of dense old trees, open 

young forest, and open old-growth forest. For example, the 

pygmy nuthatch, a species that uses snags created by fires, 

old age, and disease to nest and roost in, avoids local bums 

that may increase snag density. The solution to maintaining 

populations of all songbird species in Southwestem ponderosa pine may be to ensure that suitable habitat resources 

are available at the landscape and physiographic levels, while 

acknowledging that local resources may not always be sufficient to satisfy the needs of all species. 

Research Needs 

The effects of fire, logging, and grazing on bird communities in ponderosa pine forest need further study. We 

describe some specific areas where further research is 

needed for each management practice. Probably the most 

critical research need is to understand the interactive effects of fire, logging, and grazing. For example, what bird 

species can be expected in ponderosa pine forests when 

managing along a gradient ranging from wilderness and 

research natural areas to areas combining fire exclusion, 

prescribed fire, continuous and rotational grazing, evenaged and uneven-aged silviculture, and salvage logging? 

Evaluating interactive effects will require complex study 

designs, high amounts of funding, close working relationships between management and research organizations, 

and a large team of scientists, land managers, and technical support staff. Research goals can most realistically be 

met if fewer interactions and objectives are addressed in 

each individual study. Research needs specific to each 

management practice are discussed below. 

Research in Relation to Fire 

Bird communities should be monitored through time 

on areas burned by large, intense wildfires to evaluate the 

effects of such fires on bird communities and how these 

communities change through time following fire. This will 

require opportunistic rather than planned studies. Studies should focus on fires that differ in size and intensity, 

so that changes in bird communities can be documented 

over a wide range of fire behavior. Long-term studies are 

needed to document changes in bird communities through 

various phases of post-fire succession. Studies should focus on response patterns of individual species and should 

Bird communities should be studied experimentally in 

conjunction with prescribed burning. Studies should consider the above factors and the effects of a wide range of 

fire prescriptions on important habitat components. Because current forest conditions may result in an unacceptably high loss of some important habitat components even 

with applications of cool fire, it may be necessary to take 

special steps to protect these components in the short term. 

Therefore, techniques to mitigate the negative effects of 

fire on'important habitat components, such as snags, 

should be tested and evaluated. As more natural fire regimes are restored, this problem should be alleviated and 

special protective measures may no longer be required. 

The effects of salvage logging on post-fire bird communities and on recovery of forest structure should be studied experimentally, keeping in mind the factors listed 

above. Studies should include a wide range of logging 

prescriptions, as different prescriptions have different affects on birds and their habitat. 

Efforts should be made to identify any species that are 

dependent on or sensitive to fire, and to evaluate the positive and negative effects of fire on those species. The threetoed woodpecker may be the species most closely linked 

to fire in the Southwest. This woodpecker is generally rare, 

but is capable of colonizing burned areas rapidly and in 

relatively high numbers (Koplin 1969; Wauer and Johnson 

1984), suggesting that recruitment may occur over large 

distances (Wauer and Johnson 1984). Other species may 

also be partially dependent on fire to create and maintain 

suitable habitat. 

To the extent possible, the range of variation in patch sizes 

of natural (pre-European settlement) bums should be evaluated so that managers can attempt to mimic natural disturbance patterns through prescribed burning (DesGranges and 

Rondeau 1993). In addition, the natural (pre-European settlement) range of fuel loadings should be determined so that 

fire managers can bring current conditions in line with historical conditions. Studies comparing the effects of fire to 

those of timber harvest are also needed. Studies should evaluate whether or not timber harvest can simulate the effect of 

fire on forest birds and, if so, under what prescriptions. 

Studies exploring the relationship between grazing, fire 

suppression, forest structure, and bird communities are 

also required. Many areas now contain dense forest stands 

as a result of heavy grazing pressure in the past, coupled 

with fire suppression (Rummel 1951; Madany and West 

1983). Restoring fire to these areas may require special 

considerations such as those described in the second paragraph of this section. 

evaluate demographic patterns and patterns of resource 

use. Studies should consider breeding and nonbreeding Research Pertaining to Silviculture 

birds and year-round residents and migratory birds, as Conclusions based on our literature review are hamall of these groups are important parts of the overall bird pered by the rarity of studies addressing bird responses 

community. to different kinds of logging and by inconsistencies in re126 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Effects and Interactions of Fire, Logging, and Grazing 

search designs. Most reports have considered only the 

effects of timber harvesting and were limited to relatively 

small spatial and temporal scales. In addition, most of 

these studies used secondary variables such as presence, 

absence, or relative abundance of species rather than demographic attributes such as reproductive output, mortality, and recruitment and return rates to indicate population trends and habitat suitability (Martin 1992). More 

importantly, past studies have lacked pretreatment monitoring, controls, and/or replicates, and relied on correlative 

evidence instead of direct experimental manipulations to 

assess avian habitat relationships. Present ponderosa pine 

forests, although relatively simple in species composition, 

are nevertheless a complex spatial mosaic that vary in age, 

health (related to disease and insects), germination history, fire history, elevation, slope exposure, microclimate, soil 

conditions, composition of flora and fauna, livestock management, and silviculture (Brawn and Balda 1988). Although 

most researchers attempt to standardize study plots by selecting "similar" stands and site characteristics for different 

treatments, stand vegetation may be perceived differently 

by avian species. In addition, logging treatments vary in size, 

selection criteria, treatment type, and time of treatment. 

We recommend that long-term research and monitoring 

of bird populations, bird demographics, habitat use, and 

habitat structure be implemented in relation to different types 

of silviculture, successional stages, and landscape patterns. 

Studies should be designed to address local and landscape 

levels simultaneously to determine if patterns in bird habitat use shift with scale of resolution. Whereas changes in 

densities and diversities of birds may be relatively small 

within each treatment plot, they may be significant when 

summed across a landscape. Improved techniques and increased applications for inventorying, mapping, and monitoring stages and types of ponderosa pine at large geographic 

and temporal scales are needed to understand where and 

how ponderosa pine forests and associated avifaunas have 

changed at any given time and to enable adjustments in forest management when undesirable trends are identified. 

Further research on songbirds is needed to determine 

population size and age structure, rate and direction of 

population changes, age-specific fecundity and survival, 

adult and juvenile dispersal, breeding success, mortality, 

predation rates, and return rates in relation to timber harvesting, stand age and regeneration time, intermediate 

treatments, and logging rotation schedules, and size, heterogeneity, and isolation of managed forests. Whitcomb 

et al. (1981) reported that species sensitive to fragmentation in Eastern deciduous forests were neotropical migrants that inhabited forest interiors, nested on or near 

the ground in open nests, and had relatively low reproductive potential. Such information is critical for understanding why, where, and which bird species are positively 

or negatively affected by logging directly and/or by associated sera1 fragmentation of forested landscapes. 

Whether similar or different population and demographic 

associations exist among avian species using ponderosa 

pine forests in the Southwest has yet to be discovered; 

however, based on exploratory studies of bird habitat relationships, more resident bird species in Western coniferous forests seem to respond negatively to reductions in 

densities and amounts of mature and old growth forests 

than do nontropical migrants (Hejl et al. 1995). 

Many avian species that use Southwestern ponderosa pine 

forksts are transients or wintering residents. While past research has mostly focused on breeding birds, responses of 

nonbreeding populations to habitat alterations should be 

studied. During migration and winter, most bird species use 

a wider range of habitats, indicating greater habitat plasticity (James 1971; Anderson and Shugart 1974; Moore et al. 

1995). Research is needed to investigate the degree or scale 

at which different bird species discriminate among habitats 

of different ages, structures, spatial patterns, and treatments. 

Given that over one-third of ponderosa pine forests in the 

United States are privately owned (Raish et al. this volume), 

research partnerships between public agencies and private 

entities are strongly recommended. 

Research in Relation to Grazing 

Grazing in ponderosa pine forests is likely to affect the 

abundance and species composition of bird communities 

breeding and living in Southwestern forests. Changes in 

the density and composition of the understory will greatly 

affect birds that nest on or near the ground. 

Understory changes will also affect foraging behavior, 

potentially reducing the foragmg efficiency of foliage gleaners, but increasing the foragmg efficiency of at least some 

ground foragers. Many ponderosa pine bird species prefer 

more open forest habitats and may decrease in response to 

increasing tree density. Grazing also affects riparian zones 

in ponderosa pine forests, although this may not reduce avian 

diversity and abundances. Bird populations may also be affected by other range management practices such as the presence of stock tanks or feedlots. However, these practices are 

likely to have less of an impact on bird communities in ponderosa pine forests than the influence of habitat changes. 

There are several areas of research that need to be addressed before the effects of grazing on ponderosa pine 

bird communities can be understood. Many prior studies 

have suffered from poor experimental design (Brown and 

McDonald 1995), and it is critical to conduct carefully controlled experiments involving replication and either the 

exclusion or addition of cattle. These studies should address such questions as whether breeding and wintering 

bird communities differ between grazed and ungrazed 

forests, whether trampling reduces resting success, 

whether increases in tree density negatively affect many 

species, and whether cowbird populations increase in 

grazed areas. In addition, studies addressing the impact 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 127 
Chapter 6 

of different grazing systems and cattle densities will provide the information necessary to make management decisions that will minimize the impact of grazing on avian 

communities. Although riparian zones are more difficult 

to study due to the many confounding physical factors 

involved (Brussard et al. 1994), it is important to determine whether grazing negatively affects bird communities 

in these areas as well. Finally, other practices associated with 

range management should be investigated to determine if 

and how these might affect songbird populations. 

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USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 7 

Landscape Dynamics and Considerations 

Kevin M. Rich and Patricia Mehlhop 

Introduction 

Landscape ecology is the study of spatial heterogeneity and its influence on organisms and ecological processes 

(Risser et al. 1984). Recent advances in remote sensing 

technologies, computer software and hardware, and methods for quantifymg spatial heterogeneity have contributed 

to the emergence of landscape ecology as a powerful approach for analyzing spatial patterns and their ecological 

consequences. The following references provide a good 

overview of the field of landscape ecology: Forman and 

Godron (1986), Naveh and Leiberman (1994), Pickett and 

Cadenasso (1995), Risser et al. (1984), Turner and Gardner 

(1991), and Urban et al. (1987). 

Table 1 defines key terms in landscape ecology used in 

this chapter. Exact definitions of landscape, patch type, 

and patch depend on the specific organisms and processes 

being studied (Dunning et al. 1992; McGarigal and Marks 

1995; Wiens 1976; Wiens and Milne 1989). Typically, landscapes occupy a spatial scale intermediate between an 

organism's home range and its regional distribution (Dunning et al. 1992). Thus, for songbirds in the Southwest, 

landscapes may be defined ranging in size from a few 

hectares to thousands of square kilometers. The patch type 

Table 1. Definition of several key terms used in landscape ecology. 

of primary interest here is ponderosa pine forest, or forest 

in which ponderosa pine is the sole dominant plant species. Individual patches may range in size from a few trees 

to hundreds of square kilometers, depending on the phenomena and species under investigation, the scale of the 

study and the resolution of any remote sensing imagery used. 

Landscape ecologists generally divide spatial patterns 

observed in landscapes into two categories: landscape 

composition and landscape configuration. Landscape 

composition refers to the variety and abundance of patch 

types within a landscape without considering the location of individual patches (Dunning et al. 1992; McGarigal 

and Marks 1995). An example of a measure of landscape 

composition is the proportion of a given landscape covered by ponderosa pine forest. Landscape configuration 

refers to the spatial relationships between patches in a 

landscape (McGarigal and Marks 1995). For example, one 

might be interested not only in the total amount of ponderosa pine present in a landscape but also in the degree 

to which individual ponderosa pine patches are isolated 

from each other. Both landscape composition and configuration have been shown to have significant influences on 

the distribution and abundance of songbirds (Freemark 

et al. 1995). 

Many studies in Southwestern ponderosa pine forests 

have investigated the relationships between songbirds and 

Term Definition Referencea 

landscape a mosaic of patches relevant to the phenomenon under consideration 

(at any scale) 1 

distinguished by discontinuities in environmental character states from its surround 

implicit is the notion that the discontinuities have biological significance 

a description of the environmental character states differentiating a patch or group of 

similar patches from surrounding areasb 1 

res associated with the presence and amount of each patch type within the landscape 

ut being spatially explicit 1 

distribution or spatial character of patches within the landsc 

lution of the data, that is, the area represented by each data 

e overall size of the study areaC 

t of individuals that all interact with each other with a high probability 

metapopulation set of local populations that interact via individuals moving among populations 4 

a References: 1. McGarigal and Marks (1995); 2. Wiens (1976); 3.Turner et ai. (1989); 4. Hanski and Gilpin (1991). 

Our definition. The term is used, although not explicitly defined, by McGarigal and Marks (1995). 

The terms "grain" and "extent" are also used to refer to the smallest and largest scales at which an organism responds to spatial heterogeneity (Kotliar and Wiens 1990). 

We present the above definitions because we use these terms in describing spatial data sets in the text. 

USDA Forest Service Gen.Tech. Rep. RM-GTR-292. 1997 137 
Chapter 7 

habitat characteristics at the level of individual patches 

(Hall et al. and Finch et al., this volume). To date, though, 

no published studies from Southwestern ponderosa pine 

forests have examined the relationships between songbirds and spatial patterns at the level of entire landscapes. 

In this chapter, we will discuss the importance of scale in 

ecological research, highlight several tools available for 

characterizing landscape patterns in Southwestern ponderosa pine forests, and describe specific research needs 

at fine, intermediate, and large spatial scales. We will also 

address research needs relevant to habitats and species of 

special concern. 

The Importance of Scale 

Different ecological processes occur at different spatial 

scales (Kotliar and Wiens 1990; Urban et al. 1987; Wiens 

1989). Factors affecting habitat selection by individuals 

within patches may differ from factors influencing the 

distribution and abundance of organisms across landscapes (Wiens 1989; Wiens et al. 1987; McGarigal and 

McComb 1995). To fully understand the ecology of songbirds in Southwestern ponderosa pine forests, additional 

research is needed at multiple spatial scales, including finescale studies at the level of individual patches; intermediate-scale studies at the level of landscapes several hundred 

hectares in size; and large-scale studies at the level of landscapes hundreds to thousands of square kilometers in size. 

At different scales, different spatial patterns emerge for 

ponderosa pine forests in the Southwest. At a scale of several hundred hectares, ponderosa pine forests generally 

appear as integral components of larger forests. Ponderosa pine forests often meet and blend with pinyon-juniper along lower elevational boundaries and with Douglasfir and mixed-conifer along upper elevational boundaries. 

At a scale of hundreds to thousands of square kilometers, 

though, Southwestern ponderosa pine forests tend to appear highly fragmented. 

How these spatial patterns influence the songbirds that 

use these forests is unknown. Many studies in forests of 

eastern and central North America have found that 

smaller, more isolated patches tend to have fewer songbird species and fewer individuals of those species than 

larger, less isolated patches (for example, Ambuel and 

Temple 1983; Askins and Philbrick 1987; Blake 1986; Blake 

1991; Blake and Karr 1984; Blake and Karr 1987; Freemark 

and Collins 1992; Freemark and Merriam 1986; Lynch and 

Whigham 1984; Robbins et al. 1989; Whitcomb et al. 1981). 

These studies have generally focused on patches of forest 

surrounded by non-forested agricultural and suburban 

areas. In contrast, several studies in western North 

America have shown little relationship between patch size 

and songbird species richness or abundance in forest 

patches surrounded by forests of different species composition or age and size class (Aney 1984; Lehmkuhl et al. 

1991; Rosenberg and Raphael 1986). Conceivably, songbirds in ponderosa pine forests may show responses characteristic of birds in Eastern fragmented forests at large 

spatial scales, while showing responses characteristic of 

birds in other Western forests at intermediate spatial scales. 

Until landscape-level research on songbirds in Southwestern ponderosa pine forests is carried out, though, such 

comparisons will remain speculative. 

Characterization of Landscape 

Patterns 

A prerequisite for most research in landscape ecology 

is the availability of data on the spatial patterns of interest. All spatial data sets have a certain grain and extent. 

"Grain" refers to the resolution of the data (Turner et al. 

1989). For example, on a relatively fine-grain map, it might 

be possible to distinguish features 1 m in size, while on a 

relatively coarse-grain map these features might not be 

visible. Extent refers to the area covered by the data set. A 

spatial data set is only useful for a given study if it has a 

grain and extent appropriate for the research being carried out (McGarigal and Marks 1995; Turner et al. 1989). 

The data must have a fine enough grain that patch types 

and patches relevant to the organisms and phenomena 

being investigated can be readily distinguished. In addition, the extent must be large enough that meaningful 

spatial patterns can be identified. 

Table 2 provides information on several spatial data sets 

currently available or soon to be available that include 

data on Southwestern ponderosa pine forests. The USDA 

Forest Service General Ecosystem Survey and Terrestrial 

Ecosystem Surveys are limited in their applicability for 

research on songbirds since only Forest Service land is 

included, and since map units are based on potential natural vegetation rather than current vegetation. The data sets 

based on advanced very high resolution radiometer 

(AVHRR) imagery are limited in their applicability, as well. 

They are very coarse-grain, with a resolution of 1 km. Keitt 

et al. (1995) suggest that some details of the Earth Resources Observation Systems (EROS) classification are 

rather suspect from a biogeographic standpoint, and they 

use the USDA Forest Service classification in their analysis of potential habitat patches for the Mexican spotted 

owl. However, the Forest Service classification does not 

distinguish between forest dominated by ponderosa pine 

and forest dominated by Douglas-fir, rendering it inadequate for studies focusing on ponderosa pine forest. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Landscape Dynamics and Considerations 

Table 2. Selected data sets currently available or soon to be available for characterizing landscape patterns lnfluenclng 

songblrds in Southwestern ponderosa pine forests. 

Data set Source of imagery Scale or resolution Availabilitya Referencesb 

USDA Forest Service (Southwestern Region) 

General Ecosystem Survey aerial photography 1 :250,000 currently available 1 

USDA Forest Service Terrestrial 

Ecosystem Surveys aerial photography 1 :24,000 currently available 2 

Vegetative cover types from EROS AVHRR 1 km currently available 3 

USDA Forest Service forest cover types AVHRR 1 Km currently available 4, 5, 6 

AZ Gap Analysis TM 30 m fa11 1997 7 

NM Gap Analysis TM 30 m currently available 8, 9 

a Currently available refers to data sets available as of August 1996. 

References: 1. USDA Forest Service (1989); 2. USDA Forest Service (1986); 3. Loveland et al. (1991); 4. Evans and Zhu (1993); 5. Powell et al. (1993); 6. Zhu and Evans 

(1 992); 7. K. Thomas, personal communication; 8. Muldavin (1994); 9. 6. Thompson, personal communication. 

The Arizona and New Mexico Gap Analysis data sets 

will provide a valuable addition to the spatial data available for landscape ecological studies of songbirds in ponderosa pine forests. Since they are based on Landsat thematic mapper (TM) imagery with a 30-m resolution, 

though, they will be somewhat limited in their usefulness 

for addressing questions requiring very detailed, finegrain data on forest composition and structure. The development of spatial data sets with a relatively high resolution, on the order of 1 m, would provide an extremely 

useful resource for studies on the effects of fine-grain forest attributes on songbirds in the Southwest. 

McGarigal and Marks (1995) have published a computer 

program called FRAGSTATS that provides researchers 

with a powerful tool for quantifying landscape composition and configuration. Versions of FRAGSTATS are available for use with either vector or raster image files. 

FRAGSTATS computes a comprehensive array of landscape metrics including area metrics, patch size metrics, 

edge metrics, shape metrics, core area metrics, nearest 

neighbor metrics, patch diversity metrics, and contagion 

and interspersion metrics. The accompanying documentation includes a thorough description of each metric, including mathematical definitions and a discussion of each 

metric's ecological applications and limitations (McGarigal 

and Marks 1995). 

Fine-Scale Studies 

needed to determine the effects of vegetation species composition, tree size and age class, density of overstory and 

understory vegetation, and fire and grazing history on 

songbird diversity and abundance at the patch level (Hall 

et al. and Finch et al., this volume). Such information will 

be useful for managing forest patches (for example, forest stands) to maintain local songbird diversity and 

abundance. 

In addition, research is needed to determine the extent 

to which individual species are obligate users of ponderosa pine forest. Many songbird species are known to occur in ponderosa pine forest. Some species, such as Grace's 

warbler, appear to be ponderosa pine specialists and may 

require the presence of ponderosa pine forest to survive 

and reproduce (Hall et al., this volume). Other species, 

such as the mountain chickadee, appear to be forest generalists and may be able to thrive in a variety of forest 

types. Still other species, such as the American robin, appear to be extreme generalists and are frequently found 

in a wide variety of forest and non-forest habitats. Clearly, 

individual songbird species can differ greatly in their habitat requirements, and research is needed to elucidate the 

specific habitat requirements for songbirds found in ponderosa pine forests. Information is needed on the extent 

to which individual songbird species require ponderosa 

pine habitat in the breeding season, during migration, and 

as winter residents. 

The degree to which songbird species are ponderosa 

pine specialists versus broader habitat generalists has 

potengal implications for the scale at which those species 

respond to spatial heterogeneity. Ponderosa pine specialists are likely to respond to spatial heterogeneity at a finer 

Although studies of the relationships between habitat scale than habitat generalists. For example, Grace's warcharacteristics and songbird species' richness and abun- blers may be more sensitive than American robins to difdance have been carried out at the individual patch level ferences in tree size and age class, density of overstory 

in Southwestern ponderosa pine forests, more research is and understory vegetation, and grazing intensity within 

needed to clarify these relationships. More research is a ponderosa pine forest. Such hypotheses need to be tested 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 139 
Chapter 7 

in field studies that compare the responses of habitat specialists and generalists to different fine-scale patterns of 

spatial heterogeneity. This type of study will likely reveal 

indicator species (presumably habitat specialists) useful 

for monitoring ponderosa pine forest habitat quality. 

Ponderosa pine specialists also undoubtedly differ from 

habitat generalists in their responses to broad-scale patterns of spatial heterogeneity. For a Grace's warbler, a series of ponderosa pine forests separated by pinyon-juniper woodland might appear to be a fragmented landscape. 

For an American robin, however, the same landscape may 

appear relatively continuous. Understanding the finescale 

habitat requirements of individual species is an important element in understanding the responses of those species to spatial patterns at broader scales. 

Intermediate-Scale Studies 

In addition to studies at the patch level in which individual patches represent independent data points, studies at the landscape level in which landscapes represent 

independent data points are needed to examine the relationships between landscape characteristics and songbird 

distribution and abundance. Examples of such studies 

carried out in other regions include a study by McGarigal 

and McComb (1995) in mixed-conifer forest in the central 

Oregon Coast Range, and a study by Evans (1995) in 

mixed-conifer forest in west-central Idaho. In both studies, landscapes were defined at a scale of several hundred 

hectares and chosen to represent a wide spectrum of spatial patterns reflecting different forest management regimes. McGarigal and McComb (1995) used groundtruthed aerial photographs for baseline data on spatial 

attributes, while Evans (1995) used a ground-truthed timber strata map generated from a Payette National Forest 

timber inventory. In both studies, FRAGSTATS (McGarigal 

and Marks 1995) was used to compute measures of landscape composition and configuration. 

McGarigal and McComb (1995) and Evans (1995) both 

found significant relationships between several measures 

of landscape composition and configuration and the abundance of one or more songbird species. Interestingly, 

McGarigal and McComb (1995) found that for species 

strongly associated with a particular patch type at the 

patch level, the relationships between abundance and the 

amount of preferred patch type present at the landscape 

level varied greatly. McGarigal and McComb's (1995) 

study supports the idea that different processes occur at 

different spatial scales, and that relationships seen at the 

patch level cannot necessarily be extrapolated over landscapes. 

Large-Scale Studies 

Research is also needed at a relatively large scale of 

hundreds to thousands of square kilometers to determine 

patterns of songbird distribution and abundance and shed 

light on ecological processes at this scale. Ecological interacti~ns between individuals of a given species and biotic and abiotic factors in the environment are likely to 

vary across the range of that species. To understand the 

ecology of a species, one must understand ecological processes occurring throughout its range. Thus, to fully understand the ecology of songbirds in Southwestern ponderosa pine forests, one must understand ecological 

processes occurring across the ranges of these species. 

At large spatial scales, ponderosa pine forests in the 

Southwest tend to occur within "Sky Islands" of mountain forest surrounded by seas of arid grassland and desert 

(DeBano et al. 1995; Gehlbach 1981). One area of potential 

interest in studying songbirds in these forests is the area 

of metapopulation dynamics. Metapopulations are groups 

of two or more populations connected by infrequently 

dispersing individuals, and they typically occur when 

populations occupy areas of suitable habitat separated by 

areas of unsuitable habitat (Hanski and Gilpin 1991). Some 

metapopulations may exhibit "source-sink" characteristics 

(Brawn and Robinson 1996; Howe et al. 1991; Pulliam 1988; 

Pulliam and Danielson 1991). In these cases, it is believed 

that individuals from source populations, in which productivity exceeds mortality, disperse to sink populations, which 

would go locally extinct in the absence of such migration. 

Little is known about the extent to which songbird species in Southwestern ponderosa pine forests exhibit 

metapopulation dynamics. Given the fragmented patterns 

of ponderosa pine forest found at large spatial scales in 

the Southwest, it is likely that at least some songbird species found in this habitat exist as metapopulations. However, the degree to which a given species exists as a 

metapopulation is no doubt influenced by the habitat preferences and requirements of the species and the extent to 

which it can disperse through unsuitable habitat. Overall, one would predict that ponderosa pine specialists, such 

as Grace's warbler, would exhibit very different metapopulation dynamics than broader forest generalists, such 

as the mountain chickadee. Mountain chickadees may in 

turn exhibit very different metapopulation dynamics than 

extreme habitat generalists, such as the American robin. 

Likewise, the nature of source-sink dynamics within 

metapopulations undoubtedly varies from species to species. For some species, ponderosa pine forest may represent source habitat in which productivity is relatively high. 

For other species, ponderosa pine forest may represent 

sink habitat in which mortality and emigration exceed 

productivity. Source-sink dynamics are further compliUSDA Forest Service Gen.Tech. Rep. RM-GTR-292. 1997 
Landscape Dynamics and Considerations 

cated in migratory species by the fact that some areas may 

be unimportant for breeding but critical as stopover sites 

during migration or as wintering habitat. 

Attempting to understand metapopulation dynamics 

is an ideal example of an endeavor that requires research 

at multiple spatial scales. Studies at fine scales are needed 

to determine exactly how the species in question uses different habitat types. Studies at intermediate scales are 

needed to learn more about habitat requirements, including how landscape composition and configuration affect 

habitat selection. Studies at larger scales are needed to 

determine overall patterns of habitat availability, how 

habitat use varies throughout the range, and how patterns 

of habitat availability and use relate to metapopulation 

dynamics. For migratory species, information at each spatial scale is needed for breeding areas, for stopover sites 

used during migration, and for wintering habitat. 

One key aspect of understanding the population dynamics of a species is understanding dispersal patterns 

of individuals through different habitat types. We know 

that most songbirds are capable of traveling great distances (many migrate to the tropics for the winter). However, vagility, or the physical ability of a species to move, 

should not be equated with dispersal, or the movement 

of individuals to new areas to settle there and breed 

(Villard et al. 1995). Little is known about dispersal in songbirds. Some studies (Drilling and Thompson 1988; Holmes 

and Sherry 1992; Kendeigh 1941) suggest that typical dispersal distances for adults in some species of songbirds 

may be less than 350 m. However, these studies provide 

limited data for a small number of species. Even less is 

known about dispersal in first-year songbirds, that is, how 

far first-year birds tend to nest from their birth sites. Greenwood and Harvey (1982) suggest that the median firstyear dispersal for both sexes is usually less than 10 territories away from the birth site. However, Villard et al. 

(1995) argue that this generalization may not be valid since 

recapture rates of songbirds banded as nestlings are usually lower than 10 percent. In forest patches of central Illinois, Robinson (1992) observes that songbirds have very 

low reproductive success, and he suggests that populations in the area may be maintained by individuals dispersing from forests over 200 km away. 

To date, no studies have been published estimating dispersal distances for songbirds in ponderosa pine forests 

in the Southwest. Information on dispersal distances could 

potentially be gathered through extensive banding operations and attempts at recapture across large areas. Another 

alternative would be to identify isolated patches in which 

one or more species have been extirpated due to stochastic processes, forest fires, or human activities such as logging, and then survey those patches to determine whether 

those species reappear over time. If those species do reappear, this would suggest that they were able to disperse 

from an area at least as far away as the nearest suitable 

habitat (Villard et al. 1995). Such studies would be especially useful when the areas of nearest suitable habitat are 

a considerable distance away (for example, in another Sky 

Island), as they might provide insights into maximum dispersal distances for songbirds over different habitat types. 

Spatial data sets from the Arizona and New Mexico Gap 

Analysis projects should provide information useful for 

large-scale studies on songbirds in Southwestern ponderosa pine forests (table 2). To adequately study most ecological patterns and processes important for songbirds in 

ponderosa pine forests, though, analyses of spatial data 

from imagery will need to be accompanied by field investigations. This will likely present some logistical challenges 

at scales of hundreds to thousands of square kilometers. 

Nonetheless, data from imagery are generally of little use 

unless they are ground-truthed and closely linked with 

data collected in the field. The collection of field data across 

large spatial scales may be facilitated by collaboration 

among researchers and by the careful selection of field 

sites based on high-quality imagery. 

Habitats and Species of Special 

Concern 

Because of the relatively small area of old-growth ponderosa pine forests remaining in the Southwest and economic pressures to harvest these forests, research into 

songbird responses to landscape characteristics of oldgrowth ponderosa pine forests at multiple scales should 

be a top priority. At the patch level, more research is 

needed to determine exactly how songbirds use oldgrowth ponderosa pine forests and the extent to which 

they depend on them. At larger landscape levels, research 

is needed to determine how the proportion and spatial 

configuration of old-growth ponderosa pine forest in a landscape influences songbird distribution and abundance. 

Research on songbird responses to landscape composition and configuration at multiple scales is needed that 

considers both overall songbird diversity and the abundance of individual species. Measuring the local diversity of songbird species in an area provides insight into 

the ability of that area to support a variety of different 

kinds of songbirds. However, from a regional perspective, 

the number of species in a given area may not be as important as which species are present. For example, a 

clearcut patch may be found to have a relatively high diversity of songbird species, but those species may be common throughout the region. Thus, widespread clearcutting 

in the region might produce areas of high local species 

diversity while dramatically reducing overall regional 

diversity. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 7 

Studies that focus on individual songbird species are 

necessary for understanding the relationships between 

individual species and different types of habitat and for 

gaining insights into population and metapopulation dynamics. Landscape-level studies focusing on those songbird species most vulnerable to local extirpation or 

rangewide extinction are especially urgent. No such studies have been carried out, and landscape-level information is needed to inform management decisions affecting 

regional avian diversity and the long-term viability of 

those species. 

A list of bird species on managed ponderosa pine Breeding Bird Survey routes in Arizona and New Mexico whose 

populations have been declining is provided in Chapter 4 

of this volume (from Miller 1992), as is a list of bird species found in ponderosa pine forests ranked as being of 

high or moderate concern by the Arizona and New Mexico 

Partners in Flight programs. These lists offer a starting 

point for identifying target species for landscape-level 

studies in Southwestern ponderosa pine forests. 

Typically, landscape-level studies of songbirds in other 

regions have involved sampling all songbird species encountered across different landscapes using standardized 

techniques. In many studies, rare species were not considered in the analysis of abundance data because they 

did not lend themselves well to the statistical methods used 

(for example, Evans 1995; Hagan et al. 1996; Knick and 

Rotenberry 1995; McGarigal and McComb 1995; Rosenberg 

and Raphael 1986). To overcome this problem in Southwestern ponderosa pine forests, research must be carried out over 

broad enough spatial and temporal scales that sufficient data 

on rare species are gathered for statistical analysis. 

Rare species form a critical component of bird communities. In most studies of bird communities, a small number of species are found at all or most sites while many 

species occur at only a few (for example, Evans 1995; 

Hansen et al. 1995; Hejl and Woods 1991; Rosenberg and 

Raphael 1986; Verner and Larson 1989). Landscape-level 

research that focuses on rare species is needed to gather 

more information about these species and to provide a 

scientific basis for managing rare species and their habitats. Maintaining viable populations of rare species is essential for maintaining overall avian diversity in the Southwest, as well as for maintaining healthy, intact communities 

and ecosystems. 

Acknowledgments 

We thank John Dunning, Natasha Kotliar, Kevin 

McGarigal, Deborah Finch, Joseph Ganey, William Block, 

and three anonymous reviewers for comments that greatly 

improved this manuscript. 

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USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 8 

Summary 

William M. Block, Deborah M. Finch, Joseph L. Ganey, and William H. Moir 

Most ornithological studies in Southwestern ponderosa 

pine forests have yielded results that are applicable only 

to the specific location and particular conditions of the 

study areas (for example, Green 1979 and Hurlbert 1984). 

In addition, varying interpretation of similar study results 

by investigators has limited our ability to extend or synthesize research results from Southwestern ponderosa 

pine forests beyond the scope of any individual study. In 

studies that address similar questions and have similar 

results, broader inferences are possible. 

Isolated studies of selected aspects of songbird ecology 

will not provide the level of resolution required to answer 

complex research questions and management problems. 

Therefore, decision makers should review our research 

recommendations and commit adequate financial and 

institutional support to incorporate them into a coordinated research program that systematically addresses 

these research needs. Developing management approaches to research needs that also meet societal demands 

will only occur when the USDA Forest Service, USDI Fish 

and Wildlife Service, state resource agencies, public advocacy groups, and other organizations agree that a more 

comprehensive understanding of ponderosa pine forest 

ecology is mandatory for management of Southwestern 

ponderosa pine forests and their avifauna. 

Ponderosa Pine Forest Ecology 

Ponderosa pine forests today differ drastically from 

those before European settlement of the Southwest 

(Covington and Wagner 1996; Moir et al., this volume). 

Many of these changes resulted from past land-use activities, primarily since European settlement (Raish et al, 

this volume; Scurlock and Finch, this volume). The foremost activities leading to forest change include logging, 

fuelwood harvest, fire suppression, livestock grazing, and 

urban development (Finch et al., this volume; Raish et al, 

this volume; Scurlock and Finch, this volume). The singular, synergistic, and cumulative impacts of these land 

uses have resulted in overstocked forests that exhibit 1) 

size-class distributions skewed toward smaller trees, 2) 

unnaturally high levels of disease and pathogens, 3) high 

susceptibility to catastrophic crown fires, 4) depleted 

woody and herbaceous understories, and 5) altered ecological relationships and ecosystem processes (Moir et al., 

this volume). 

If we hope to evaluate population changes of birds inhabiting ponderosa pine forests, we must understand how 

their habitats have changed. Our knowledge of presettlembnt or reference ponderosa pine forests is limited to 

the results of retrospective studies, archaeological records, 

and exploration narratives (for example, Covington and 

Wagner 1996; and Scurlock and Finch, this volume). Although these descriptions provide useful models of 

presettlement forest patterns, the models are general, lacking detail about the range of variation that existed before 

intensive forest management (Reynolds et al. 1996). 

Presettlement or reference states for Southwestern forests 

are typically inferred from conditions existing in the late 

1800s (Covington and Moore 1994). This assumes that historical conditions recorded during this time period are 

representative of prehistoric and Mexican periods, but as 

Scurlock and Finch (this volume) described, American 

Indians and Spanish people used Southwestern forests 

and wildlife to varying degrees before Anglo-American 

colonization of the Southwest through the 1800s. Therefore, we question the reliance on the late 1800s as the appropriate period for inferring reference forest conditions 

demonstrating minimal human impact. 

Ponderosa pine occupies a gradient from the upper elevation of the pinyon-juniper woodland to mixed-conifer 

forests. Most knowledge of presettlement conditions is 

derived from studies conducted within the mid-elevation 

zone (between pinyon-juniper and mixed-conifer) where 

ponderosa occurs as a climax species. Researchers generally agree that xerophytic ponderosa pine forests were 

more open with clumps of pine trees interspersed among 

grassy openings. These conditions were maintained by 

low-intensity ground fires every 2 to 12 years that limited 

tree regeneration and dense forests (Moir et al., this volume). Given these conditions and disturbance regimes, 

much of the presettlement xerophytic pine forest probably tended toward older, mature conditions (Covington 

and Moore 1994). Descriptions of mesophytic forests (for 

example, mixed conifer) where ponderosa pine is a sera1 

species are less available, but many of these forests were 

more open before 1880 (Moir et al., this volume). 

Our ability to characterize existing ponderosa pine forests is also somewhat limited. We have detailed information on forest structure and composition for some areas, 

but information is limited for most. From what we do 

know, much of the existing ponderosa pine forests are relatively dense because small, relatively young (do0 years 

old) trees have proliferated in response to human use of 

forested lands. Logging, fuelwood harvest, and cataUSDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Chapter 8 

strophic fire have reduced the numbers of large, mature 

ponderosa pine trees and snags over time (Raish et al., 

this volume). Areas where the forest was originally a 

mosaic of tree clumps and grassy openings have become 

continuous tree canopies as trees have invaded these openings. Fire regimes and disease pathways have been altered, 

rendering these forests at far more risk than they were 

historically. Where fire, insects, and disease once played 

key roles in maintaining forests, they can now devastate 

forests. 

We are also observing shifts in the composition of these 

forests as a result of past forest management. In some 

ponderosa pine stands, the number of shade-tolerant conifers is increasing, moving the classification of some 

stands from ponderosa pine to mixed-conifer (Johnson 

1994a). In existing mixed-conifer forests, an emphasis on 

harvesting mature ponderosa pine trees over other conifer species may be altering both stand structure and composition in favor of more shade-tolerant conifers such as 

Douglas-fir and white fir (USDI 1995). 

A cornerstone to conserving avian populations in ponderosa pine forests is acquiring more detailed information about past and current forest conditions. Published 

research and existing knowledge (this volume) provide a 

good foundation from which we can proceed, but significant information gaps remain. In particular, we must understand the range of variation in key forest attributes both 

in reference ponderosa pine forests and in the forests that 

exist today. Managing ponderosa pine forests for one ecological condition may not provide the variation in conditions needed to support the variety of birds native to 

Southwestern pine forests (Miller 1996). Also required is 

the information and technology needed to evaluate forest 

conditions over large geographic areas. The ability to 

quantify and model spatial relationships of vegetative 

conditions, especially at the landscape and regional scales, 

is critical to understanding the dynamics of ponderosa 

pine ecosystems and evaluating areas in greatest need of 

remedial management actions. 

Songbird Ecology 

Most insightful studies of the ecology of ponderosa pine 

birds have been conducted within the past 40 years. These 

studies have been largely descriptive, although some 

small-scale experiments have been conducted. The most 

extensive descriptive study examined bird-habitat relationships within 23 stands representing gradients of ecological conditions in ponderosa pine and pine-oak forests 

of northern Arizona (Rosenstock 1996). This work with 

major studies by Szaro, Brawn, Blake, Balda, and others 

(for example, T. Martin's study in progress through the 

Montana Cooperative Wildlife Research Unit, University 

of Montana) provides the basis for much of our current 

knowledge of songbird community ecology in Southwestern ponderosa pine forests (Finch et al., this volume; Hall 

et al., this volume). Knowledge gaps not addressed by 

community-level studies are captured to some extent by 

single-species studies conducted by investigators such as 

Marzluff and Martin (Marzluff, this volume; Finch et al., 

this volume; Hall et al., this volume). 

Because most published studies of passerines are relatively recent, their results largely reflect ecological relationships in forests altered by human activities over the 

past century. Although archaeological records from prehistoric periods and historical ornithological accounts 

from expeditions and collections exist for the Southwest 

(Scurlock and Finch, this volume), these records document 

mostly presence and absence of bird species rather than 

avian abundances. Therefore, bird use of ponderosa pine 

forests reported in contemporary studies cannot be readily 

compared to historical accounts or archaeological finds. 

Consequently, we do not know if patterns of abundance 

and species composition of birds that we see today are 

similar to those of presettlement forests. Because the 

Southwest has undergone extensive climatic changes such 

as warming over geologic time, contemporary avifaunas 

in Southwestern ponderosa pine forests likely differ from 

prehistoric or historical avifaunas in response to natural 

forest changes alone (Johnson 1994b). That the Southwest 

was settled by different cultural groups at different periods of time, each group using forest and avian resources 

to different extents (Scurlock and Finch, this volume), further confounds interpretation of temporal and spatial 

changes in avifaunas. 

If we assume, however, that the strongest or most consistent relationships that we detect in contemporary studies also existed in the past, then it could be instructive to 

evaluate whether habitat resources essential for specific 

bird species were available in presettlement forests. We 

could then speculate whether temporal changes in resource distributions or quantities would have been beneficial or detrimental to species' populations. For example, 

species that rely on large trees for an important aspect of 

their life history (such as nesting) may have been more 

abundant in the past when large trees were more abundant, whereas species that favor dense stands may have 

been less abundant historically. 

Cavity-nesting species are perhaps the most studied 

group of birds in the Southwest (Balda 1975; Cunningham 

et al. 1980; Ffolliot 1983; Brawn and Balda 1983, Rosenstock 

1996). Collectively, these studies emphasize the importance of snags, particularly large snags, as potential nesting substrates for these species. Results of Brawn's (1985) 

experimental research on secondary cavity-nesting birds 

and Rosenstock's (1996) observational research on both 

primary and secondary cavity nesters concur that snags 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Summary 

and nest substrates are limiting factors for many of these 

species. Miller's (1992) analysis of Breeding Bird Survey 

(BBS) data suggests that populations of the hairy woodpecker, acorn woodpecker, violet-green swallow, whitebreasted nuthatch, pygmy nuthatch, mountain chickadee, 

and mountain bluebird are declining in the Southwest. If 

these declines are indeed real, then loss of snags that provide nest, foraging, and perch sites could be a contributing 

or even a primary factor explaining declining populations. 

The loss of large trees in many ponderosa pine forests 

has also likely impacted populations and habitats of numerous species. Rosenstock (1996) found positive relationships between the relative abundance of large trees and 

breeding populations of violet-green swallows, brown 

creepers, house wrens, chipping sparrows, pygmy 

nuthatches, and northern flickers. All of these species except the chipping sparrow are bark-foraging species or 

require snags for nesting. Large trees may provide habitat for many arthropod prey of bark-foraging birds, and 

these bark-foraging birds may be morphologically 

adapted to forage more efficiently on the bark furrows of 

larger trees (Richardson 1942). For species such as the chipping sparrow and perhaps Grace's warbler, large trees 

provide elevated song posts and substrates for their opencup nests. Thus, the loss of large trees not only curtails 

the sustained supply of large snags and nest cavities but 

may also reduce foraging substrates, song perches, and 

substrates for open-cup nests. 

Changes to the forest understory, mainly the loss of 

structural and floristic diversity, have also altered habitats of a number of species. Gambel oak is an important 

understory component in pine-oak forests (Rosenstock 

1996), and aspen is an important component of some early 

successional ponderosa pine forests. Unlike pines, large 

oaks and aspens often have natural or excavated cavities 

while still live. Characteristics of these cavities appear to 

be favored by some bird species over cavities in pine snags 

(Finch et al., this volume). Gambel oak provides acorn 

mast, and arthropods found on oaks add to the diversity 

of prey for insectivorous birds. We are observing loss of 

large Gambel oaks to fuelwood harvest and loss of aspen 

to pine succession in fire-excluded forests. Increased competition with pines for light as forest canopy cover increases may also explain declines of these deciduous trees. 

Further, heavy browsing by wildlife and livestock may 

be limiting regeneration of oak, aspen, and shrubs to replace those lost by natural or human causes (USDI 1995). 

Grasses, forbs, and shrubs provide cover for groundforaging and ground-nesting species. They also provide 

a variety of seeds, fruits, and nectar for granivorous (such 

as juncos, towhees, sparrows), frugivorous (such as 

thrushes), and nectivorous (such as hummingbirds) species. Since 1880, these herbaceous understories have been 

heavily impacted by livestock, elk, increased tree densities, and altered fire regimes. Undoubtedly, these changes 

have affected the avifauna. Reductions in the amounts of 

seeds and fruits may be particularly important during the 

winter, when these foods are generally more available than 

arthropods. 

Studies should continue to emphasize habitat and population ecology but must provide greater consideration of 

geographic variation, seasonality, spatial scale, and population demographics. Past management activities have 

reduced the amount of mature/old-growth ponderosa 

pine:forest in the Southwest and the openness of stands. 

Older forests and open forests provide unique conditions 

used by various species (Siege1 1989, Finch et al, this volume). Researchers have identified some general habitat 

correlates for birds in late-successional forests, but additional research-especially experimental-that details the 

ultimate and proximate factors underlying avian selection of different ponderosa pine habitats could help to 

identify key forest attributes that might be emphasized in 

future forest management. New research should examine 

bird-habitat relationships in different ponderosa pine 

types, successional stages, and patch sizes across a gradient of spatial scales and management situations (commercial forests, wilderness areas, research natural areas, experimental forests). Research should also identify key 

site-level characteristics. At larger landscape scales, for 

example, bird-habitat relationships should consider patch 

size and shape, distance between patches, number of 

patches, and landscape mosaic patterns (Rich and 

Mehlhop, this volume). 

Published information on bird-habitat relationships is 

limited both spatially and temporally. As noted by Rich 

and Mehlhop (this volume), knowledge of habitat relationships and population characteristics of ponderosa pine birds 

at the landscape level is virtually nonexistent for the Southwest. Many earlier studies suffer from little or no replication (number of sample plots within a similar condition 

or treatment), restricting the level of inference possible 

from the results. Also, most studies were relatively shortterm (1-4 years) and were typically restricted to the breeding season. In addition, most breeding bird studies did 

not evaluate reproductive success or survival rates in relation to habitat elements. As a result, the full range of 

habitat use by resident species has not been sampled; habitat use by species that do not occupy Southwestern ponderosa pine forests during the breeding season (for example, most wintering and many migrating birds) has 

rarely been studied; temporal variation in bird communities is not well understood (Gaud et al. 1986; Hejl and 

Beedy 1986; Hall et al., this volume); and avian demographic responses to habitat variation need further study. 

Thus, our knowledge of habitat associations of birds in 

ponderosa pine is a credible start but is far from what we 

require to describe desired conditions to land managers. 

Existing information on population trends and the 

population ecology of ponderosa pine birds provides good 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 147 
Chapter 8 

baseline information but leaves many questions unanswered. Results from analyses of BBS and Christmas Bird 

Count (CBC) data, despite their weaknesses, can be used 

as a starting point to focus future monitoring and research 

efforts (which is indeed their intent). A logical start would 

be to increase the number of samples in ponderosa pine 

forests for both BBS and CBC and to allocate samples 

throughout the range of conditions found in these forests. 

Further, results from BBS or CBC data could be used as a 

basis for more intensive sampling efforts (see also Manley 

et al. 1993). For example, Miller's (1992) preliminary analysis of BBS data suggests that more species have declined 

than have increased in abundance over the past 30 years. 

Greater effort should be devoted to monitoring bird populations exhibiting these perceived declines. This more intensive monitoring should not be restricted to measures 

of absolute or relative abundance, but should also include 

estimates of other population parameters such as survival, 

reproduction, or turnover rates. Likely, research will be 

needed to determine which population parameter is the 

most sensitive index of population status prior to initiating intensive monitoring efforts. 

Effects of Land-Use Activities 

Numerous types of land and natural resource use have 

the potential of altering bird habitats, leading to spatial 

and temporal changes in bird populations (Rotenberry et 

al. 1995; Saab et al. 1995; Thompson et al. 1995). The primary current land uses discussed in this volume include 

timber harvest, fire, fire suppression, grazing by wildlife 

and livestock, recreation, and urbanization. At least three 

major factors complicate a study addressing the effects of 

any of these factors. The first is that natural events such 

as climate, succession, and numerous stochastic disturbances occur simultaneously with human impacts. Separating effects of natural events from human activities is 

extremely difficult. Second, where human activities occur, more than one type of activity usually takes place. 

For example, many forests that have undergone timber 

harvest have also been subjected to fire suppression and 

livestock grazing. Thus, the real effects of land use are 

likely synergistic rather than the results of any one factor 

acting singly. Third, effects of activities can become additive or even multiplicative over time. These cumulative 

effects, coupled with synergistic effects and effects of natural events, create a difficult and complicated puzzle to 

solve. That has not prevented researchers from attempting to address these questions in the past, nor should it 

dissuade researchers from doing so in the future. Limiting the number of variables under study can help to reduce the complexity of a study, and developing cooperative research partnerships to conduct studies that address 

interactions among land uses may be the key to interpreting complex bird-habitat relationships. Regardless of how 

studies might be approached, understanding interactive 

cause-effect relationships of land use is critical for future 

management of Southwestern ponderosa pine forests and 

the conservation of the associated avifauna. 

Observational studies are basically correlative and may 

not elucidate cause-effect relationships. Although the studies revlewed in this book have provided useful information, the interpretations that we have drawn from them 

are limited. The effects of various land uses, singly and in 

combination, are best studied using well-designed experiments. The need for experiments to understand the effects of land management on specific ecosystem attributes 

(including birds) is not a new concept (see Eberhardt and 

Thomas 1991; James and McCulloch 1995; USDI 1995). 

Such studies are rarely conducted because costs and logistical obstacles associated with implementing large-scale 

forest manipulations limit their application. 

We recognize that the design and implementation of 

experiments is a daunting challenge (Carpenter et al. 1995). 

Granted, we can develop educated guesses based on available evidence as to how particular land uses might affect 

bird habitats, populations, and perhaps community dynamics, but we can rarely assign levels of assurance that 

our guesses are correct. Given that such studies would 

need to be both well replicated and conducted at large 

spatial scales, success of implementing experiments requires commitment and collaboration by public participants, resource-management agencies, and researchers. 

Treatments such as logging, fire, and grazing manipulations would need to be implemented by management 

agencies, following experimental designs developed in 

cooperation with researchers. Numerous opportunities 

exist to plan and design management treatments that allow for the implementation of research experiments (Carpenter et al. 1995). Taking advantage of these opportunities would resolve many key issues on forest passerine 

ecology. 

Literature Cited 

Balda , R. P. 1975. The relationship of secondary cavity 

nesters to snag densities in western coniferous forests. 

USDA Forest Service Southwestern Region, Wildlife 

Habitat Technical Bulletin 1, Albuquerque, New Mexico, 

USA. 

Brawn, J. D. 1985. Population biology, community structure, and habitat selection of birds in ponderosa pine 

forest habitat. Ph.D. thesis, Northern Arizona University, Flagstaff, Arizona, USA. 

148 USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Summary 

Brawn, J. D., and R. P. Balda. 1983. Use of nest boxes in 

ponderosa pine forests. Pages 159-164 in J. W. Davis, G. 

A. Goodwin, and R. A. Ockenfiels, editors. Snag habitat management: proceedings of a symposium. USDA 

Forest Service General Technical Report RM-99, Fort 

Collins, Colorado, USA. 

Carpenter, S. R., S. W. Chisholm, C. J. Krebs, D. W. 

Schindler, and R. W. Wright. 1995. Ecosystem experiments. Science 269:324-327. 

Covington, W. W., and M. M. Moore. 1994. Southwestern 

ponderosa forest structure: changes since Euro-American settlement. J. For. 92(1):3947. 

Covington, W. W., and P. K. Wagner, tech. coords. 1996. 

Conference on adaptive ecosystem restoration and management: restoration of Cordilleran conifer landscapes 

of North America. USDA Forest Service General Technical Report RM-278, Fort Collins, Colorado, USA. 

Cunningham, J. G., R. P. Balda, and W. S. Gaud. 1980. Selection and use of snags by secondary cavity nesters of 

ponderosa pine forest. USDA Forest Service Research 

Paper RM-222, Fort Collins, Colorado, USA.. 

Eberhardt, L. L., and J. M. Thomas. 1991. Designing environmental field studies. Ecological Monographs. 61: 

53-73. 

Ffolliott, P. F. 1983. Implications of snag policies on management of Southwestern ponderosa pine forests. Pages 

28-32 in J. W. Davis, G. A. Goodwin, and R. A. 

Ockenfiels, editors. Snag habitat management: proceedings of a symposium. USDA Forest Service General 

Technical Report RM-99, Fort Collins, Colorado, USA. 

Gaud, W. S., R. P. Balda, and J. D. Brawn. 1986. The dilemma of plots or years: a case for long-term studies. 

Pages 223-228 in J. Verner, M. L. Morrison, and C. J. 

Ralph, editors. Wildlife 2000: modeling habitat relationships of terrestrial vertebrates. University of Wisconsin 

Press, Madison, Wisconsin, USA. 

Green, R. H. 1979. Sampling design and statistical methods for environmental biologists. John Wiley and Sons, 

New York, USA. 

Hejl, S. J. and E. C. Beedy. 1986. Weather-induced variation in the abundance of birds. Pages 241-244 in J. 

Verner, M. L. Morrison, and C. J. Ralph, editors. Wildlife 2000: modeling habitat relationships of terrestrial 

vertebrates. University of Wisconsin Press, Madison, 

Wisconsin, USA. 

Hurlbert, S. H. 1984. Pseudoreplication and the design of 

ecological field experiments. Ecological. Monographs 

54:187-211. 

James, F. C., and C. E. McCulloch. 1995. The strengths of 

inferences about causes of trends in populations. Pages 

40-51. in T.E. Martin, and D.M. Finch, editors. Ecology 

and management of neotropical migratory birds. Oxford University Press, New York, USA 

Johnson, M. 1994a. Changes in Southwestern forests: stewardship implications. Journal of Forestry 92(12):16-19. 

Johnson, N. K. 1994b. Pioneering and natural expansion 

of breeding distributions in western North American 

birds. Studies in Avian Biology 15:2744. 

Manley, P. N., W. M. Block, F. R. Thompson, G. S. Butcher, 

C. Paige, L. H. Suring, D. S. Winn, D. Roth, C. J. Ralph, 

E. Morris, C. H. Flather, K. Byford. 1993. Guidelines for 

monitoring populations of neotropical migratory birds 

on National Forest Systems lands. USDA Forest Service, 

Washington, D.C., USA. 

Miller, R. 1992. Preliminary results from breeding bird 

survey data estimates of trends in bird populations in 

or near managed ponderosa pine in the Southwest. 

Unpublished report. Arizona Department of Game and 

Fish, Flagstaff, Arizona, USA. 

Miller, R. 1996. The need for diversity and acceptable risk. 

Pages 19-24 in W. Covington and P. K. Wagner, technical coordinators. Conference on adaptive ecosystem 

restoration and management: restoration of Cordilleran conifer landscapes of North America. USDA Forest 

Service General Technical Report RM-278. Fort Collins, 

Colorado, USA. 

Reynolds, R. T., W. M. Block, and D. A. Boyce Jr. 1996. 

Using ecological relationships of wildlife as templates 

for restoring Southwestern forests. Pages 34-42 in W. 

Covington and P. K. Wagner, technical coordinators. 

Conference on adaptive ecosystem restoration and management: restoration of Cordilleran conifer landscapes 

of North America. USDA Forest Service General Technical Report RM-278. Fort Collins, Colorado, USA. 

Richardson, F. 1942. Adaptive modifications for tree-trunk 

foraging in birds. University of California Publications 

in Zoology 46:317-368. 

Rosenstock, S. S. 1996. Habitat relationships of breeding 

birds in northern Arizona ponderosa pine and pine-oak 

forests. Arizona Game and Fish Department Research 

Branch, Technical Report 23, Phoenix, Arizona, USA. 

Rotenberry, J. T., R. J. Cooper, J. M. Wunderle, and K. G. 

Smith. 1995. When and how are populations limited? 

The roles of insect outbreaks, fire, and other natural 

perturbations. Pages 55-84 in T.E. Martin and D.M. 

Finch, editors. Ecology and management of neotropical 

migratory birds. Oxford University Press, New York, 

USA. 

Saab, V. A., C. E. Bock, T. D. Rich, and D. S. Dobkin. 1995. 

Livestock grazing effects in western North America. 

Pages 311-353 in T.E. Martin and D.M. Finch, editors. 

Ecology and management of neotropical migratory 

birds. Oxford University Press, New York, USA. 

Siegel, J. J. 1989. An evaluation of the minimum habitat 

quality standards for birds in old-growth ponderosa 

pine forests, northern Arizona. M.S. thesis, University 

of Arizona, Tucson, Arizona, USA. 

Thompson, F. R., 111, J. R. Probst, and M. G. Raphael. 1995. 

Impacts of silviculture: overview and management recommendations. Pages 201-219 in T.E. Martin and D.M. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 149 
Chapter 8 

Finch, editors. Ecology and management of neotropical USDI Fish and Wildlife Service. 1995. Recovery plan for 

migratory birds. Oxford University Press, New York, the Mexican spotted owl. Vol. I. USDI Fish and Wildlife 

USA. Service, Albuquerque, New Mexico, USA. 

USDA Forest Service Gen. Tech. Rep. RM-GTR-292. 1997 
Appendix: Birds Referenced in This Book 

Common name Scientific name 

Acorn woodpecker 

American crow 

American dipper 

American goldfinch 

American kestrel 

American robin 

Ash-throated flycatcher 

Baird's sparrow 

Bald eagle 

Band-tailed pigeon 

Barn swallow 

Bell's vireo 

Berylline hummingbird 

Bewick's wren 

Black-billed magpie 

Black-capped chickadee 

Black-capped vireo 

Black-chinned hummingbird 

Black-headed grosbeak 

Black-throated gray warbler 

Black phoebe 

Blue grouse 

Blue-gray gnatcatcher 

Blue grosbeak 

Blue-throated hummingbird 

Brewer's blackbird 

Brewer's sparrow 

Broad-tailed hummingbird 

Brown creeper 

Brown-headed cowbird 

Buff-breasted flycatcher 

Bullock's orioles 

Bushtit 

California spotted owl 

Calliope hummingbird 

Canada jay 

Canyon wren 

Cation towhee 

Cassin's finch 

Cassin's kingbird 

Cedar waxwing 

Chipping sparrow. 

Clark's nutcracker 

Common crow 

Common nighthawk 

Common raven 

Common poorwill 

Cooper's hawk 

Melanerpes formicivorus 

Corvus brachyrhynchos 

Cinclus mexicanus 

Carduelis tristis 

Falco sparverius 

Turdus migratorius 

Myiarchus cinerascens 

Ammodramus bairdii 

Haliaeetus leucocephalus 

Columba fasciata 

Hirundo rustica 

Vireo bellii 

Amazilia beryllina 

Thryomanes bewickii 

Pica pica 

Parus atricapillus 

Vireo atricapillus 

Archilochus alexandri 

Pheucticus melanocephalus 

Dendroica nigrescens 

Sayornis nigricans 

Dendragapus obscurus 

Polioptila caerulea 

Guiraca caerulea 

Lampornis clemenciae 

Euphagus cyanocephalus 

Spizella breweri 

Selasphorus platycercus 

Certhia americana 

Molothrus atrer 

Empidonax fulvifrons 

lcterus bullockii 

Psaltriparus minimus 

Strix occidentalis occidentalis 

Stellula calliope 

Perisoreus canadensis 

Catherpes mexicanus 

Pipilo fuscus 

Carpodacus cassinii 

Tyrannus vociferans 

Bombycilla cedrorum 

Spizella passerina 

Nucifraga columbiana 

Corvus brachyrhynchos 

Chordeiles minor 

Corvus corax 

Phalaenoptilus nuttallii 

Accipiter cooperii 

cordilleran (western) flycatcher ~mpidonax difficilis 

Curve-billed thrasher Toxostoma cun~irostre 

Dark-eyed junco Junco hyemalis 

Common name Scientific name 

Downy woodpecker 

Dusky flycatcher 

Dusky-capped flycatcher 

Eastern bluebird 

Eastern kingbird 

Eastern meadowlark 

Elegant trogon 

European starling 

Evening grosbeak 

Flammulated owl 

Fox sparrow 

Golden-crowned kinglet 

Golden eagle 

Grace's warbler 

Gray flycatcher 

Great horned owl 

Greater peewee 

Greater roadrunner 

Green-tailed towhee 

Hairy woodpecker 

Hammond's flycatcher 

Hepatic tanager 

Hermit thrush 

House finch 

House sparrow 

House wren 

Hutton's vireo 

Killdeer 

Lark sparrow 

Lazuli bunting 

Lesser goldfinch 

Lesser nighthawk 

Lewis' woodpecker 

Lincoln's sparrow 

Loggerhead shrike 

Lucy's warbler 

Mallard 

MacGillivray's warbler 

Magnificent hummingbird 

Merriam's turkey 

Mexican chickadee 

Mexican parrot 

Mexican spotted owl 

Merlin 

Military macaw 

Montezuma quail 

Mountain bluebird 

Mountain chickadee 

Mourning dove 

Northern flicker 

Northern goshawk 

Picoides pubescens 

Empidonax oberholseri 

Myiarchus tuberculifer 

Sialia sialis 

Tyrannus tyrannus 

Sturnella magna 

Trogon elegans 

Sturnus vulgaris 

Coccothraustes vespertinus 

Otus flammeolus 

Passerella iliaca 

Regulus satrapa 

Aquila chrysaetos 

Dendroica graciae 

Empidonax wrightii 

Bubo virginianus 

Contopus pertinax 

Geococcyx californianus 

Pipilo chlorusrus 

Picoides villosus 

Empidonax hammondii 

Piranga flava 

Catharus guttatus 

Carpodacus mexicanus 

Passer domesticus 

Troglodytes aedon 

Vireo huttoni 

Charadrius vociferus 

Chondestes grammacus 

Passerina amoena 

Carduelis psaltria 

Chordeiles acutipennis 

Melanerpes lewis 

Melospiza lincolnii 

Lanius ludovicianus 

Vermivora luciae 

Anas platyrhynchos 

Oporornis tolmiei 

Eugenes fulgens 

Meleagris gallopavo merriami 

Parus sclateri 

Arnazona spp. 

Strix occidentalis lucida 

Falco columbarius 

Ara militaris 

Cyrtonyx montezumae 

Sialia currucoides 

Parus gambeli 

Zenaida macroura 

Colaptes auratus 

Accipiter gentilis 

USDA Forest Service Gen. Tech. Rep. RM-GTR-XXX. 1997 

- - - 

continued on next page 

151 
Appendix 

Common name Scientific name 

Northern mockingbird 

Northern pygmy owl 

Northern woodpecker 

Olive-sided flycatcher 

Olive warbler 

Orange-crowned warbler 

Painted redstart 

Peregrine falcon 

Pileated woodpecker 

Pine grosbeak 

Pine siskin 

Pinyon jay 

Plain titmouse 

Prairie chicken 

Purple martin 

Pygmy nuthatch 

Quetzal 

Red-breasted nuthatch 

Red crossbill 

Red-faced warbler 

Red-naped sapsucker 

Red-tailed hawk 

Red-shafted northern flicker 

Rivoli's hummingbird 

Rock dove 

Rock wren 

Rosy finch 

Rough-winged swallow 

Ruby-crowned kinglet 

Rufous hummingbird 

Sandhill crane 

Savannah sparrow 

Saw-whet owl 

Say's phoebe 

Scarlet macaw 

Scott's orioles 

Scrub jay 

Sharp-shinned hawk 

Solitary vireo 

Song sparrow 

Mimus polyglottos 

Glaucidium gnoma 

Picoides spp. 

Contopus borealis 

Peucedramus taeniatus 

Vermivora celata 

Myioborus pictus 

Falco peregrinus 

Dryocopus pileatus 

Pinicola enucleator 

Carduelis pinus 

Gymnorhinus cyanocephalus 

Parus inornatus 

Tympanuchus spp. 

Progne subis 

Sitta pyhmaea 

Pharomachrus spp. 

Sitta canadensis 

Loxia curvirostra 

Cardellina rubrifrons 

Sphyrapicus varius nuchalis 

Buteo jamaicensis 

Colaptes auratus 

Eugenes fulgens 

Columba livia 

Salpinctes obsoletus 

Leucosticte arctoa 

Stelgidopteryx serripennis 

Regulus calendula 

Selasphorus rufus 

Grus canadensis 

Passerculus sandwichensis 

Aegolius acadicus 

Sayornis saya 

Ara macao 

lcterus parisorum 

Aphelocoma coerulescens 

Accipiter striatus 

Vireo solitarius 

Melospiza melodia 

o U . S . GOVERWT PR1NTI:iC OFFICE : 

1997- 575- 285165048 

152 

Common name Scientific name 

Spotted towhee 

Steller's jay 

Sulphur-bellied flycatcher 

Summer tanager 

Swainson's thrush 

Thick-billed parrot 

Three-toed woodpecker 

Townsend's solitaire 

Townsenb's warbler 

Tree swallow 

Turkey vulture 

Vaux's swift 

Veery 

Vesper sparrow 

Voilet-crowned hummingbird 

Violet-green swallow 

Virginia's warbler 

Warbling vireo 

Water pipit 

Western bluebird 

Western kingbird 

Western meadowlark 

Western screech owl 

Western tanager 

Western wood pewee 

Whip-poor-will 

White-breasted nuthatch 

White-crowned sparrow 

White-throated swift 

White-winged crossbill 

Whooping crane 

Wild turkey 

Williamson's sapsucker 

Willow flycatcher 

Wilson's warbler 

Winter wren 

Wright's flycatcher 

Yellow-bellied sapsucker 

Yellow-eyed junco 

Yellow-rumped warbler 

Pipilo maculatus 

Cyanocitta stelleri 

Myiodynastes luteiventris 

Piranga rubra 

Catharus ustulatus 

Rhynchopsitta pachyrhyncha 

Picoides tridactylus 

Myadestes townsendi 

Dendroica townsendi 

Tachycineta bicolor 

Cathartes aura 

Chaetura vauxi 

Catharus fuscescens 

Pooecetes gramineus 

Amazilia violiceps 

Tachycineta thalassina 

Vermivora virginiae 

Vireo gilvus 

Anthus spinoletta 

Sialia mexicana 

Tyrannus verticalis 

Sturnella neglecta 

Otus kennicotti 

Piranga ludoviciana 

Contopus sordidulus 

Caprimulgus vociferus 

Sitta carolinensis 

Zonotrichia leucophrys 

Aeronautes saxatalis 

Loxia leucoptera 

Grus americana 

Meleagris gallopavo 

Sphyrapicus thyroideus 

Empidonax traillii 

Wilsonia pusilla 

Troglodytes troglodytes 

Empidonax wrightii 

Sphyrapicus varius 

Junco phaeonotus 

Dendroica coronata 

USDA Forest Service Gen. Tech. Rep. RM-GTR-XXX. 1997. 
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Printed on recycled paper 
Rocky 

Mountains 

Southwest 

Great 

Plains 

U.S. Department of Agriculture 

Forest Service 

Rocky Mountain Forest and 

Range Experiment Station 

The Rocky Mountain Station is one of seven 

regional experiment stations, plus the Forest 

Products Laboratory and the Washington Office 

Staff, that make up the Forest Service research 

organization. 

RESEARCH FOCUS 

Research programs at the Rocky Mountain 

Station are coordinated with area universities and 

with other institutions. Many studies are 

conducted on a cooperative basis to accelerate 

solutions to problems involving range, water, 

wildlife and fish habitat, human and community 

development, timber, recreation, protection, and 

multiresource evaluation. 

RESEARCH LOCATIONS 

Research Work Units of the Rocky Mountain 

Station are operated in cooperation with 

universities in the following cities: 

Albuquerque, New Mexico 

Flagstaff, Arizona 

Fort Collins, Colorado' 

Laramie, Wyoming 

Lincoln, Nebraska 

Rapid City, South Dakota 

'Station Headquarters: 240 W. Prospect Rd., Fort Collins, CO 80526