i

Janet M. Ruth

Research Ecologist

U.S. Geological Survey

Midcontinent Ecological Sicience Center

4512 Mc Murry Avenue

Fort Collins, CO 80525-3400

970-226-9487

FAX 970-226-9230

janet_ruth@usgs.gov

For additional copies or further information, contact:

Nongame Migratory Bird Coordinator, Region 6

U.S. Fish & Wildlife Service

P.O. Box 25486

Denver Federal Center

Denver, CO 80225

March 2000

Cassin’s Sparrow

(Aimophila cassinii)

Status Assessment

and Conservation Plan

Biological Technical Publication

BTP-R6002-2000
ii U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

Recommended citation:

Ruth, J.M. 2000. Cassin’s Sparrow (Aimophila cassinii) status assessment

and conservation plan. Biological Technical Publication BTP-R6002-1999.

U.S. Department of the Interior, Fish and Wildlife Service, Denver, CO.
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 iii

Table of Contents

TABLE OF CONTENTS TABLE OF CONTENTS ............................................................ iii

LIST OF TABLES AND FIGURES ............................................ vii

EXECUTIVE SUMMARY .......................................................... 1

ACKNOWLEDGMENTS ............................................................ 2

TAXONOMY ............................................................................. 3

LEGAL STATUS........................................................................ 3

United States ................................................................... 3

Mexico ........................................................................... 4

DESCRIPTION .......................................................................... 4

Plumage .......................................................................... 4

Adult ........................................................................ 4

Juvenile ................................................................... 5

NATURAL HISTORY ................................................................ 5

Song ............................................................................... 5

Diet ................................................................................ 6

Territory and Site Fidelity................................................... 6

Breeding Ecology ............................................................. 8

Migratory Behavior......................................................... 10

RANGE .................................................................................... 10

Breeding ....................................................................... 11

Migration....................................................................... 12

WIntering ...................................................................... 13

Distribution Changes in Response to Precipitation ............... 14

Theory Regarding Unusual “Migration”

Patterns in Cassin’s Sparrows............................... 17

MONITORING ACTIVITIES ............................................... 18

Breeding Bird Survey (BBS) ....................................... 18

Christmas Bird Count (CBC) ...................................... 19

Breeding Bird Atlases................................................. 19

POPULATION ESTIMATES AND TRENDS ..................... 19

Population Estimates .................................................. 19

Trends ......................................................................... 19

Possible Explanation of Trends ................................... 22

HABITAT............................................................................... 24

Breeding season habitat requirements ........................ 25

Winter habitat requirements....................................... 27

MANAGEMENT ................................................................... 28

Grazing........................................................................ 28

Burning ....................................................................... 31

Conservation Reserve Program (CRP) ....................... 33

Tamarisk ..................................................................... 33

THREATS.............................................................................. 34

Habitat........................................................................ 34

Overutilization for Commercial, Recreational,

Scientific, or Educational Purposes ....................... 34

Disease or Predation ................................................... 34

Inadequacy of Existing Regulatory Mechanisms......... 35

Other natural or ManmadeFactors.............................. 35

Pesticides .............................................................. 35

Population size ..................................................... 35

Nest Parasitism.................................................... 35
iv U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

Table of Contents

Suburban Development........................................... 35

Exotic Grasses........................................................ 36

Grazing .................................................................. 37

Brush Control......................................................... 37

Tamarisk ................................................................ 38

ASSESSMENT AND RECOMMENDATION ............................ 38

Recommendation on current status ................................... 38

CONSERVATION.................................................................... 39

Research Priorities ......................................................... 40

LITERATURE CITED .............................................................. 42

APPENDIX A

STATE SUMMARIES ........................................................... 51

Natural Heritage Program State Ranks Defined ........ 51

UNITED STATES .................................................................. 52

ARIZONA .............................................................................. 52

Summary..................................................................... 52

BBS ............................................................................. 52

CBC ............................................................................ 52

Atlas............................................................................ 52

Research / Monitoring ................................................. 53

Major Populations ....................................................... 55

State Status................................................................. 55

Natural Heritage Rank ............................................... 55

Habitat Condition........................................................ 55

Threats........................................................................ 55

Literature Cited.............................................................. 55

NEW MEXICO......................................................................... 58

Summary........................................................................ 58

BBS ............................................................................. 59

CBC ............................................................................. 60

Atlas............................................................................. 60

Research / Monitoring..................................................... 60

Major Populations........................................................... 62

State Status ................................................................... 62

Natural Heritage Rank .................................................... 62

Habitat Condition............................................................ 62

Threats ......................................................................... 63

Literature Cited.............................................................. 63

TEXAS 65

Summary....................................................................... 65

BBS ............................................................................. 65

CBC ............................................................................. 66

Atlas............................................................................. 67

Research / Monitoring..................................................... 67

Major Populations........................................................... 67

State Status ................................................................... 68

Natural Heritage Rank .................................................... 68

Habitat Condition............................................................ 68

Threats ......................................................................... 68

Literature Cited.............................................................. 69
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 v

Table of Contents

OKLAHOMA ........................................................................... 72

Summary....................................................................... 72

BBS ............................................................................. 73

CBC ............................................................................. 73

Atlas............................................................................. 73

Research / Monitoring..................................................... 73

Major Populations........................................................... 73

State Status ................................................................... 73

Natural Heritage Rank .................................................... 73

Habitat Condition............................................................ 73

Threats ......................................................................... 73

Literature Cited.............................................................. 74

COLORADO............................................................................ 75

Summary....................................................................... 75

BBS ............................................................................. 75

CBC ............................................................................. 76

Atlas............................................................................. 76

Research / Monitoring..................................................... 76

Major Populations........................................................... 77

State Status ................................................................... 77

Natural Heritage Rank .................................................... 78

Habitat Condition............................................................ 78

Threats ......................................................................... 78

Literature Cited.............................................................. 78

KANSAS ................................................................................. 80

Summary....................................................................... 80

BBS ............................................................................. 80

CBC ............................................................................. 80

Atlas............................................................................. 80

Research / Monitoring..................................................... 80

Major Populations........................................................... 81

State Status ................................................................... 81

Natural Heritage Rank .................................................... 81

Habitat Condition............................................................ 81

Threats ......................................................................... 82

Literature Cited.............................................................. 82

WYOMING.............................................................................. 83

Summary....................................................................... 83

BBS ............................................................................. 83

CBC ............................................................................. 83

Atlas............................................................................. 83

Research / Monitoring..................................................... 83

Major Populations........................................................... 83

State Status ................................................................... 83

Natural Heritage Rank .................................................... 83

Habitat Condition............................................................ 83

Threats ......................................................................... 83

Literature Cited.............................................................. 84
vi U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

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NEBRASKA ............................................................................ 85

Summary....................................................................... 85

BBS ............................................................................. 85

CBC ............................................................................. 85

Atlas............................................................................. 85

Research / Monitoring..................................................... 85

Major Populations........................................................... 85

State Status .................................................................... 85

Natural Heritage Rank .................................................... 85

Habitat Condition............................................................ 85

Threats ......................................................................... 85

Literature Cited.............................................................. 86

MEXICO .................................................................................. 87

Summary....................................................................... 87

BBS ............................................................................. 87

CBC ............................................................................. 87

Atlas............................................................................. 87

Research / Monitoring..................................................... 88

Major Populations........................................................... 90

State Status ................................................................... 90

Natural Heritage Rank .................................................... 90

Habitat Condition............................................................ 90

Threats ......................................................................... 91

Literature Cited.............................................................. 91

APPENDIX B

HABITAT DESCRIPTIONS ................................................. 93

Table B1 ...................................................................... 93

Table B2 ...................................................................... 98

APPENDIX C

LIST OF PRIMARY INDIVIDUALS CONTACTED ........ 101
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 vii

Table of Contents

LIST OF TABLES AND FIGURES

Tables Table 1. Linear measurements (mm) of Cassin’s Sparrow ................ 4

Table 2. Information about nest dimensions,

nest placement, and clutch size ............................................ 9

Table 3. Trends for Cassin’s Sparrow from

Breeding Bird Survey data ................................................ 20

Table 4. Average characteristics of plots

occupied by Cassin’s Sparrows .......................................... 25

Table 5. Densities of singing males per square km

in two habitat types........................................................... 26

Table 6a. Results of three related studies

comparing Cassin’s Sparrow responses

to grazing in southeastern Arizona .................................... 30

Table 6b. Results of two related studies

describing effects of grazing on vegetative

cover in southeastern Arizona ........................................... 30

Table 7. Total numbers of birds recorded cumulatively

on plots in burned and unburned native and

exotic grassland in southeastern Arizona .......................... 32

Table 8.. Sample size and means for vegetation

associated with wintering grassland bird species

on the Mexican Plateau of Chihuahua, Mexico. ........................ 88

Table 9. Sample size and means for vegetation variables and

habitat associations of wintering grassland bird

species on the Mexican Plateau of Chihuahua, Mexico. ............. 89

Table 10. Average percentage of basal cover and

shrub density in plots where breeding

Cassin’s Sparrows were present and absent ............................ 90

Figures Fig. 1. Breeding and wintering distribution

of Cassin’s Sparrow ............................................................. 10

Fig. 2. Summer distribution map for Cassin’s Sparrow

from Breeding Bird Survey................................................. 12

Fig. 3. Winter distribution map for

Cassin’s Sparrow from Christmas Bird Count ..................... 12

Fig. 4a. Annual indices of abundance by state for

Cassin’s Sparrow from Breeding Bird Survey..................... 15

Fig. 4b. Annual indices of abundance by physiographic strata

for Cassin’s Sparrow from Breeding Bird Survey................ 16

Fig. 5. Annual population trend estimates for

Cassin’s Sparrow from Breeding Bird Survey..................... 21

Fig. 6. Map of Texas showing Edwards Plateau and

South Texas Brushlands ...................................................... 23

Fig. 7. Cassin’s Sparrow distribution in Arizona .................................... 53

Fig. 8. Historical records of Cassin’s Sparrows in New Mexico ............. 59

Fig. 9. Cassin’s Sparrow distribution in Texas ...................................... 66

Fig. 10. Cassin’s Sparrow distribution in Oklahoma ................................. 74

Fig. 11. Cassin’s Sparrow distribution in Colorado .................................. 77

Fig. 12. Cassin’s Sparrow distribution in Kansas .................................... 81
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 1

EXECUTIVE Cassin’s Sparrow (Aimophila cassinii) is a grassland species endemic

SUMMARY to the southwestern U.S. and northern Mexico. Its behavior and ecology have

been shaped by these arid ecosystems and the health

of its populations is dependent on the availability of grasslands that

contain a shrub component. Populations of many grassland birds have

experienced dramatic declines due to the loss and deterioration of

grassland habitats, and there has been concern about the trends in

Cassin’s Sparrow populations. Without better information about

population trends, ecology, and effects of management activities, and

without a stronger emphasis on grassland management, Cassin’s

Sparrows and other grassland species may continue to experience

declines.

Little information exists about historic Cassin’s Sparrow population

levels, and current population estimates for states in the breeding

range are unknown. Significant survey-wide declines are documented

by the Breeding Bird Survey (BBS) between 1966 and 1996. However,

closer examination of these data suggest that the survey-wide trends

are driven by population declines in the Edwards Plateau and South

Texas Brushlands in Texas. No other areas within the core of its range

or on the periphery show consistent, significant trends. In fact, there is

consensus that in the core of its range in New Mexico Cassin’s Sparrow

remains the most abundant breeding bird in grasslands with a shrub

component. Understanding of population patterns in this species is

complicated by large yearly fluctuations in distribution and numbers at

any particular location, apparently in response to precipitation. This is

particularly obvious in the periphery of its range. These dramatic

fluctuations have hampered a clear assessment of population status,

and our understanding has been confounded by the fact that the timing

of BBS data collection does not always coincide with the peak breeding

season of this species. The lack of information about the Cassin’s

Sparrow’s status, ecology, and response to management activities, and

the apparent declines indicated by BBS data, have been cause for

concern.

Habitat disturbance and degradation, mainly due to grazing and

rangeland management practices such as shrub control, fire

management, and planting of exotics, pose threats to Cassin’s Sparrow

populations, as does habitat conversion through suburban development

and agriculture. There is evidence that heavy grazing negatively

affects populations, but the information is primarily available from the

southwestern portion of its range (Arizona) and may not be applicable

throughout the Cassin’s Sparrow’s entire range. Any management

practice that results in complete removal of the shrub component, or

loss of grass cover and an increase in shrub density beyond a threshold

preferred by the species, also poses a threat. Lack of standardized or

coordinated studies of Cassin’s Sparrow ecology and response to

management practices in different geographic portions of its range has

made it difficult to assess its status and make specific management

recommendations. Limited data are available from the wintering

grounds, and from its range (both breeding and wintering) in Mexico.
2 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

Executive Summary

The greatest needs are for determining of the causes of significant declines

where they occur, determining of the effects of various management activities

on Cassin’s Sparrow throughout its range, improved assessments of population

and trends, and a better understanding of the annual population and distribution

dynamics of this species, which shows such dramatic annual distributional

fluctuations.

ACKNOWLEDGMENTS Special thanks are extended to over 50 people from State agencies, U.S. Fish

and Wildlife Service (USFWS), Bureau of Land Management, U.S. Geological

Survey (USGS), U.S. Army, U.S. Forest Service, universities, and private

organizations in the states throughout the range of the Cassin’s Sparrow who

provided information, without which this report could not have been completed.

I particularly want to acknowledge the review and input provided by: Bruce

Peterjohn, USGS Patuxent Wildlife Research Center; Ray Meyer, La Tierra

Environmental Consulting; Brian Locke, Fort Bliss; Stephanie Jones, USFWS;

Tom Shane; John Dunning, Purdue University; Brent Ortego, Texas Parks and

Wildlife; and Chuck Hunter, USFWS. Front cover illustration by Janet M.

Ruth. Joanne Munro assisted with the range map. Stephanie Jones, USFWS

Region 6 Nongame Bird Coordinator, and Bill Howe, USFWS Region 2

Nongame Bird Coordinator, supported this project and made it possible. Layout

and production provided by Beverly Boecher, USFWS Region 6 Visual

Information Specialist.
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 3

TAXONOMY Common Name: Cassin's Sparrow

Spanish Common Names: Gorrion de Cassin or Zacatonero de Cassin

Scientific Name: Aimophila cassinii

Order: Passeriformes

Family: Emberizidae

The first Cassin's Sparrow was described in 1852 by Samuel W.

Woodhouse from a specimen collected near San Antonio, Texas, and

given its species name in honor of John Cassin, a Philadelphia

ornithologist (Terres 1980). The species was originally known as

Zonotrichia cassinii (AOU 1998). It was subsequently and variously

assigned to the genus Peucaea and eventually to Aimophila around the

turn of the century (Wolf 1977). Much of the confusion seems to have

stemmed from a serious lack of knowledge about the anatomy and life

history of the species included in the genus.

There have been several substantial treatments of the taxonomy of

species within the Aimophila genus (Wolf 1977, Storer 1955) and a

comparison of the song patterns of Aimophila sparrows (Borror 1971),

but they have focused primarily on evaluating the evolutionary

development of these species in order to determine whether this genus

actually consists of an unnatural assemblage of species (actually

representing several taxonomic groups or divergent forms) (Storer

1955). None of these publications called into question the placement of

Cassin's Sparrow within this genus in what is called the "botterii

complex" - Botteri's Sparrow (Aimophila botterii), Bachman's Sparrow

(A. aestivalis), and Cassin's Sparrow (A. cassinii).

No subspecies or races of Cassin's Sparrow are recognized (Pyle 1997;

AOU 1957; Dunning et al. 2000).

LEGAL STATUS

United States Cassin's Sparrow is protected under the Migratory Bird Treaty Act of

1918. The Cassin's Sparrow is not listed as threatened or endangered

under the federal Endangered Species Act. It is included on the list of

"Migratory Nongame Birds of Management Concern in the United

States: the 1995 List" issued by the U.S. Fish and Wildlife Service

(USFWS 1995). In that report, it is listed as a species of concern in

USFWS Regions 2 and 6.

Cassin's Sparrow is listed on the joint National Audubon SocietyPartners in Flight "WatchList" (Muehter 1998), a list of species of

national conservation concern. The WatchList identifies human

alteration of habitat and loss of suitable mixed grass-shrub habitat as

threats.

The Nature Conservancy (TNC) global rank for Cassin's Sparrow is

G5, indicating a demonstrably secure population.

Cassin's Sparrow does not have any legal status in any of the states in

which it occurs. Appendix A provides other details of its status in these

states.

Taxonomy
4 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

Mexico Cassin's Sparrow is protected under the Convention for the Protection of

Migratory Birds and Game Mammals of 1936, but has no other legal status.

DESCRIPTION The Cassin's Sparrow is a fairly large, plain, grayish sparrow that lacks

conspicuous markings. In flight, the long, roundish tail is obvious and

the white tips of the tail feathers are sometimes apparent. This species

is most easily identified by its distinctive song and dramatic skylarking

behavior during the breeding season. Although often characterized in

the literature as secretive and difficult to observe when not singing

(Williams and LeSassier 1968; Oberholser 1974; Kaufman 1990),

Schnase (1984) observed that Cassin's Sparrows readily accommodated

the presence of an observer, especially early in the breeding season.

Average body mass of males in Kansas in June (n = 11) is 17.8 g (range

= 16.9 - 18.5 g) (Rising 1996); average body mass (both sexes) in

southeastern Arizona year round (n = 125) is 18.3 (± 2.9) g (Dunning

and Bowers 1986). Size is 13-15 cm, with males being slightly larger;

the sexes are similar in coloration (Rising 1996). Table 1 shows linear

measurements from collected specimens.

Table 1. Linear measurements (mm) of Cassin's Sparrow. Data shown as mean (range; n).

From Wolf (1977).

Measurement Males Females

Wing Chord 64.0 (62 - 67; 43) 62.0 (59 - 66; 16)

Tail Length 68.0 (64 - 71; 13) 66.0 (62 - 71; 13)

Tarsus 19.9 (18.5 - 21.4; 45) 19.8 (18.8 - 21.4; 37)

Culmen Length

 (from anterior of nostril) 7.7 (6.8 - 8.3) 7.5 (7.0 - 8.2)

Bill Depth 4.9 (4.5 - 5.5) 4.8 (4.5 - 5.1)

Plumage Plumage references (Rising 1996; Byers et al. 1995; Kaufman 1990).

Adult - The head is brown streaked with gray and dark brown; the

supercilium is buff, and there is a thin, dark brown submoustachial

stripe. The bill is brownish gray, with darker upper mandible and pale

bluish gray tomial edge and lower mandible. The iris is dark brown.

The chin, throat and breast are pale gray or brownish gray; the belly is

whitish; and there are a few well-defined dark brown or black streaks

on the lower flanks. On the back, the mantle and scapulars are

described as brown or gray with a rusty tinge, the feathers having dark

brown subterminal spots and edged with buff or gray, giving a scaly or

variegated appearance. Wings are brown; greater coverts are broadly

tipped and narrowly edged with buff or grayish white, forming a wing

bar variously described as fairly conspicuous to indistinct. The alula is

pale yellow. Feathers in the upper tail coverts have a gray edge, a

brown center, and a black subterminal crescent. The undertail coverts

are buffy. Most of the upper side of the tail is dark, dusky brown, but

the central two rectrices are pale brownish gray with a serrated dark

central strip that spreads out into a suggestion of faint crossbars. The

lateral two rectrices are edged and tipped in pale gray or white, with smaller

Legal Status
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 5

pale areas at the tips of the next two pairs inward. This is sometimes noticeable

on a bird flushing or flying away, but it is not always apparent, and by late

summer, pale tips may be partly or completely worn away. Legs are described

as dull pinkish or dark flesh.

Juvenile - Juveniles are similar to adults with a brown back, feathers with buffy

tips and darker brown central streaks, greater coverts edged with white, and

light streaking on breast and throat.

Byers et al. (1995) noted that some birds, mainly in the eastern part of

their range, tend to be more rufous above, slightly buffier below, and

have plainer tails with less obvious shaft streaks and barring on the

central rectrices. Although rarer, even in the eastern part of the range,

the rufous morph has been observed as far away as the Farallon

Islands off California (J. Dunning pers. commun.).

Willoughby (1986) reports on an unusual sequence of molts and

plumages in Cassin's and Bachman's Sparrows – replacement of all

pennaceous body plumage twice within a bird's first six months of age,

and a gradual molt of body feathers in adults throughout the breeding

season. Designated as a presupplemental molt, this molt has been fully

documented in certain species only recently, having been found in 16

species of North American passerines to date (Pyle 1997).

NATURAL HISTORY

Song The Cassin's Sparrow's primary song consists of six note complexes,

beginning with a soft double or single introductory note, followed by a

long, high musical trill on one pitch, and (usually) two lower, wellspaced musical notes, all with a slight minor-key quality. There is

enough individual variation in this song that it has been used as a

means of identifying individual males in population studies (Schnase

and Maxwell 1989). A secondary song, or "chitter" song (Wolf 1977),

consists of a series of chips, trills, and buzzy notes preceding the

primary song (Schnase 1984). Cassin's Sparrows also give a variety of

chitter calls and chip notes that have been assigned various roles by

different authors, including pair bond maintenance, communication

with fledglings, alarm calls, territory defense, etc. (Kaufman 1990;

Schnase 1984; Wolf 1977). Unusual conditions may induce this species

to sing at unusual times of year (Kaufman 1990).

Territorial males sit in low bushes or grass, or on the ground to sing,

but often give spectacular flight-songs. At the beginning of the

breeding season, all song is from a stationary, exposed perch and often

involves reciprocal proclamation of the primary song among males.

Flight songs and skylarking are infrequent until later, in association

with the presence of returning females (Schnase et al. 1991; Schnase

1984). In flight songs (or skylarking), the territorial male flies up from

an exposed perch, such as a bush, to as much as 5 - 10 m in the air, then

sings as he glides or flutters down in an arc to a nearby bush or the

ground. During the descent, wings are held flat, the head is arched

backwards, and the tail is elevated. Song can be heard from mid-February to

early September, depending on location, with considerable night singing at the

Discription
6 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

height of the season reported by some (Rising 1996; Howell and Webb 1995;

Schnase 1984; Oberholser 1974).

Diet The summer diet of Cassin's Sparrows consists primarily of insects,

especially grasshoppers, caterpillars, and beetles. Additional insects

specifically mentioned in the literature include true bugs, ants, bees,

wasps, weevils, spiders, snails, and moths (Dunning et al. 2000;

Kaufman 1996; Bock et al. 1992; Oberholser 1974; Williams and

LeSassier 1968). The young are fed almost entirely insects (Kaufman

1996). Bock et al. (1992) note that observations of a Cassin's Sparrow

nest for 18 hours in 1984 showed that of 208 insects delivered to

nestlings, 197 (95%) were acridid grasshoppers. However, Wolf (1977)

reported that the stomachs of ten adults taken during the breeding

season (late June and early July) contained animal and vegetable

matter in about equal proportions (52% and 48%, respectively; range =

5 - 95%). He also found that five migrant Cassin's Sparrow stomachs

contained 99% animal material (range = 90 - 100%). There is a report of

Cassin's Sparrows eating flower buds of blackthorn bush (Condalia

spathulata) in season (Oberholser 1974). In fall and winter, Cassin's

Sparrows eat the seeds of weeds and grasses (Kaufman 1996; Williams

and LeSassier 1968). Oberholser (1974) particularly mentions the

consumption of seeds of chickweed (Alsinaceae family), plantain

(Plantago spp.), woodsorrel (Xanthoxalis spp.), sedge (Carex spp.),

panicum (Panicum spp.), other grasses, and sorghum (Sorghum spp.).

Schnase (1984) reports observing birds drinking water from a small

pool immediately following a rain. Although Williams and LeSassier

(1968) report that Cassin's Sparrows seem to exist very well without

drinking water, their conclusion appears to be based on the limited

number of recorded observations of this species drinking water, the

distance of most nesting areas from water, and the fact that birds rarely

leave their territories.

Cassin's Sparrows forage mostly or entirely on the ground, hopping

about in relatively open areas, taking items from the ground or from

plant stems (Kaufman 1996, Schnase 1984). When flushed, they fly to a

bush or fence, or may drop back into the grass (Rising 1996). Schnase

(1984) reported that foraging occurred in a slow, methodical manner.

Foliage gleaning from within mesquite (Prosopis spp.) and other

shrubs was only prominent after nestlings and fledglings were present.

Fledglings apparently acquired most of their food in this manner rather

than on the ground.

Territory and Cassin's Sparrows establish and maintain breeding territories solely

Site Fidelity by song (Schnase et al. 1991); mating, nesting, and feeding occur within

these territories. Mean territory size over two years (n = 21) in southcentral Texas was found to be 2.6 (± 0.5) ha (Schnase 1984); the

information was also presented as a mean density of 11 birds per 40.4

ha. A number of other studies have reported Cassin's Sparrow

breeding densities. However, it is unlikely that these numbers can be

compared with each other since various methods of data-gathering and

analysis were used. Nevertheless, they do provide some idea of the

Natural History
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 7

possible densities for this species. Another study in south-central

Texas found densities ranging from 33 birds per 40.4 ha in scrubby

mesquite grassland to six birds per 40.4 ha in bottomland mesquite

woodland (Maxwell 1979). A Breeding Bird Census on a 61 ha plot on

the Buenos Aires National Wildlife Refuge in Arizona found 15 Cassin's

Sparrow territories for a density of ten territories per 40 ha (Gordon

and Leitner 1996). By comparison, A. Flesch (written commun.)

reports that in a good year, Buenos Aires NWR supported densities

of 86 singing males per 40 ha. In an unpublished study of bird

communities in sacaton (Sporobolus sp.)-mesquite grasslands along the

San Pedro River in Arizona, one transect showed annual peak breeding

densities (based on Emlen transects) of 41, 66, 91, and 19 birds/40 ha in

respective years; a second transect showed annual peak densities of 39,

26, and 14 birds/40 ha (D. Krueper written commun.). A study of avian

communities within a variety of habitats along the Pecos River

(Hildebrandt and Ohmart 1982) found a range of Cassin's Sparrow

densities (presenting calculations from the summer periods of June -

July and August - September). They found 6 - 12 birds per 40 ha in

sparse (little foliage volume above 1.5 m) honey mesquite (Prosopis

glandulosa) habitat; 6 - 12 birds per 40 ha in sparse four-winged

saltbush (Atriplex canescens) habitat; 6 - 24 birds per 40 ha in low (little

foliage above 3 m) to sparse tamarisk (Tamarix chinensis) habitat; 2 - 7

birds per 40 ha in cleared communities dominated by annual and

perennial weeds and shrubs; and 3 - 4 birds per 40 ha in cleared

communities dominated by grass.

Schnase (1984) found no overlap in territorial boundaries, and adjacent

territories were separated by 15-75 m; Johnsgard (1979) reported that

territorial males may be spaced 50-100 yards apart. Both Williams and

LeSassier (1968) and Johnsgard (1979) report observations of clusters

or groups of breeding Cassin's Sparrows and suggested that they may

be semi-colonial.

Research on site fidelity in wintering grassland birds in southeastern

Arizona (Gordon In Press a and b) found high within-season recapture

rates for Cassin's Sparrows on seven ha plots, indicating very

sedentary behavior for this species. Using three years of data, he

calculated the recapture event rate - rer (the number of recaptures

divided by the number of opportunities for recapture). Cassin's

Sparrow (rer = 0.11) and Grasshopper Sparrow (Ammodramus

savannarum) (rer = 0.09) remained within a very small area (or

territory) during the winter, showing significantly higher (P < 0.05)

recapture rates than Baird's Sparrow (A. bairdii) (rer = 0.04),

Savannah Sparrow (Passerculus sandwichensis) (rer = 0.01), Vesper

Sparrow (Pooecetes gramineus) (rer = 0.02), and Brewer's Sparrow

(Spizella breweri) (rer = 0.004). Patterns of between-year capture and

recapture rates in wintering Cassin's Sparrows indicate great

variability, possibly tied to between-year nomadism, between-year

population fluctuation, or expansion-retraction along the edge of their

range (C. Gordon written commun.). For example, at the same plots

with the same level of effort, nine Cassin's Sparrows were captured in the

winter (January to March) of 1997 and 43 were captured in 1998. One of the

Natural History
8 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

nine individuals from 1997 was recaptured in 1998, and in 1999, one "1997 bird"

(a different one), and one "1998 bird" were recaptured (all of these recaptures

on the same seven ha plots on which they were first banded), indicating that

between-year site fidelity does exist to some extent.

Breeding Ecology Breeding in Cassin's Sparrow across its range can occur from March

through September. Rising (1996) notes that breeding appears to take

place in early summer in coastal Texas, Kansas, Colorado, and northeast New Mexico, and in late summer (after the rains) in southeastern

Arizona. See Appendix A for specific information about breeding

timing and records from individual states.

Schnase (1984) reports indirect evidence that Cassin's Sparrows form

stable, monogamous pair bonds. Some sources believe that this species

may double-brood (Baicich and Harrison 1997; Rising 1996; Wolf 1977).

However, Schnase (1984) reported that, although renesting took place

in three cases where abandonment or destruction of a clutch occurred

before mid-June, there was no evidence that any of the 25 pairs he

observed successfully reared more than one clutch.

Schnase (1984) reports that females returned later than males in the

spring and their return coincided with the onset of skylarking by males.

Males pursued females to the border of their territories. Males

frequently pursued females in slow, horizontal flight no more than 2-3

m above the ground while producing the "chitter" call. Copulation has

only been observed rarely. Schnase (1984) reports that the male

initiates a courtship display involving an erect head and tail with wings

fluttering in an outstretched position which is followed by copulation;

this was seen twice on the ground and once in a low mesquite.

Cassin's Sparrows nest on or near the ground. There are

approximately equal numbers of reports of ground nests and nests

elevated a few inches off the ground in shrubs or other vegetation

approximating shrub structure (e.g., cactus). Nests on the ground are

usually concealed in tall grass or grass tufts, or at the base of shrubs or

Opuntia cacti (Baicich and Harrison 1997; Rising 1996; Schnase 1984,

Johnsgard 1979; Williams and LeSassier 1968). Nests in shrubs are

rarely located more than 12 inches above the ground (Table 2). They

are often found in the midst of a tangled patch of Opuntia cactus

(Williams and LeSassier 1968). The nest is a deep cup constructed of

dead grasses, weed stems, bark and plant fibers, and sometimes grass

flowers. It is lined with finer grasses and grass flowers, rootlets, and

sometimes hair (Baicich and Harrison 1997; Rising 1996; Williams and

LeSassier 1968).

Natural History
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 9

Table 2. Information about nest dimensions, nest placement, and clutch size from studies in

southeastern Arizona (Maurer et al.1989), Texas (Schnase 1984; Schnase et al. 1991)

and New Mexico (A. Pidgeon written commun.).

Maurer et al. 1989 Schnase 1984; Pidgeon written

Schnase et al. 1991 commun.

Avg. nest height

 from ground (cm) 10.8 (±5.9) (n = 18) 4.0 (±2.3) (n = 10) 15.0 (n = 6)

Avg. cup depth (cm) 5.4 (± 0.4) (n = 17) 6.4 (± 1.0) (n = 10) N/A

Avg. cup width (cm) 6.5 (± 0.4) (n = 18) 5.9 (± 0.6) (n = 10) N/A

Nest plant height (m) 0.7 (± 0.2) (n = 18) 0.4 (±0.1) (n = 9) 0.6 (n = 6)

Avg. clutch size 3.0 (±0.9) (n = 10) 2.2 (±?.?) (n = ??) 3.7 (n = 10)

The subelliptical eggs of Cassin's Sparrows are white and unmarked,

smooth and slightly glossy. The average size is 19 x15 mm. Cassin's

Sparrows lay three to five eggs, usually four (Table 2) (Baicich and

Harrison 1997; Johnsgard 1979; Williams and LeSassier 1968).

Berthelesen and Smith (1995) found a slightly larger average clutch size

in their study (4.4 ± 0.61, n = 34).

Little documented evidence was found on the incubation period for

Cassin's Sparrow. Baicich and Harrison (1997) estimate it at ten days.

Schnase et al. (1991) observed incubation of 11 days in one nest. They

found that females laid one egg each morning and began incubation

with the third egg of a four-egg clutch. Males were never observed at

the nest, and Schnase et al. (1991) assumed that females were the

primary brooders. Dunning et al. 2000 Data for three Arizona nests in

which the incubation period was 11 days, 11 days, and 9 days for the

three nests (Dunning et al. 2000).

Nestlings are altricial, with sparse, very dark down (Baicich and

Harrison 1997); Schnase (1984) described nestlings as naked except for

sparse, light-gray down on the head and back, with pronounced yellow

rictal flanges and dark red mouth lining. Most records indicate that the

nestlings are tended by both parents (Baicich and Harrison 1997;

Williams and LeSassier 1968; Johnson 1956), but Schnase et al. (1991)

found little evidence regarding male-female cooperation in feeding

nestlings. The parents are extremely secretive in their approach to the

nest, making nest finding very difficult. A. Flesch (written commun.)

reported observing parents carrying fecal sacs. Nestlings leave the

nest at approximately nine days (Baicich and Harrison 1997, Schnase et

al. 1991). Schnase et al. (1991) did find that females assumed primary

responsibility for care of the young once they fledged. In addition, they

found that within two days of fledging, young were capable of repeated

flights of 10-15 m, and that periods of independent foraging in

vegetation and on the ground were common for fledglings eight days

after leaving the nest.

Eventually fledglings became less dependent and associated with

fledglings from adjacent territories in flocks of as many as 10-20

individuals that moved throughout territories (Schnase 1984).

Natural History
10 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

Very little information is available regarding productivity in Cassin's Sparrows

and the minimal information available from different studies is widely variable.

Schnase (1984) observed a total of 40 fledglings produced by 25 males for a 1.6

fledglings/male ratio over three summers. Two of the 25 males were unpaired,

and five of 23 pairs were not successful in fledging any young. Schnase

identified productivity by male because individual birds in the study (males)

were identified primarily by variation in song. The presentation of these data

made further interpretation difficult. A study of breeding bird use of

Conservation Reserve Program (CRP) lands in the Texas Panhandle

(Berthelsen and Smith 1995) estimated Cassin's Sparrow nest success

(n = 34) as 44 (± 0.89) % through fledging, using the Mayfield method.

Preliminary data from a study on Fort Bliss (n = 10) found the mean

number fledged per nest was 1.9 (A. Pidgeon written commun.).

Migratory Behavior Nothing is known about the migratory behavior of this species.

RANGE Cassin's Sparrow is a species of the southwestern U.S. and central Mexico

(Figure 1).

Figure 1. Breeding and wintering distribution of Cassin’s Sparrow. They are found in suitable

grassland/shrubland habitat within the boundaries shown.

Natural History
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 11

There is little information about the historical range of Cassin's Sparrow, and

therefore little evidence of whether the species' range has expanded or

contracted. This is complicated by the annual fluctuations in distribution of this

species. However, records in the last twenty years of Cassin's Sparrows

breeding in Wyoming and Nebraska may represent an expansion of their

distribution, in some years at least. Hubbard (1977) suggests that the more

recent documentation of breeding Cassin's in southwestern New Mexico and

southeastern Arizona may also represent an expansion of their breeding range.

Breeding Even the current breeding range for this cryptic species continues to

be difficult to define. Cassin's Sparrows are sometimes very common

but are irregular, with large numbers often appearing in an area after

good rains have caused vegetation to turn green (Kaufman 1996). In

addition, because there have been so few records of Cassin's Sparrow

nests, many of the descriptions of breeding range are based on the

presence of singing males.

The breeding distribution of the Cassin's Sparrow is described by

Breeding Bird Survey (BBS) data (Figure 2).

Figure 2. Summer distribution map for Cassin’s Sparrow from Breeding Bird Survey (BB) 1982-1996

(Sauer et al. 1997). This is the average relative abundance of the species detected per BBS

route per year.

BBS SUMMER DISTRIBUTION MAP 1982-1996

Range
12 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

Figure 3. Winter distribution map for Cassin’s Sparrow from Christmas Bird Count (CBC) 1966 - 1989

(Sauer et al. 1996). This is average relative abundance of the species per CBC circle.

CBC WINTER DISTRIBUTION 1966 - 1989

A compilation of existing descriptions of the species' breeding

distribution from the literature yields the following (Howell and Webb

1995; Rising 1996; AOU 1998): Cassin's Sparrows breed from

southwestern Nebraska, western Kansas, southeastern Colorado

(irregularly into northeastern Colorado), southern and eastern New

Mexico, western Oklahoma, western two-thirds of Texas, Chihuahua,

Coahuila, in the interior south to Zacatecas and San Luis Potosí, and on

the Atlantic slope from Nuevo Leon to Tamaulipas. Sporadic records

exist for central and eastern Wyoming, and southwestern South

Dakota. See Appendix A for detailed information on distribution within

individual states.

Migration Cassin's Sparrows are migratory in the northern part of their range,

withdrawing basically into the southern part of their range and

possibly a little farther south in Mexico for the winter. Defining the

arrival and departure times for Cassin's Sparrows throughout their

range is somewhat difficult because the data are derived from

miscellaneous arrival, breeding, and nesting dates. A migratory flux of Cassin's

Sparrows arrives in Texas in March, even in areas where some individuals

overwinter (Hubbard 1977), and Texas has the earliest breeding records for

Cassin's Sparrow - early March (Hubbard 1977; Oberholser 1974). They are

Range
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 13

reported breeding in Mexico in April (Howell and Webb 1995). They also

return to New Mexico in large numbers in early April (Hubbard 1977) and to

Oklahoma by late April (Baumgartner and Baumgartner 1992). The first nestbuilding in southeastern Colorado was observed in mid-May (J. Bradley pers.

commun.), but the Colorado Breeding Bird Atlas records most nesting activity

beginning in early June (Kingery 1998). Egg dates for Kansas begin in midMay (Johnsgard 1979). Breeding of Cassin's Sparrows begins in southeastern

Arizona in July (Maurer et al. 1989; Monson and Phillips 1981).

It appears that Cassin's Sparrows may leave Colorado and Oklahoma

by the end of August. The last nest monitored for fledglings in

southeastern Colorado during a 1996 study was in the first week of

August (J. Bradley pers. commun.), and Cassin's Sparrows are

recorded through August in Oklahoma (Baumgartner and

Baumgartner 1992). The majority leave New Mexico by late

September (Hubbard 1977). In Texas, breeding records occur through

early August and the winter season for Cassin's Sparrows begins in

mid-October (Oberholser 1974). Breeding in southeastern Arizona and

Mexico continues through September (Maurer et al. 1989; Monson and

Phillips 1981; Howell and Webb 1995). Migration patterns in Arizona

continue to be poorly defined, and although Cassin's Sparrows winter

over most of their breeding range in Mexico, there may be some

withdrawal south during that period (Howell and Webb 1995).

Cassin's Sparrows sometimes turn up far outside their normal range

during migration, with scattered records from coast to coast (Kaufman

1996). Roberson (1980) reports five records of spring and fall vagrants

in the Southeast Farallon Islands, California, as well as spring and

summer nomads in potential breeding habitat in southern California

(25 records), where singing males defended territories for a brief time

and then disappeared. They have been reported as casual or accidental

in Nevada, Ontario, Nova Scotia, Missouri, Illinois, Indiana, and New

Jersey (Rising 1996; AOU Checklist 1998; Dunning et al. 2000). Russell

and Monson (1998) also documented unexpected locations for Cassin's

Sparrows outside their normal range in Mexico in years of abovenormal rainfall (e.g., a dozen singing Cassin's Sparrows among sand

dunes near Puerto Peñasco (far northwestern Sonora) in late Marchearly April 1984.

There are reports of gender differences in migration patterns, with

males appearing in Texas in the spring at least two weeks before the

females (Schnase et al. 1991; Schnase 1984).

Wintering The winter distribution of Cassin's Sparrows in the U.S. is based on

Christmas Bird Counts (Figure 3).

Unfortunately, similar information does not exist for its primary winter

range in Mexico. A compilation of the descriptions in the literature of

the species' wintering range results in the following (Howell and Webb 1995;

Rising 1996; AOU 1998): Cassin's Sparrows winter in southeastern Arizona,

only rarely or sporadically in southern New Mexico, in western and southcentral Texas, and into Mexico on the Pacific slope from Sonora through

Range
14 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

Sinaloa to Nayarit and south in the interior including Chihuahua, Coahuila,

Zacatecas, San Luis Potosí and Guanajuato. See Appendix A for available

details on winter distribution in individual states.

Distribution Changes There is a consensus, throughout the literature and among the

In Response To contacts made for this report, that breeding Cassin's Sparrows are

Precipitation very responsive to precipitation. However, little is offered in the way

of evidence or specific descriptions of that response. In addition, there

appear to be some differences of opinion regarding how this response

manifests itself. Many references associate variations in Cassin's

Sparrow abundance with variations in precipitation patterns and

associated vegetation growth, but some suggest that there are more

Cassin's Sparrows when there is more rain (Phillips 1944; Williams and

LeSassier 1968), while others suggest that there are more birds when

there is less rain (M. Howery pers. commun.; C. Sexton, written

commun.; Andrews and Righter 1992). These differences may be

related to different geographic locations and associated weather

patterns. Baumgartner and Baumgartner (1992) spoke most clearly

about this. They noted that Cassin's Sparrows are most abundant in

western Oklahoma, but that they expand eastward in the state during

periods of drought, when vegetation is stunted and pastures that

normally sustain tall or mixed grasses approximate the more arid

conditions of western plains.

Maurer (1985) conducted a broad study of avian community responses

to temporal distribution of rainfall and spatial distribution of mesquite

trees on the Santa Rita Experimental Range (SRER). Although the

focus was on community-level responses, he did present information

specific to Cassin's Sparrows. In southeastern Arizona, July through

September is the season of greatest rainfall, with an associated high

grass productivity (Cable 1975) and increase in available insect biomass

(Maurer 1985). During the first year of this study, the site received

average rainfall; during the second year it received abnormally high

winter precipitation and somewhat delayed, but normal, summer

rainfall. The following data were extracted from Maurer (1985), but did

not include statistical tests for significance. In grassland habitats with

low mesquite densities (the habitat preferred by Cassin's Sparrows),

Cassin's Sparrow densities increased in the breeding season following

greater precipitation (1982 - 43.2 males/km2; 1983 - 71.2 males/km2).

Even in mesquite savannah habitat (less preferred by Cassin's

Sparrows), bird densities increased following the year of greater

precipitation (1982 - 4.9 males/km2; 1983 - 34.5 males/km2).

To summarize these observations, it appears that the broad temporal

fluctuations in Cassin's Sparrow distribution and numbers (Figure 4a

and 4b) are a response to changes in timing and amount of precipitation.

Range
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 15

Figure 4a. Annual indices of abundance by state for Cassin’s Sparrow from Breeding Bird Survey.

Annual indices of abundance are estimated as residuals from the route-regression. The

line, depicting the predicted trend in counts over time, is drawn using the regional

trend estimate and a regional average count (Sauer et al. 1997).

Range
16 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

Figure 4 b. Annual indices of abundance by physiographic strata for Cassin’s Sparrow from

Breeding Bird Survey. Annual indices of abundance are estimated as residuals from the

route-regression. The line, depicting the predicted trend in counts over time, is drawn

using the regional trend estimate and a regional average count (Sauer et al. 1997).

Range
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 17

The most likely factors to which they are ultimately responding are changes in

vegetative structure and vigor. Thus, at the eastern and northern edges of their

range, where there is usually more rainfall and the grass structure is usually too

tall or dense for Cassin's Sparrow habitat, Cassin's Sparrows only expand or

increase in abundance in dry years. In these dry years the vegetative structure

is stunted and sparse, and more closely approximates their preferred habitat. In

contrast, at the southwestern edge of their range, where rainfall can be quite

sporadic and the grass structure in dry years is not sufficient to support Cassin's

Sparrows, Cassin's Sparrows only expand or increase in abundance in wet

years, when the vegetative structure is lush enough for them. In the core of

their range, a similar pattern may be occurring, which is manifest as increases in

abundance in years with precipitation and habitat structure that are optimal, and

decreases in suboptimal years. However, such fluctuations would be more

difficult to observe because they are not accompanied by expansions in

distribution.

There remains much to understand about the factors affecting Cassin's

Sparrows dramatic fluctuations in distribution. Although they appear

to be responding to the effects of changing precipitation patterns, the

actual process by which precipitation affects them is unclear. They may

be responding to changes in vegetative structure or composition

needed for nesting, hiding from predators, or courtship displays, as

suggested above. In that case, the rapid response noted in the birds,

which often seem to appear and begin singing within days of the first

rains of the season and before the vegetation has responded, remains to

be explained. It may mean that they have evolved to respond to the

initiation of rain itself as a proximal cue, rather than the actual

greening of vegetation which follows. An alternative explanation for

the Cassin's Sparrow response to precipitation is that they are

responding to changes in prey populations (particularly insects such as

grasshoppers) that in turn are responding to changes in precipitation.

There is no direct evidence of this association, but Maurer (1985)

concluded that the influence of rainfall on insect productivity strongly

affected the avian community in Arizona, and there is evidence that

grasshopper populations respond positively to precipitation in the

southwestern U.S. (Capinera and Horton 1989; Capinera and

Thompson 1987; Nerney 1961).

Theory Regarding There remains an unresolved controversy regarding the migration

Unusual “Migration” and breeding patterns of Cassin’s Sparrows. Phillips (1944) was the

Patterns In first to specifically address this issue. He based his hypothesis on

Cassin’s Sparrows the lack of documentation of breeding in Arizona at the time, and his

observations that large numbers of Cassin's Sparrows did not appear in

the state until July and August, when males sang and were in breeding

condition (enlarged testes). Phillips concluded that the species did not

breed in Arizona but rather migrated east-to-west, from its principal

breeding areas in Texas to southeastern Arizona, where it was an

abundant fall transient and an irregular, rather common winter

resident.

Range
18 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

Subsequently, nesting Cassin's Sparrows have been documented in southeastern

Arizona in late summer (Monson and Phillips 1981; Ohmart 1966). In response

to this evidence, Ohmart (1969) suggested that a single population of Cassin's

Sparrows took advantage of the food source provided by spring rains on the

Great Plains, and then moved southwest for a second breeding season in the

Sonoran Desert in response to food sources produced there by late summer

rains. Wolf (1977) suggested that the late summer males might be individuals

that did not mate during the breeding season (presumably on the southern Great

Plains) and were migrating early without undergoing gonadal regression.

Hubbard (1977) espoused the view that Cassin's Sparrows may have bred very

locally and perhaps irregularly in Arizona for some time, but that the bulk of the

late summer birds were nonbreeders.

Although there are no published studies addressing this issue, there

are very strong opinions about the hypothesis. There are those who

believe that Cassin's Sparrows are also present in southeastern

Arizona during spring and early summer but are so cryptic and

secretive that they are simply not observable until they begin singing

and skylarking in response to late summer rains. Others are very

insistent that if Cassin's Sparrows were present, even if acting

secretive, experienced birders and researchers would have detected

them. Still others are more comfortable with an intermediate

interpretation – that Cassin's Sparrows are simply very opportunistic

and move around on a much larger scale than most species, looking for

the right combination of rain, vegetation, and food resources needed for

breeding. In any case, this is an unresolved question regarding

Cassin's Sparrow ecology.

MONITORING ACTIVITIES

Breeding Bird Survey Monitoring of breeding Cassin's Sparrows on a range-wide basis in

(BBS) the United States, and to a minimal extent in Mexico, is restricted to

the BBS. The interpretation of BBS data is limited in at least some

areas by the low numbers and distribution of routes completed in an

area, by the highly variable nature of Cassin's Sparrow annual

distributions, and by the fact that their most active, observable

breeding season at times coincides with the early summer timing of

BBS data collection and at times does not.

A three-year BBS feasibility study was conducted in Mexico from 1993

- 1996. None of those routes have been surveyed subsequently. With

the exception of a few routes that are sporadically surveyed by U.S.

citizens, the BBS does not exist in Mexico at this time. Expansion of the

BBS program, or an equivalent, into Mexico would provide valuable

information about Cassin's Sparrow populations there.

Results of BBS data analysis and additional details about BBS data

from individual states and Mexico are presented elsewhere (Trends

section and Appendix A).

Range
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 19

Christmas Bird Count The Christmas Bird Counts in the southwestern part of the United

(CBC) States only cover a small portion of the Cassin's Sparrow winter range (Root

1988). There are a few CBCs done in Mexico by coalitions of U.S., Mexican,

and in some cases Canadian citizens, primarily in Sonora, Chihuahua, and

Tamaulipas, although there is no organized program for the country.

Breeding Bird Atlases Breeding Bird Atlases (BBAs) are conducted by states to document the

distribution and reproductive status of breeding birds within their

borders. Most BBAs are five-year projects, however, some states plan

to periodically repeat Atlas projects. Once repeated, atlas projects will

provide valuable information on changes in Cassin's Sparrow

distribution. Although only one state within its range (Colorado) has

published its breeding bird atlas, Cassin's Sparrows were detected

during BBA data collection in six states - Arizona (Arizona Breeding

Bird Atlas unpub. data), Texas (Arnold and Benson unpub. data),

Oklahoma (Oklahoma Breeding Bird Atlas unpub. data), Kansas (Busby

and Zimmerman unpub. data), Colorado (Kingery 1998), and Nebraska

(Sharpe et al. unpub. data). New Mexico and Wyoming have not

conducted Breeding Bird Atlas projects. Summaries of BBA data for

each state can be found in Appendix A.

Although there are no other range-wide monitoring programs, there

are some site-specific monitoring projects being conducted at various

locations (Appendix A).

POPULATION Great fluctuations in annual numbers at any particular location make

ESTIMATES AND TRENDS it difficult to estimate the overall population of Cassin's Sparrows or monitor

trends in that population.

Population Estimates No population estimates for Cassin's Sparrows were found in the

literature or during the compilation of information for this report.

Trends The best available description of population trends for Cassin's

Sparrow is from BBS data analysis. For purposes of this document,

trends with a P-value < 0.20 are presented; any pattern with a larger Pvalue is considered nonsignificant.

Survey-wide data for Cassin's Sparrow during the entire time period

for which BBS data are available (1966 - 1996), show a highly significant

decline (Table 3). During this same time period, Cassin's Sparrow data

in Texas show a similar, highly significant downward trend, with

Colorado and Kansas also showing a significant decline. No other state

data within the bird's range show any significant trends in either

direction for the entire BBS time period (Sauer et al. 1997). Figure 4a

shows annual indices of abundance for New Mexico, Texas, Colorado,

and Oklahoma. Figure 5 maps the variation in population trend

estimates for this species over the entire time period covered by BBS.

Monitoring Activities
20 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

Table 3. Trends (average percent change per year) for Cassin's Sparrow from Breeding Bird

Survey data from 1966-1996 (Sauer et al. 1997; Sauer unpub. data

a

).

P-value: * 0.10 < P < 0.20 ** 0.05 < P < 0.10; *** 0.01 < P < 0.05;   P <0.01(1)

Total Time Period

 1966 - 1996 1966 - 1979 1980-1996

Trend p - value n Trend p - value n Trend p -value n

SURVEY-WIDE -2.5 ** ** 203 +0.4 96 -0.2 186

STATES

Arizona +1.5 5 N/A N/A +2.8 5

Colorado -4.1 * 32 -9.6 ** 8 +2.6 *** 32

Kansas -8.3 * 10 -4.1 6 -1.2 7

New Mexico +0.3 36 +0.5 9 -1.1 35

Oklahoma +3.0 20 +9.3 * 8 +1.2 18

Texas -2.9 **** 99 +1.8 63 -0.9 89

PHYSIOGRAPHIC STRATA(2)

S. TX Brushlands -3.4   21 +5.2 **  16 -2.9 * 19

High Plains Border -0.8 15 +8.6 * 9 -2.5 * 11

High Plains -4.5 * 31 -8.8 *** 10 +2.5 *** 30

Edwards Plateau -7.0 **** 19 -4.8 * 14 -5.7 **** 17

Rolling Red Plains -0.9 19 -1.4 10 +0.6 18

Staked Plains -0.3 27 -0.8 11 -0.6 25

Chihuahuan Desert -1.7 29 +1.6 14 -0.5 28

Intermt. Grasslands -0.4 18 +2.5 3 -2.7 17

REGIONS

Central BBS Region -2.6 **** 149 +0.3 77 0.0 134

Western BBS Region -1.9 * 54 +1.8 19 -1.1 52

USFWS Region 2 -2.3 **** 160 +1.7 81 -0.9 * 147

USFWS Region 6 -4.4 * 43 -8.5 *** 15 +2.5 *** 39

(1) Without a significant p - value, there is no evidence that the trend is significantly different from zero (no

trend), and without sufficient sample size (BBS normally only calculates trends with a sample size of n > 14),

trend estimates are not reliable. A few results with n< 14 are presented here solely to document the limited

data available for some areas within Cassin’s Sparrow range.

(2) Some Physiographic Strata have recorded a few Cassin’s Sparrows, but the sample size is not large enough

to calculate a trend estimate - Coastal Prairies; Oaks and Prairies; Osage Plains; Rolling Red Prairies; and

Mexican Highlands.

When BBS data analysis is broken down into shorter time periods

(Sauer et al. 1997), however, the patterns rapidly break down (Table 3).

Survey-wide data for Cassin's Sparrow show no significant trends for

either the 1966 - 1979 or the 1980 - 1996 periods. At the state level

Colorado data show a significant decline for 1966 - 1979 and a very

significant increase for 1980 - 1996. Oklahoma data show a somewhat

significant increase for 1966 - 1979, and no significant pattern for 1980 -

1966. No other state data show any significant trends for either of these

Population Estimates and Trends

shorter time periods.
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 21

Figure 5. Annual population trend estimates for Cassin’s Sparrow from Breeding Bird Survey 1966 - 1996

(Sauer et al. 1997)

BBS TREND MAP 1966 - 1996

In spite of this variation in temporal trend patterns at larger scales,

much of which may be related to the great variation in annual

distribution of this species, several basic evaluation criteria can be

identified to search for potential problems at smaller scales, such as at

the physiographic stratum level. Patterns in which early (1966 - 1979)

trends were level or increasing and later (1980 - 1996) and overall

(1966 - 1996) trends are declining would appear to be of more concern

than patterns where early declines or level trends are followed by

increases. In addition, trends that show up in the core of Cassin's

Sparrow range are more likely to raise concern than patterns on the

periphery where annual variations in distributions may be greater.

Using these criteria identifies the trends in Texas (Table 3) as a

potential area of concern. We observed the most significant downward

trend in Cassin's Sparrow numbers over the entire BBS time period,

and no clear pattern in either of the shorter time periods. By looking at

the trend patterns in individual physiographic strata (Table 3) within

Texas, one can get an idea of where the problems might be. The most obvious

pattern of concern is in the Edwards Plateau where there is a somewhat

Population Estimates and Trends
22 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

significant downward pattern in 1969 - 1979, followed by highly significant,

steep declines in 1980 - 1996 and across the entire time period. Of similar

concern are the patterns in the South Texas Brushlands where there was a

significant increase from 1966 - 1979, then a somewhat significant decrease

from 1980 - 1996, and an overall highly significant decline for the entire time

period (1966 - 1996). Figure 4b shows annual indices of abundance for these

and other physiographic strata. There are not any significant or consistent

trends to raise concern in the other physiographic strata in Texas with large

enough sample sizes to analyze for Cassin's Sparrow trends (Rolling Red Plains;

Staked Plains; Chihuahuan Desert). From this information, it would appear that

the declines in Texas, and possibly the survey-wide trends for this species, are

being driven primarily by declines in the Edwards Plateau and the South Texas

Brushlands.

Applying the same criteria to New Mexico, which is also within the

core of the Cassin's Sparrow's range, the BBS data show no significant

or consistent trends over time and neither do any of the physiographic

strata within the state (Table 3).

Possible Explanation Historic Landscape Change in Texas - The Edwards Plateau of

of Trends central and west-central Texas (Figure 6) covers about 93,240 square

kilometers (Riskind and Diamond 1988). It has undergone significant

landscape-level habitat changes in recent history. Prior to settlement,

most of the Plateau was a fire-maintained savannah whose principal

woody species was live oak (Quercus fusiformis). Due to intense,

confined grazing which removes fuel and reduces water infiltration

rates, and the resulting decreased fire frequency, the Plateau has

experienced widespread expansion of woody plants, especially Ashe

juniper (Juniperus ashei), resulting in dense stands locally known as

"cedar brakes" (Fowler and Dunlap 1986; Riskind and Diamond 1988;

Taylor and Smeins 1994; Fuhlendorf et al. 1997). The result is a

transformation from grassland and oak savannah communities to a

woodland dominated by juniper, oak, and mesquite. It has been found

that Ashe juniper has the potential to produce nearly closed canopy

stands where composition and diversity of flora (such as herbaceous

ground cover) and fauna can be greatly altered (Fuhlendorf et al. 1997).

However, Fuhlendorf et al. (1997) did find that the influences of Ashe

juniper are dependent on factors including the size of the juniper trees

and long-term grazing or browsing history (with appropriate browse

levels controlling some of its spread and negative effects). There is no

evidence that Cassin's Sparrows use the cedar brake habitats. In

Maxwell's study (1979) in the northwestern part of the Edwards

Plateau, of the two habitat types in which another juniper species

(Juniperus pinchotii) was the dominant tree - juniper-liveoak savannah

and scrub oak shrubland - one Cassin's Sparrow was observed during

the breeding season and winter in one year in the former, and none

were observed in the latter. These numbers are small in comparison to

those reported by Maxwell in more preferred habitats, as described in

the "Habitat" section of this report.

Population Estimates and Trends
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 23

Figure 6. Map of Texas showing Edwards Plateau and South Texas Brushlands

physiographic strata.

In addition to the threats posed by woody encroachment, there has

been substantial suburban development in the eastern and southern

parts of the Edwards Plateau (B. Ortego pers. commun.; K. Bryan pers.

commun.), with the Plateau becoming more important as a recreational

and second home area (USFWS 1992; Fuhlendorf et al. 1997). Counties

on the eastern Edwards Plateau surrounding Austin and San Antonio,

as well as smaller cities such as San Marcos and New Braunfels, are

experiencing population growth rates several times greater than the

U.S. average and projections are that it will continue (USFWS 1990;

USFWS 1992).

The South Texas Brushlands encompass about 8 million ha in the

southern tip of Texas (Figure 6), just south of the Edwards Plateau. In

presettlement times, much of south Texas was covered by grassland

with scattered groves of thorn forest (Rappole et al. 1986). However, as

a result of a combination of fire reduction and grazing pressures, by the

early 1900's there had been a considerable change in the grasslands,

with an increase in cacti and woody species on upland sites, an increase

in annual grasses, and a decrease in perennial grasses (Rappole et al.

1986), so that south Texas is described now as semiarid brushland. In

comparison with the Edwards Plateau, in the South Texas Brushlands, the

Population Estimates and Trends
24 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

threats posed to Cassin's Sparrows may actually be related to destruction of

brushland through conversion to agriculture, urban development, and brush

control, as opposed to shrub encroachment. For example, since the 1920's in

the Lower Rio Grande Valley (LRGV) (the southernmost part of the South

Texas Brushlands), more than 95% of the original native brushland has been

converted to agriculture or urban use (Jahrsdoerfer and Leslie 1988).

Brushlands have been converted through mechanical clearing, pesticides, and

fire. Large-scale removal of brush began in the early 1900's. By the early

1930's extensive mechanized brush removal began, developing methods

including tractors pulling large cables, heavy chains, rolling choppers, root plows,

brush mowers, and tree grubbers (Inglis et al. 1986). In the Rio Grande Plain

alone, more than 3,000 ha of brush/year were destroyed from 1930 to 1948;

more than 21,000 ha/year from 1949 to 1954; and almost 20,000 ha/year from

1955 to 1959 (Davis and Spicer 1965). From 1940 to 1981, Texas landowners

treated an average of 600,000 ha annually to remove thorn forest (Welch 1982).

In comparison to brushlands cleared for agriculture, rangelands that are

managed for brush will at least eventually return to less diverse brushlands with

a grass component. However, most efforts lead to a control-regrowth cycle of

five to ten years (Davis and Spicer 1965), and the land is often planted to exotic

buffelgrass (Pennisetum ciliare) to increase forage for livestock. This exotic

grass competes with native grass and forbs, greatly reducing habitat value for

birds, as well as other flora and fauna (Jahrsdoerfer and Leslie 1988). Finally,

urbanization poses an additional threat to the South Texas Brushlands. Using

the LRGV as an example again, human population has increased steadily since

the early 1900's, with the period from 1980 to 1990 expected to outgrow the

state average of 27% with a rate of 40% (Jahrsdoerfer and Leslie 1988).

HABITAT Although Cassin's Sparrows use slightly different habitats in different parts of

their range, the common denominator across all habitats seems to be that they

require both a grass component (usually short grass) and a shrub component.

The latter component may be actual shrub species [e.g., mesquite, sage

(Artemisia spp.), hackberry (Celtis spp.), rabbitbrush (Chrysothamnus spp.), or

oaks (Quercus spp.)] or other vegetative forms that approximate shrub

structure [e.g. yucca (Yucca spp.), paddle cacti (Opuntia spp.), ocotillo

(Opuntia spp.) or bunch-grasses] (Baicich and Harrison 1997; Rising 1996;

Williams and LeSassier 1968). The need for the structure provided by shrubs or

similar plants is related to the bird's need for perches from which to sing or

launch itself for its flight song and its frequent use of low shrubs for nest

placement. Schnase (1984) also noted that the mesquite thickets within

Cassin's Sparrow territories were distinctly preferred when fledglings were

present. It appears that relative proportions of grass and shrubs in acceptable

Cassin's Sparrow habitat cover a wide range from grassland habitats with a

very sparse distribution of shrubs to shrubland habitats with a grass cover

(JMR).

Population Estimates and Trends
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 25

See Appendix A for specific descriptions of the habitat used by Cassin's

Sparrows in individual states. See Appendix B for additional habitat descriptions

from primary references cited in sections below.

Specific research on habitat selection in Cassin's Sparrows has been limited and

much of it was conducted in southeastern Arizona habitats. This is worthy of

note since the application of these conclusions across the entire breeding range

of Cassin's Sparrow may not be warranted. The variation in habitats used

across their range is great, and Cassin's Sparrow response to habitat and

environmental change may also vary. Broad application of these results should

be done with care.

Breeding Season Results of studies conducted in semidesert grasslands in

Habitat Requirements southeastern Arizona at the Appleton-Whittell Research Ranch

(AWRR, also called the Audubon Research Ranch) and surrounding

land in Santa Cruz and Cochise Counties were consistent with the

"common denominators" mentioned above. A comparison of habitat

selection in three Aimophila sparrow species found that Cassin's

Sparrows were positively and significantly correlated with upland

mesquite grassland mesa habitat, as compared with sacaton

bottomlands, or ravine and slope habitats (Webb and Bock 1990). A

comparative study of grassland bird habitat preferences in the same

area found that Cassin's Sparrows were most strongly associated with

areas of high shrub canopy cover and density. They rarely occupied

plots with greater than 35% bare ground, and usually avoided areas

with less than 6% shrub canopy cover (Table 4). Compared to the

other species in the study, they preferred sites with more, taller grass

and less bare ground, and occurred more often near mesquite trees

(Bock and Webb 1984). See Appendix B for additional descriptions of

the upland grassland habitat at AWRR.

Table 4. Average characteristics of plots occupied by Cassin's Sparrows

(from Bock and Webb 1984).

Vegetative Characteristic Mean (SD)

Bare ground (%) 23.0 (±4.5)

Grass cover (%) 68.8 (±7.5)

Grass height (cm) 29.1 (±6.4)

Mean dist. (m) to 3 nearest mesquite trees 18.4 (±14.2)

Mesquite canopy (%) 03.7 (±3.3)

Shrub canopy (%) 10.3 (±5.5)

Shrub density (shrub/100 m2) 23.6 (±13.9)

Herb cover (%) 02.9 (±1.9)

Results from another set of studies on bird communities in

southeastern Arizona at the Santa Rita Experimental Range (SRER)

in Pima County might initially appear contradictory to those mentioned

above. In a comparison of avian communities in grassland habitat with

low mesquite density (called "grasslands") and habitats with high

mesquite density (called mesquite savannah), Maurer (1985) found that

Cassin's Sparrows were more common in the "grasslands" than in "mesquite

savannah" (Table 5). In a related paper focusing on habitat modeling, Maurer

Habitat
26 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

(1986) found that Cassin's Sparrows were positively associated with greater

ground cover and grasses typical of healthy ranges, and were negatively

associated with mesquite trees and grass species characteristic of poor range

conditions (e.g., Rothrock grama (Bouteloua rothrockii) - they tended to avoid

areas of high mesquite density and low grass cover. See Appendix B for

additional descriptions of the habitat at SRER.

Table 5. Densities of singing males per square km in two habitat types (from Maurer 1985).

Year Mesquite Savannah Grassland

1982 4.9 43.2

1983 34.5 71.2

A closer look at these papers indicates that they may not really be

contradictory. I believe that the AWRR and the SRER are located at

different places along a habitat continuum, with the AWRR found at

one end of the continuum described as upland grasslands with a low

density of large shrubs and mesquite, and the SRER at the other end

described as a desert shrubland with high mesquite densities and

varying amounts of grass ground cover. In this light, the combined

results may actually tell us more about Cassin's Sparrow habitat use,

rather than showing conflicting results. It is possible that at the

AWRR, since Cassin's Sparrows require a shrub component in their

habitat and very few shrubs were available, they preferred sites with

more mesquites. By comparison, at the SRER where plenty of

mesquite are available but Cassin's Sparrows also require a grass

component, the birds preferred sites with relatively lower mesquite

density. In fact, Maurer (1986) states that there is generally a negative

relationship between mesquite density and grass productivity at

SRER. In other words, Cassin's Sparrows require a shrub component

within grasslands, but if shrub density becomes too great, there is no

longer a grass component under/between the shrubs to meet the

species' other need. Although it is not possible to confirm this by

comparing shrub densities due to lack of compatible data in the two

manuscripts, scrutiny of the literature and personal conversations with

individuals familiar with these areas (D. Krueper pers. commun.; C.

Bock pers. commun.) support this hypothesis.

A study of breeding biology in south-central Texas found that all

Cassin's Sparrow territories included some combination of dense

mesquite thicket and open, grassy areas with scattered cacti and small,

shrub mesquite trees. An average of 28.4% of individual territories was

composed of mesquite thickets (Schnase 1984). Another study in the

same area (Maxwell 1979) compared bird densities from September

1975 to June 1977 in eight different plant communities - riparian forest,

juniper (Juniperus spp.)-live oak savannah, scrub oak shrubland,

bottom mesquite woodland, upland mesquite woodland, defoliated

mesquite shrubland, scrubby mesquite grassland, and grassland. He

found the highest breeding densities of Cassin's Sparrows in scrubby

mesquite grassland (33 birds per 40.4 ha in 1976 and 20 birds per 40.4 ha

in 1977). He described this habitat as having an absolute shrub density of 717/

ha, a relatively low foliage height diversity (0.540), the lowest percent vegetative

Habitat
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 27

cover (92%) of all sites, a foliar ground cover from 0.3 to 1.2 m of 22% and

from 1.2 to 3.1 m of 1%. They were also found in lower densities in bottomland

mesquite woodland (6 and 1/40.4 ha), upland mesquite woodland (7 and 8/40.4

ha), grassland (7 and 11/40.4 ha), and defoliated mesquite (7 and 11/40.4 ha).

Winter surveys found only a few Cassin's Sparrows in upland mesquite

woodland (2/40.4 ha in 1977), and juniper-live oak savannah (1/40.4 ha in 1977).

Maxwell states that Cassin's Sparrows are found from open grassland through

all stages of mesquite succession, being most common in scrubby mesquite

grasslands and, as mesquite increases in stature and density, Cassin's Sparrows

decrease in abundance and eventually abandon the site. See Appendix B for

additional descriptions of the habitat at these sites.

A study conducted in southern New Mexico and central Chihuahua

(Meents 1979) focused primarily on total bird community measures, but

provided some species-specific information. Cassin's Sparrows were

present on all four sites during the breeding season, but were most

abundant at the La Campana site in northern Chihuahua (mean birds

per roadside census = 74.0); values for the three southern New Mexico

sites were 14.5, 17.4 and 8.0 respectively. Although she did not evaluate

individual species associations with habitat, her characterizations of

vegetation at the four sites indicate that the La Campana site had

higher shrub cover - 8.4 % (± 5.6) - as compared with the other sites

which had 0.5 % (± 0.5); 0%; and 0% respectively. Percent grass and

forb cover appeared quite similar. This lack of shrub component at the

other sites may explain the smaller numbers of Cassin's Sparrows

found there during the breeding season. La Campana was the only site

where Cassin's Sparrows were found in the winter, and there in

extremely small numbers (mean birds per roadside census = 1.0). See

Appendix B for additional descriptions of the habitat at these sites.

A study of grassland bird habitat use on the Comanche National

Grasslands in Colorado found that sites where Cassin's Sparrows were

detected could be characterized by 27% bare ground, 14.8% shortgrass,

37.8% midgrass, 8.5% forbs, 2.4% cholla, 4.6% yucca, 0.9% low shrub (<1

m), and 4.1% tall shrub (>1 m) (Gillihan 1999).

Winter Habitat Very little research has been done to define the wintering habitat of

Requirements Cassin's Sparrow. Rising (1996) reports that in the winter they occur in

habitat very similar to their breeding habitat, but only in the southern

part of their U.S. range. Kaufman (1996) reports that in migration and

winter, they are found in pure grassland, brushy areas, and deserts. On

the wintering grounds in Texas, Cassin's Sparrows in desert areas seek

brushy draws and canyons, while in southern Texas they use pricklypear cactus (Opuntia sp.) and thick brush that dot savannahs

(Oberholser 1974). K. Bryan (pers. commun.) stated that Cassin's

Sparrows used a more limited set of habitat types in the winter in

Texas than they did while breeding. He felt they were using the

thickest, well-developed grassland with a shrub mosaic, and although

they were in the Trans-Pecos in the winter, they weren't using the

desert scrub that they did during breeding season. In southeastern Arizona,

Cassin's Sparrows occupy small grassy cienegas in lowland desert flats

Habitat
28 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

otherwise dominated by creosote bush (Larrea tridentata). These cienegas

have dense grass coverage, with scattered mesquite and other shrubs (J.

Dunning pers. commun.).

A study of the size and structure of wintering avian communities in

seven habitat types in south Texas, found that Cassin's Sparrows occurred in

three habitat types -- open brushland (60% grass/forbs and 10% low shrubs),

dense brushland (50% grass/forbs and 30% low shrubs), and two-layered

brushland (50% grass/forbs, 30% low shrubs, and 10% tall shrubs). These

three habitat types could be defined as grassland/shrub habitats along a

continuum from grass with scattered patches of dense shrubs and mesquite, to

dense shrubland with a layer of taller mesquite and acacia shrubs above the

dominant shrub layer. Cassin's Sparrows were not found in grass-forb prairies

(100% grass/forbs), scrub grasslands (60% grass/forbs, 40% creeping brush

and no shrubs), oak woodlands, or riparian forest. (Emlen 1972). See Appendix

B for additional descriptions of the habitat at these sites.

A study of distribution patterns and habitat associations of wintering

grassland birds on the Mexican Plateau (Carter et al. 1997; Carter et al.

1998) found that Cassin's Sparrows were found on plots with more than

average shrub cover, bare ground, litter, and tall grass.

MANAGEMENT Because Cassin's Sparrows are very responsive to vegetative structure and

grass/shrub components of their habitat (see above), they are potentially

affected by a number of management practices including grazing and shrub

control. However, reaching any conclusion about the effects of various

management practices or environmental conditions on Cassin's Sparrows is

difficult due to the limited literature on this subject. As mentioned elsewhere in

this report, there have been several studies each on grazing, fire, and exotics

impact on Cassin's Sparrows and other grassland birds, but they have focused

on a small area that arguably could be called the periphery of the species' range

- southeastern Arizona. Therefore, any application of this information to other

parts of Cassin's Sparrow range should be done with caution.

See Appendix B for additional habitat descriptions from primary

references cited in sections below.

Grazing There are definite reasons to view the existing literature regarding

Cassin's Sparrow responses to grazing with caution. As Saab et al.

(1995) state, ". . . birds respond differently to livestock grazing in

different places. The same amount of grazing that can be used to create

ideal habitat for a species in a tallgrass prairie may be equally certain to

destroy that same species' habitat in a shortgrass steppe or semidesert

grassland. Therefore, management recommendations, derived from

(synthesized) data . . . should be tailored to the various sorts of

grasslands involved." In fact, they go on to single out Chihuahuan

Desert grasslands as an example of climatically stressed habitats

where environmental perturbations like grazing can result in conversion into

desert shrublands. Although the grasslands of southeastern Arizona cannot

technically be classified in this group, they certainly represent arid grasslands

that may be more susceptible to grazing impacts than Cassin's Sparrow habitat

Habitat
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 29

in other parts of its range. In light of the evidence of Cassin's Sparrow

distributional response to changes in precipitation, it seems likely that it is a

species for which a particular grazing regime or intensity may have very

different effects under different vegetation or precipitation conditions. It is

certainly the case that some habitats within the core of Cassin's Sparrow

habitat, such as eastern New Mexico, are almost all grazed, and yet continue to

support substantial Cassin's Sparrow populations (JMR).

The effects of grazing on Cassin's Sparrows can be addressed at

two levels. The most obvious is the direct and immediate effect

of grazing on the habitat structure preferred by Cassin's

Sparrows - reduction of vegetative height and density, or

changes in species composition through grazing preference. Most

of the information presented here falls in that category.

Knopf (1996), in his discussion of endemic grassland birds and their

distribution across grassland habitats in the west, places Cassin's

Sparrows at the mixed grass to mixed grass/shrub end of a

bareground-shortgrass-mixed grass-mixed/shrub habitat continuum,

and at the moderate-light-none end of an excessive-heavy-moderatelight-none continuum representing historical (bison) grazing patterns.

He states that breeding habitats of Cassin's Sparrow were probably

outside the distribution of historically large herds of bison on the plains.

A study comparing breeding grassland bird use of southeastern

Arizona grasslands on grazed and ungrazed land (Bock and Webb 1984)

concluded that Cassin's Sparrows were excellent indicators of lightly

grazed or protected range, but only where shrubs or small trees are

present. Over two breeding seasons, Cassin's Sparrows were found

only on ungrazed sites (Table 6a). Both Cassin's Sparrows and

Grasshopper Sparrows were found to occupy areas with more and

taller grass cover and less bare ground than did Horned Larks

(Eremophila alpestris) and Lark Sparrows (Chondestes grammacus)

(Table 4).

Another study of grazed and ungrazed sites in the same area (AWRR

and an adjoining ranch) during the breeding and nonbreeding seasons

(Bock et al. 1984) found that Cassin's Sparrows were significantly more

abundant on ungrazed plots than on grazed plots in both breeding and

winter seasons (Table 6a). In fact, in both cases this species was only

found on ungrazed sites. The amounts of ground cover and shrub cover

were major determinants of the bird communities. The ungrazed plots

supported 45% more grass cover, a comparatively heterogeneous grass

community, and significantly more herbaceous cover than did grazed

plots (Table 6b). Woody plants were significantly more abundant

overall on ungrazed plots (although mesquite was uncommon throughout and did

not differ between treatments), and various individual shrub species were

denser and/or larger on the ungrazed plots (showing evidence of cattle browsing

on grazed plots). An extension of this study, including an additional site and

additional year of data, confirmed the above results (Tables 6a and 6b) –

although some Cassin's Sparrows were found on grazed plots, they were

Management
30 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

significantly more abundant on ungrazed upland grassland sites across seasons

(Bock and Bock 1988).

Table 6a. Results of three related studies comparing Cassin's Sparrow responses to grazing in

southeastern Arizona (Bock and Webb 1984; Bock et al. 1984; Bock and Bock 1988).

* significantly greater than other treatment P < 0.01; ** P < 0.001.

Source Ungrazed Grazed

1. Bock and Webb (1984)

Mean birds/plot

Breeding season 1981 (n = 9) 4.0 (±2.0)* 0

Breeding season 1982 (n = 14) 2.2 (±1.0)* 0

2. Bock et al. (1984)

Total birds/treatment

Breeding season (n = 2) 66** 0

Wintering season (n = 2) 42** 0

3. Bock and Bock (1988)

Total birds/treatment

Across seasons (n = 4) 209** 19

Table 6b. Results of two related studies describing effects of grazing on vegetative cover in

southeastern Arizona (Bock et al. 1984; Bock and Bock 1988). Asterisks (*) indicate

treatment significantly greater than other treatment * P < 0.05; ** P < 0.001

Source Vegetation Category Ungrazed Grazed

Bock et al. 1984 Percent Ground Cover

Grasses - total 80.4** 55.6

Herbs - total 12.0** 5.6

Woody plants - total 13.5 11.5

Bare ground 17.6 34.6**

Woody plant numbers

Total woody plants/plot 37.6** 9.5

Bock and Bock 1988 Percent Basal Area Cover

Grasses 52.0* 36.0

Herbs 13.0 10.0

Shrubs 6.0* 1.0

Bare ground 27.0 51.0**

An unpublished study of bird community responses to the removal of

cattle from the BLM's San Pedro Riparian National Conservation Area

in southeastern Arizona found that Cassin's Sparrow density increased

from 1986 (before cattle were removed), through 1987 (when they were

removed), to 1991. This response appears to be related to changes in

sacaton-mesquite habitats along the river following cattle exclusion -

foliage volume at several levels increased substantially during this time period

(D. Krueper written commun.).

Although not supported by particular documentation, Sutton (1967)

describes preferred Cassin's Sparrow habitat in Oklahoma variously as

"moderately" or "lightly" grazed sand prairie with a scattered shrub component.

Management
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 31

The second and related question regarding the effects of grazing is, what are

the more long-term effects of grazing on the landscape and subsequently on

Cassin's Sparrow habitat? The complicated nature of grassland ecology,

especially as it applies to different types of grasslands, is beyond the scope of

this document. However, in general it is recognized that the long-term result of

grazing in many southwestern grassland habitats is a significant reduction of fuel

loads and a subsequent reduction in the frequency and intensity of fire that,

historically, has controlled the invasion of woody shrubs into grassland

ecosystems (McPherson 1995; Wright and Bailey 1982). It is possible,

therefore, that in grassland habitats with insufficient shrub component to support

Cassin's Sparrows, grazing may result in increased shrub cover and therefore

increased Cassin's Sparrow habitat. In comparison, in shrubland habitat an

increase in shrub density that results in insufficient grass ground cover, may

reduce or degrade preferred Cassin's Sparrow habitat. Documenting such

connections would be extremely difficult, however, and caution should be

exercised in applying such ideas to management because of the potential mixed

impacts on other species.

Burning Most literature regarding Cassin's Sparrow responses to fire addresses

the short-term issue of its response to the direct, immediate effects of

fire on a habitat. A comparison of bird communities in burned and

unburned sacaton grasslands in southeastern Arizona (Bock and Bock

1978) found that total bird populations responded dramatically to

summer burns with large numbers of seed-eating birds, including

various sparrows, concentrating on the burns in the first two postburn

years. The effect of the fires on vegetation was to reduce sacaton cover

and greatly increase herb production through two postfire growing

seasons. Although this study did not conduct statistical analyses of

individual species numbers, the data presented for Cassin's Sparrow

numbers indicate this same pattern. The differences may have been

even more dramatic since data were collected throughout the year and

pooled to arrive at mean bird numbers. This method also precludes any

conclusions about seasonal differences in habitat use. A review of this

study (Bock and Bock 1988), using some different analyses, found that

Cassin's Sparrows were significantly more abundant on the burned

sacaton plots (P < 0.001) than on the unburned plots.

In comparison, a study comparing bird community response to wildfire

in native and exotic grasses (Bock and Bock 1992) presents a more

complicated picture that initially appears to contradict some of the

above results. However, although this study was also conducted at the

AWRR, it was conducted on upland mesa grasslands, which Cassin's

Sparrows prefer (Webb and Bock 1990), rather than the very different lowland,

sacaton grasslands studied in Bock and Bock (1978). A fire in July 1987

significantly reduced grass cover through two years on both native and exotic

sites, did not alter the proportion of exotic grass cover in the exotic plots,

reduced shrub cover, and resulted in an increase in herbaceous growth. Total

bird numbers in the fall increased dramatically on burned plots in both native and

exotic grasses for two postfire seasons. However, Cassin's Sparrows were

uncommon in the fall and did not show any significant responses to burns. For

breeding Cassin's Sparrows, results were clearest in native grasses, where

breeding Cassin's Sparrows were significantly less abundant on burned native

Management
32 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

grasslands for two postfire years (Table 7). It appears that during the breeding

season they preferred burned to unburned exotic grasses, but their response to

burns in exotic grasslands may have been confounded by an apparent reduction

in numbers of Cassin's on unburned exotic grasslands over the period of the

study (Bock and Bock 1992).

Table 7. Total numbers (means and SD) of birds recorded cumulatively on summer and winter

counts on 50 m diameter plots in burned and unburned native and exotic grassland in

southeastern Arizona - fire occurred July 1987 (Bock and Bock 1992). * values for burned

and unburned significantly different within grassland type P < 0.01; ** P < 0.001

Season Year Native grass Exotic grass

Burned Unburned Burned Unburned

 (n =14) (n =14) (n =11) (n =11)

Breeding 1984-85 1.18 (±0.60) 1.2 9(±0.47) 0.46 (±0.52) 0.21 (±0.43)

(May-Aug.) 1987 0.00* 0.86 (±0.77) 0.00 0.14 (±0.36)

1988 0.55 (±0.52)** 1.86 (±0.77) 0.64 (±0.51)** 0.00

1989 1.55 (±0.93) 1.36 (±0.84) 0.91 (±0.54)** 0.00

1990 1.09 (±0.94) 1.29 (±0.61) 0.46 (±0.52)* 0.00

Winter

(Sept-Nov.) 1984 0.36 (±0.51) 0.29 (±0.61) 0.18 (±0.60) 0.00

1987 0.00 0.14 (±0.36) 0.09 (±0.30) 0.14 (±0.36)

1988 0.18 (±0.62) 0.43 (±0.65) 0.00 0.00

1989 0.09 (±0.30) 0.07 (±0.27) 0.00 0.00

1990 0.36 (±0.51) 0.29 (±0.47) 0.00 0.00

In a study of the effects of fire on grassland birds on the Buenos Aires

NWR, Gordon (In Press b) found that Cassin's Sparrows were

significantly more abundant on unburned plots (n = 3) than burned

plots (n = 3) in the first postburn year, even though there had been no

significant difference in abundance between plots previous to the burns.

During additional bird monitoring surveys conducted on the Buenos

Aires NWR (A. Flesch written commun.), data were collected on

sparrow use of plots with different fire histories. Flesch provided the

following observations, which are consistent with the pattern found by

Bock and Bock (1992) for breeding Cassin's Sparrows in native grasses.

Cassin's Sparrows were not as abundant on first-year postfire, and

perhaps second-year postfire plots. In 1997, no Cassin's were detected

on plots that had been burned that spring. In 1998, several singing

males were found on plots that had been burned 3.5 months earlier.

Flesch suggests that the presence of some Cassin's Sparrows on burned plots in

1998 was due to the unusually high rainfall received in late winter and early

spring 1998, resulting in more rapid grass regrowth.

The second level at which fire can affect Cassin's Sparrows is by its

long-term effect on habitat type. It is widely recognized that fire

interacts with other factors (e.g., soil, herbivory, vegetation type) to

restrict woody plant establishment in grasslands and that fire

suppression resulting from reductions in fuel loads, especially from

grazing, in the most extreme cases may result in transformation of

grassland to shrubland (McPherson 1995; Wright and Bailey 1982). Although

Cassin's Sparrows do require a shrub component in their habitat, dense woody

Management
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 33

shrublands without a substantial grass cover provide less than ideal Cassin's

Sparrow habitat (Maurer 1985; Maurer 1986).

Conservation Reserve A study of the value of CRP lands to breeding nongame birds in the

Program Lands Texas Southern High Plains (southern part of the Panhandle) found,

(CRP) not surprisingly, that these plantings were valuable habitat for

grassland birds in a landscape dominated by farms and cropland

(Berthelesen and Smith 1995) – only two nongame bird nests were

found in crop fields. A comparison was made of bird use in the most

commonly established CRP cover types – blue grama (Bouteloua

gracilis)/side-oats grama (B. curtipendula); blue grama/Kleingrass

(Panicum coloratum); and blue grama/plains bluestem (Bothriochloa

ischaemum) mixtures. In one year, Cassin's Sparrow nest density/acre

was significantly higher in blue grama/side-oats grama mixtures than

in the other two. The second year showed no significant differences,

and nest densities between years in the blue grama/side-oats grama

mixtures were significantly different. Insufficient data precluded

comparison of nest success estimates between different CRP cover

types, but pooling did find a significant difference in nest success

estimates (using the Mayfield method) and clutch sizes for Cassin's

Sparrows between years.

Tamarisk Tamarisk, or salt cedar, is an exotic that was originally introduced into

the United States from Eurasia for ornamental and soil erosion control

purposes. It has escaped and spread throughout riparian habitats in

the Southwest, where it has demonstrated remarkable adaptability and

competitiveness with native plants under the arid, saline conditions

often found due to water control practices. It has resulted in many

management disagreements related to its wildlife benefits and the

potential impacts of control activities.

A study along the middle Pecos River in New Mexico, designed to

establish baseline data on the effects of tamarisk removal on breeding

bird communities (Livingston and Schemnitz 1995), found that Cassin's

Sparrows were most abundant in grasslands with mixed shrubs

(including tamarisk), and used this habitat as well as grasslands devoid

of tamarisk (in this case alkali sacaton grasslands) more than sites with

dense stands of tamarisk.

Another study of avian use of tamarisk on the middle Pecos River

Valley (Hunter et al. 1988) found that Cassin's Sparrows did not use

any of the riparian habitat types during the winter. However, in the

breeding season, a few Cassin's Sparrows were found using honey

mesquite (3/40 ha) and tamarisk (1/40 ha) habitat, where these species

provided a shrub component but minimal upper canopy and middle

canopy structure. They were not found in the two types of cottonwoodwillow habitats.

A more thorough study of avian habitat use along the Pecos River from

1979 to 1981 (Hildebrandt and Ohmart 1982) found more evidence

comparing Cassin's Sparrow use of tamarisk and other habitats.

Management
34 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

Using density estimates from two summer periods - June to July, and August to

September - they found the following data for Cassin's Sparrows: no birds in

the densest two tamarisk-dominated habitats that provided substantial canopy

structure (substantial foliage from 4.6 to 7.6 m, and substantial foliage from 1.5

to 4.6 m respectively); six to seven birds per 40 ha for tamarisk habitat with little

foliage above 3 m; and 16 to 24 birds per 40 ha for sparse (little foliage above

1.5 m) tamarisk habitat. For comparison, they found 6 - 12 birds per 40 ha in

sparse four-winged saltbush habitat; 6 - 12 birds per 40 ha in sparse honey

mesquite habitat; two to seven birds per 40 ha in cleared communities

dominated by weeds and shrubs; and three to four birds per 40 ha in cleared

communities dominated by grass.

THREATS

Habitat Cassin's Sparrows are shrub-grassland specialists. The loss of

grasslands with a shrub component through conversion to agriculture,

suburban development, and desert scrublands (Welch 1982; Fowler and

Dunlap 1986; Jahrsdoerfer and Leslie 1988; Riskind and Diamond 1988;

Taylor and Smeins 1994; Fuhlendorf et al. 1997; U.S. Census Bureau

1999a) is the primary threat to Cassin's Sparrow habitat. Over-grazing

and poor rangeland management also contribute to the loss of Cassin's

Sparrow habitat (Bock et al. 1984; Bock and Bock 1988). Regulation of

Cassin's Sparrow populations could also be influenced by other factors

(e.g., habitat fragmentation, plot size, etc.) or by the same factors

occurring on wintering grounds or during migration. However, we

know little about these issues.

Overutilization for No evidence was found to suggest that direct use of this species for

Commercial, Recreational, commercial, recreational, scientific, or educational purposes poses a

Scientific, or Educational threat.

Purposes

Disease or Predation No records were found to suggest that disease is a particular threat to

Cassin's Sparrow populations.

There were few records regarding predation upon this species.

Williams and LeSassier (1968) note records of predation by a shrike

(Lanius spp.), snakes, and possibly red ants (a nest was discovered in

which nestlings were consumed by red ants although it was uncertain

whether they killed the nestlings or simply consumed them when they

were already dead). Schnase et al. (1991) cited indirect evidence that predation

may be high in Cassin's Sparrows; they reported that only 54% of the eggs laid

were successfully fledged by birds in their study. Cassin's Sparrows

occasionally enter rodent burrows to escape predation (Bowers and Dunning

1985). Montoya et al. (1997) studied avian predation and the diet of Aplomado

Falcons (Falco femoralis) in Mexico and found that, although Cassin's

Sparrows were a relatively common potential prey item in the area, they were

not found in falcon pellets or prey remains. They suggested that Cassin's

Sparrows might have been too small as prey items when the most common

available species and prey species were meadowlarks (Sturnella spp.).

Management
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 35

Inadequacy of Existing Current regulations directed at protection of bird populations and

Regulatory Mechanisms individuals appear to provide adequate protection for Cassin's Sparrows in the

United States. It is protected under the Migratory Bird Treaty Act of 1918 in

the U.S. In Mexico the species is protected under the Convention for the

Protection of Migratory Birds and Game Mammals of 1936.

However, there is no regulatory protection for Cassin's Sparrow

breeding or wintering habitat in the United States or Mexico. There

are specific locations that are protected for a variety of uses and

wildlife resources (e.g., National Grasslands, state Wildlife

Management Areas, and other federal, state, and private land

holdings), but none of these are focused particularly on the needs of

Cassin's Sparrows, such as habitat. Incentive programs like the

Conservation Reserve Program (CRP) may provide suitable habitat for

Cassin's Sparrows if certain plantings are used (Berthelsen and Smith

1995), but there are no particular recommended management practices

provided at this time. One exception is a recent set of best

management practices, including some for Cassin's Sparrows, provided

by the Colorado Bird Observatory to the Comanche National

Grasslands in Colorado (Gillihan 1999).

Other Natural or

Manmade Factors Pesticides - Pesticides have not been documented as a threat.

Population size - Although there is little reliable information on

current population size, and the secretive nature and large seasonal

variations in local populations make drawing conclusions difficult,

populations are broadly believed to remain high in many parts of its

range. At this time, there is no evidence to suggest that small

population size itself poses a threat to this species' survival.

Nest Parasitism - Cassin's Sparrows are considered uncommon

cowbird hosts (Friedmann 1963). All records provided by Friedmann

(1963) were from Texas; he did acknowledge that it was possible that

Cassin's Sparrows seem to be an uncommon host because their nests

are so difficult to find and therefore evidence of parasitism is also rarely

documented. Kingery and Julian (1971) reported a Cassin's Sparrow

nest containing three Cassin's Sparrow eggs and one Brown-headed

Cowbird (Molothrus ater) egg on the Comanche National Grasslands in

Baca County, Colorado. Schnase (1984) observed three nests parasitized by

Brown-headed Cowbirds, each with four Cassin's Sparrow eggs and one or two

cowbird eggs; two were subsequently abandoned, and the third, from which the

cowbird egg was removed, fledged one young. Hunter and Howe (unpub.

man.) report a nest with two Cassin's Sparrow young and one cowbird that

fledged, and adults feeding fledgling cowbirds nearby at the same time, south of

Artesia, New Mexico in June 1980.

Suburban development - In light of Cassin's Sparrow requirements

for a relatively "natural" habitat composed of a mixture of grass and

shrubland, habitat degradation and loss due to suburban development

has the potential to negatively affect this species. Although not

specifically focused on Cassin's Sparrow habitat, two studies on the impact of

Threats
36 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

suburban development on native bird communities in southern Arizona indicate

the general impact such activities have on southwestern bird communities. Both

found that, although higher bird densities were found on suburban sites, 52 to

72% of the total density was composed of three or four exotic species, and

certain native desert species were not present (Emlen 1974; Rosenberg et al.

1987). Suburban development usually results in an increase in landscaping with

exotic plants and a decrease in native plant species. Mills et al. (1989) found

that in Tucson, native bird species richness and densities of native territorial

species were strongly correlated with the volume of native plant species and

lacked any correlation with exotic plant species volume. These results suggest

that similar threats are faced by Cassin's Sparrows, since their habitat

preferences are not compatible with the normal habitats provided in suburban

development.

The suburban growth occurring in many parts of the southwestern

U.S. makes this a real threat. The U.S. Census Bureau (1996) projects

(using the middle series projections) that the resident population of the

United States will increase by approximately 26.3 % from 1996 to 2025.

In comparison, four of the states within the Cassin's Sparrow range

show U.S. Census Bureau projections (1999a) exceeding the national

average for the same time period: New Mexico (55.0 %); Arizona (52%);

Texas (45.2 %); and Colorado (38.5 %). The U.S. Census Bureau

recently released additional information about the growth rates in

specific cities from 1990 to 1998 (U.S. Census Bureau 1999b), stating

that smaller cities experienced the fastest growth. On average, cities

containing at least 10,000 people grew 6.6% between 1990 and 1998;

cities with populations of more than one million in 1998 grew by 3.5 %;

and cities with populations between 10,000 and 50,000 grew the fastest

(8.6 %). In comparison to these national averages, the following cities

within the Cassin's Sparrow range exceeded the national averages

(U.S. Census Bureau 1999c), exemplifying the potential habitat

destruction posed by the expected suburban sprawl related to this

growth: Laredo, TX (43%); New Braunfels, TX (33.6 %); Brownsville,

TX (28.8 %); McAllen, TX (27.1 %); Deming, NM (27.1%); Las Cruces,

NM (22%); Santa Fe, NM (20.1 %); El Paso, TX (19.3 %); Austin, TX

(17%); Sierra Vista, AZ (15.4 %); San Antonio, TX (14.1 %); Del Rio, TX

(14%); Nogales, AZ (13.1 %); Silver City, NM (12.9 %); Las Vegas, NM (11.8

%); Midland, TX (11.5 %); Tucson, AZ (10.8 %).

Exotic grasses - A study of the ecological effects of exotic lovegrasses

(Eragrostis sp.) on the AWRR (Bock et al. 1986; Bock and Bock 1988)

found that total bird abundance was significantly greater on native

grass sites than on exotic grass sites in both summer and winter.

During the breeding season Cassin's Sparrows were significantly more

abundant on native grass plots than on exotic plots. In winter the

pattern was the same but it was not statistically significant. The study

found that native grass cover, native herb canopy, herb species

richness, shrub density, and shrub canopy were significantly reduced on

plots dominated by exotic grasses. Total grasshopper numbers were

signficantly reduced on exotic plots, an important observation since

Cassin's Sparrows consume substantial numbers of grasshoppers in the

Threats
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 37

breeding season (Bock et al. 1986). A study on effects of burns on native and

exotic grassland communities (Bock and Bock 1992), found that Cassin's

Sparrows appeared to avoid both burned and unburned exotic lovegrasses

(Table 7).

Grazing - There is evidence that in the southwest portion of its range, Cassin's

Sparrows are negatively affected by grazing. However, there have been no

similar studies conducted in the core of its range or on the eastern edge to

determine whether the different vegetation and precipitation characteristics

found there result in different responses to grazing.

Burning - With a few exceptions (e.g., sacaton grasslands), Cassin's

Sparrows will avoid burned sites for one or two years, probably due to

the temporary reduction in grass and shrub structure. However, from

a long-term perspective, burning Cassin's Sparrow habitat may have a

positive effect if it results in less dense shrub cover and, if fire

management permits a mosaic of burned and unburned sites, in the

short-term Cassin's Sparrows will not be negatively affected.

Brush Control - In light of Cassin's Sparrow requirements for a shrub

component in their habitat, programs to promote brush or shrub

control to benefit grazing have a potential to negatively impact this

species. However, their response is probably dependent on the

particular circumstances in specific locations - complete shrub removal

would likely have a negative impact, while reduction in shrub density

may be beneficial in some circumstances.

Unfortunately, no studies were found that specifically described the

response of Cassin's Sparrows to brush control practices. However, on

the SRER (Maurer 1985; 1986), the sites described as having lower

mesquite density were sites where mesquite control efforts had been

implemented. It was these sites that were preferred by Cassin's

Sparrows (see description in Breeding Habitat section), suggesting that

in some cases, where the shrub component has become too dense for

optimal habitat, shrub control may benefit the species.

Oberholser (1974) provides some observations about the history of

brush control in Texas. He suggests that Cassin's Sparrow habitat has

actually increased since 1933 when the Soil Conservation Service began

to subsidize ranchers for brush control. By 1968 brush removal had

been attempted on much of this species' range in the western two

thirds of Texas. In cases where clearing was followed by a regrowth of

native grasses and a sprouting of young mesquites and low bushes,

Cassin's Sparrows have benefitted. However, more efficient

mechanical and chemical means of extirpating all woody vegetation

have been developed (Oberholser 1974) that are effective at much

larger scales than initial efforts. In addition, native grasses are being

replaced with foreign plants (Rising 1996; Oberholser 1974), posing new

threats to this species.

Threats
38 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

Tamarisk - At least in some areas, where tamarisk habitat provides a shrub

component without a substantial canopy, it can be used by Cassin's Sparrows.

However, tamarisk habitat significance for Cassin's Sparrows is minimal since

tamarisk is a riparian species and Cassin's Sparrows are only found in a few

riparian habitats (e.g., bottomland sacaton grasslands), and it provides no threat

to Cassin's Sparrows.

ASSESSMENT

RECOMMENDATION

Recommendation The recommendations presented in this section have been jointly

on Current Status developed by the author and Stephanie L. Jones, USFWS Region 6

Nongame Migratory Bird Coordinator, and Bill Howe, USFWS

Region 2 Nongame Migratory Bird Coordinator, after review of the

contents of this document.

Existing information warrants neither a conclusion that the Cassin's

Sparrow range-wide population is in serious decline, nor dramatic

range-wide conservation measures. In fact, BBS data indicate that in

the core of its range in New Mexico it is very abundant and its

population is relatively stable. Therefore, we recommend no change in

Cassin's Sparrow official status at this time.

However, there is evidence of serious population declines in certain

parts of Texas (Edwards Plateau and South Texas Brushlands),

apparently due to major habitat loss and degradation. These declines

are associated with landscape-level habitat changes due to ongoing

woody encroachment, agricultural and suburban development, and

shrub control activities. Fluctuations in Cassin's Sparrow numbers

from year to year at a particular site appear to be associated with its

response to precipitation-related habitat conditions, and may confound

efforts to understand population trends. And, lack of information about

Cassin's Sparrow population trends in Mexico omits a substantial

portion of the species' range-wide population. Additional information

about population trends in the Edwards Plateau and South Texas

Brushlands as well as Mexico, and about causes of local, annual

population fluctuations, would be valuable in supplementing BBS data

and focusing more localized conservation efforts.

There also remain substantial gaps in our knowledge of this species' natural

history and ecology. There is no question that Cassin's Sparrows are adversely

affected by loss of shrubby grassland habitat to cropland or suburbs, but our

understanding of the effects of grazing and other rangeland management

activities on remaining habitat is less clear. There is evidence that Cassin's

Sparrows are negatively affected by heavy grazing in the most arid,

southwestern part of their breeding range, but additional comparative studies are

recommended to deter-mine their responses to types and levels of rangeland

management in the core of their range. In addition, there is very little

information available regarding their wintering or migration ecology, or their

breeding ecology in Mexico.

The threats to this species still exist. Based on current land use and

population growth patterns, the factors negatively affecting its populaThreats
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 39

tions in the Edwards Plateau and South Texas Brushlands promise to increase

and spread, even into the core of its range. Therefore we recommend

maintaining the Cassin's Sparrow as a species of special concern, monitoring its

status, and promoting research and monitoring to expand our knowledge of its

ecology, status, and responses to management activities.

CONSERVATION Cassin's Sparrow is a member of a guild of species that are dependent on the

health and availability of shrubby, arid grasslands. Other species could benefit to

some degree from conservation efforts aimed at Cassin's Sparrow breeding

habitat, although details of their natural history, range, and habitat requirements

will vary. These other species include Grasshopper Sparrow, Loggerhead

Shrike (Lanius ludovicianus), Botteri's Sparrow, Western Meadowlark

(Sturnella neglecta) and Eastern Meadowlark (S. magna). Many additional

species that rely on the same arid grasslands within the Cassin's Sparrow's

winter range would also benefit from conservation efforts there. These include

Vesper Sparrow, Baird's Sparrow, Savannah Sparrow, Lark Bunting

(Calamospiza melanocorys), Chestnut-collared Longspur (Calcarius

ornatus), and Brewer's Sparrow.

Cassin's Sparrow numbers fluctuate dramatically from year to year at

any particular site. This appears to be associated with its response to

fluctuating habitat conditions and climate, particularly precipitation.

These dramatic distributional changes suggest a species that might be

able to find suitable habitat wherever it exists within the breeding

range. However, if these fluctuations are indeed related to local and

regional weather conditions, then suitable habitat would need to be

provided throughout the breeding range to accommodate locally

variable precipitation and habitat conditions in any particular year.

These dynamics could make it difficult to designate and preserve

suitable habitat because Cassin's Sparrows may not be found in large

numbers on a particular site every year, except in the core of its range

in eastern New Mexico and western Texas.

Long term conservation of Cassin's Sparrows is linked to conservation of arid

grassland ecosystems, on both their breeding and wintering ranges. The limited

information available regarding Cassin's Sparrow response to various habitat

management regimes makes it difficult to recommend broad conservation

actions. However, some general recommendations can be made, based on

what we know, to help direct research to provide additional information.

l In the southwest portion of their range (southeastern Arizona

and southwestern New Mexico), where there is evidence that

heavy grazing can have detrimental effects on Cassin's

Sparrow habitat, removing cattle or at least reducing grazing

pressure will promote the preferred combination of shrub and

grass structure on Cassin's Sparrow habitat. Even

throughout the rest of its range, we do know that management

of rangeland to maintain a cover of grass underneath a shrub

layer that has not become too thick is crucial for Cassin's

Sparrow habitat needs.

Assessment Recommendation
40 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

l Woody encroachment across many southwestern grasslands has mixed

implications for Cassin's Sparrows. Where the shrub joined pure

grasslands, but have not become too dense, it may have resulted in

increased Cassin's Sparrow habitat. However, if the shrubs are of the

wrong species (e.g., juniper), or they become too dense, they are not

suitable Cassin's Sparrow habitat. In addition, range managers have

responded to woody encroachment with extensive shrub control

activities, which have the potential to negatively affect Cassin's

Sparrows. In areas where shrub removal is a major range improvement

activity, avoidance of methods that completely eliminate shrubs, and

focus on rehabilitation methods that create a native grass cover with at

least a minimal native shrub component would be beneficial.

l In areas where continuation of potentially negative

management activities is inevitable, focus on minimizing the

impact (e.g., reducing grazing pressure) and cooperating with

the landowners to conduct research to document the actual

effects of the practices on Cassin's Sparrows.

In light of the lack of information about Cassin's Sparrow ecology,

status, and response to management activities, perhaps the best

conservation action is support of additional research and monitoring

that will provide us with the information necessary to conserve this

species and its habitat.

Research Priorities l An initiative to survey potential Mexican habitat for Cassin's Sparrows

is warranted due to the lack of knowledge of its breeding and wintering

distributions and population status in Mexico. The habitat use research

needs described below also would benefit from comparative studies in

Mexico.

l Much of Cassin's Sparrow habitat throughout its range is grazed, and

because there is evidence that they are sensitive to the effects of

grazing on their habitat structure and composition in the southwestern

edge of their range, studies to document the effects of grazing and

other range management activities on Cassin's Sparrow habitat in the

core of their range (e.g., New Mexico and Texas) would be valuable.

l Ongoing shrub control and suburban development are also potential

factors affecting Cassin's Sparrows; efforts to take advantage of

opportunities to work with ranchers and developers to test the effect of

their activities on Cassin's Sparrows should be encouraged.

l Because there is evidence that Cassin's Sparrows are declining in the

Edwards Plateau and the South Texas Brushlands, efforts to study

Cassin's Sparrows there should be focused on identifying patterns of

habitat change or other factors associated with Cassin's Sparrow

declines.

l Because the Conservation Reserve Program (CRP) is one of the few

opportunities offering the possibility for creating additional bird

Conservation
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 41

habitat, studies of the effects of different CRP plantings on Cassin's

Sparrows would be valuable. A design focusing on comparisons of

different plantings, possibly including more "natural" grass/shrublands,

rather than comparisons with croplands, would be most productive.

l A suggestion has been made that habitat management activities aimed

at promoting the recovery of the Lesser Prairie-Chicken

(Tympanuchus pallidicinctus) would also benefit Cassin's Sparrows

where their ranges overlap (B. Busby pers. commun.). A study to

document the effects of these activities would be valuable.

l Little is known about Cassin's Sparrow reproductive biology, especially

productivity data. Of special interest would be studies comparing

reproductive success in different habitats. Cassin's Sparrows are

observed singing and displaying in a variety of habitats, but little is

known about whether productivity differs at these sites.

l Much of the information about Cassin's Sparrow habitat preferences

has been extracted from broad studies of avian habitat use or studies

focused on other questions. Quantitative studies specifically focused on

the habitat preferences (vegetative structure and composition, etc.) of

Cassin's Sparrows at the local (nesting and territory sites), habitat, and

landscape level in the core of its range would be valuable.

l Cassin's Sparrows are regularly described as responding to

precipitation, but few data are available to document these responses.

A range-wide study of Cassin's Sparrow over a number of years that

included recording of year-round precipitation data and associated

vegetation and prey availability fluctuations would be helpful in

confirming some of the hypotheses described in this report.

Conservation
42 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

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Fish Department, Nongame Branch, Phoenix, AZ.

Arnold, K. A. and K. L. P. Benson, Eds. Unpublished Data. The Atlas of

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Baicich, P. J. and C. J. O. Harrison. 1997. A guide to the nests, eggs, and

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Baumgartner, F. M. and A. M. Baumgartner. 1992. Oklahoma bird life.

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vegetation to burning sacaton grasslands in southeastern Arizona.

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Bock, C. E., J. H. Bock, K. L. Jepson, and J. C. Ortega. 1986. Ecological

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in a semidesert grassland site. Journal of Range Management

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Bock, C. E. and B. Webb. 1984. Birds as grazing indicator species in

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50 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 51

Appendix A - State Summaries

APPENDIX A

STATE SUMARIES In conducting this status assessment, information was solicited from

throughout the range of the Cassin’s Sparrow, with requests for

information going to contacts in eight states and Mexico. The state

summaries (summary for Mexico is included) which follow summarize

the responses received. The following information is included, if

available: state distribution summary, BBS summary, CBC summary,

BBA summary, state research and monitoring efforts, known “major”

breeding populations in the state, state legal status, Natural Heritage

Program state rank, a brief description of habitat conditions, and a brief

description of threats.

The Natural S1 = Critically imperiled or extremely rare in the state;

Heritage Program generally five or fewer occurrences.

State Ranks Defined S2 = Imperiled or very rare in the state;

generally six to 20 occurrences.

S3 = Rare, uncommon, or found in a restricted range in the state;

21 to 100 occurrences.

S4 = Common and apparently secure in the state.

S5 = Common and demonstrably secure in the state.

Some states utilize ranks followed by a “B”, e.g., S4B, to indicate the

rank applies only to the status of breeding occurrences. Ranks followed

by an “N” refer to nonbreeding status, and ranks followed by an “M”

refer to migration status.
52 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

UNITED STATES

ARIZONA Cassin’s Sparrows are found in southeastern Arizona grasslands east

Summary of the Baboquivari Mountains in Pima County to the New Mexico

border, and south from the Mogollon Rim and the Salt River to the

Mexican border (including Santa Cruz, Cochise, and Graham Counties)

(Monson and Phillips 1981; Phillips et al. 1964; Latta et al. 1999). In

Arizona, Cassin’s Sparrows occur in grassland mixed with acacias

(Acacia sp.), ocotillo, oaks, and mesquite (Flesch 1997; Rising 1996;

Ohmart 1966); they have also been observed in sacaton grasslands (D.

Krueper pers. commun.). The first documented nest in Arizona was

located in 1965 near Tucson (Ohmart 1966); Ohmart reported nesting

from late July to early September. Since then nests have been found 20

km northwest of Benson, south of Elgin, and west of the San Simon

Cienega near the New Mexico border (Monson and Phillips 1981).

There is a single, documented nest for Cassin’s Sparrow in late Aprilearly May in Cochise County, near Douglas, Arizona in 1995 (A.

Moorhouse written commun.). Breeding activity is reported from July

through September (Maurer et al. 1989; Monson and Phillips 1981;

Ohmart 1966). Cassin’s Sparrows also winter in southeastern Arizona,

with records from the Buenos Aires National Wildlife Refuge, Tucson,

AWRR, and the Chiricahua Mountains (Williams and LeSassier 1968;

C. Gordon pers. commun.)

BBS BBS trend data for the state of Arizona are of limited value since there

are insufficient routes (n = 5) for which sufficient, reliable data exist for

analysis. As a description of distribution within the state, BBS data

show Cassin’s Sparrow records from routes in Cochise, Santa Cruz,

Pima, Graham, Pinal, and Coconino Counties

(J. R. Sauer unpub. data a).

CBC For the years 1959-1988, CBC data show Cassin’s Sparrows recorded

on 18 CBC circles in Arizona. Those circles that show a mean relative

abundance per circle > 1.00 are Nogales (1.35), Atascosa Highlands

(1.00), Ramsey Canyon (2.36), Buenos Aires NWR (1.42), Elfrida (1.68),

and Portal (105.3 - due to one large count year) (J. R. Sauer unpub.

data b).

Atlas The Arizona Breeding Bird Atlas field data have been collected (1993 -

1998) and the atlas is currently in draft form with hopes of publication

in the near future. Atlas data (Arizona Breeding Bird Atlas unpub.

data) show that most possible/probable or confirmed breeding records

are located in Cochise, Pima, and Santa Cruz Counties, with a separate

cluster in Yavapai County, and individual records in Pinal and Greenlee

Counties (Figure 7 Atlas map). All confirmed breeding records for

which habitat information is available (four of six) recorded the habitat

as semidesert grassland. The majority of probable breeding records (20

of 27) were also recorded as semidesert grassland, with remaining

records in Chihuahuan desert scrub, Sonoran desert scrub, Sonoran

savannah grassland, and Sonoran riparian scrub.
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 53

Appendix A - State Summaries

Figure 7. Cassin’s Sparrow distribution in Arizona. Shown as blocks of possible/probable, and

confirmed breeding occurrence. Data gathered from 1993 - 1998 (Arizona Breeding

Bird Atlas unpub. data).

Research / Monitoring Carl and Jane Bock (University of Colorado) have conducted a

substantial amount of research on grassland bird communities in

southeastern Arizona, focusing on lands within and surrounding the

Appleton-Whittell Research Ranch (AWRR) (Bock and Bock 1992,

1988, 1978; Bock and Webb 1984; Bock et al. 1992; Bock et al. 1986; Bock

et al. 1984). Many of these manuscripts include information on Cassin’s

Sparrows described elsewhere in this document. They continue to be

involved in research in this area, for example, recently having proposed

research regarding the effects of suburban growth on grassland bird

communities in the Sonoita Valley.

Brian Maurer conducted several studies of the bird communities on the

Santa Rita Experimental Range (SRER) (Maurer 1986, 1985; Maurer

et al. 1989) that included information about Cassin’s Sparrows

described elsewhere in this document.
54 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

A monitoring program to document the distribution and abundance of breeding

birds on the Buenos Aires National Wildlife Refuge was initiated with a pilot

project in 1996, and two years of data collection in 1997 and 1998. This resulted

in a report (Flesch 1997) which describes Cassin’s Sparrow as the most

abundant bird detected during the point counts. In 1997, he counted a total of

207 Cassin’s Sparrows at a series of 100 m limited distance point counts and

553 during unbounded counts, with a maximum of five individuals found at a

single station. In 1998, Cassin’s Sparrows were significantly more abundant

than in 1997, with a total of 336 detected within 100 m and 919 recorded for

unbounded counts (A. Flesch written commun.). Using the 100 m limited

distance point counts from 1998, Flesch calculated a density of 86 singing males

per 40 ha. Making the assumptions that every singing male represented a mated

pair, and that the survey points provide a representative sample of the grassland

on the refuge, he calculated that the 46,500 ha of grassland on Buenos Aires

NWR could support approximately 100,000 pairs of Cassin’s Sparrows in a

good year. He did note that this may be an overestimate since some singing

males might not be paired. He also reported observing birds carrying food and

fecal sacs during the survey period. Buenos Aires NWR expects to continue

this monitoring program.

Caleb Gordon, a doctoral student at the University of Arizona, has

conducted five years of research on the wintering site fidelity of

grassland birds on the Buenos Aires NWR and at the AWRR (Gordon

In Press a and b). Cassin’s Sparrows are among the species he has mistnetted at both sites. He has documented the wide fluctuations in

Cassin’s Sparrow densities on the Buenos Aires NWR between years.

Nine Cassin’s Sparrows were captured in the winter of 1997 and, with

the same amount of effort (nine capture days), 43 were captured in the

winter of 1998. Although 23 Cassin’s Sparrows were captured on only

three capture days in the winter of 1999, by extrapolating along the

accumulation curve from previous years, he estimates that approximately 35 birds would have been captured with nine days of effort.

Additional results from this work have been presented elsewhere in

this document. Gordon also conducted two Breeding Bird Census plots

on the Buenos Aires NWR, one of which supported a number of

Cassin’s Sparrows.

The BLM has conducted various bird surveys on their land in

southeastern Arizona, including the San Pedro Riparian National

Conservation Area (1986 - 1991; some begun again in 1998) and the

Empire Cienega Resource Conservation Area (1992-1996), both of

which have recorded Cassin’s Sparrows. In the sacaton-mesquite

grasslands along the San Pedro RNCA, one transect showed annual

peak densities (based on Emlen transects) during the breeding season

(July, August and September) of 41, 66, 91, and 19 birds/40 ha in

respective years; a second transect showed annual peak densities of 39,

26, and 14 birds/40 ha (D. Krueper written commun.). See Grazing

section above for additional information about effects of grazing on

Cassin’s Sparrows at this site.

Janet Ruth, a research biologist for the USGS Midcontinent Ecological Science
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 55

Appendix A - State Summaries

Center, initiated a new study on the vegetative structure and composition of

habitat used by wintering grassland birds in southeast-ern Arizona in the winter

of 1998-1999. She has worked in collaboration with Caleb Gordon (University

of Arizona) and is conducting research on public and privately-owned grassland

sites in the Sonoita Valley, the San Rafael Valley, and on the Buenos Aires

NWR. Data on Cassin’s Sparrows has already been collected at several of

these sites and the project is scheduled to continue through the winter of 2000-

2001.

Major Populations The Buenos Aires NWR may support the largest population of

breeding Cassin’s Sparrows in Arizona (A. Flesch pers. commun.).

State Status None (T. Corman pers. commun.).

Natural Heritage Rank State rank - S4 (S. Schwarz pers. commun.).

Habitat Condition Bahre (1995) provides the most comprehensive description of the

historic changes that have occurred in the grasslands of southeastern

Arizona, roughly comparable with the Cassin’s Sparrow distribution in

the state. He noted that the two most dramatic changes were the

extensive increases in woody shrubs and trees within the grasslands,

and landscape fragmentation resulting from urban and rural settlements. Parker and Martin (1952) are cited for their report that by 1952,

fully half of the 3.8 million ha supporting mesquite in southern Arizona

had been colonized by that species since 1850. It would be difficult to

determine whether this represents increased or decreased Cassin’s

Sparrow habitat since their habitat preferences seem to be related to

the relative density of shrubs and grass cover. Bahre also reports that

thousands of ha of grassland were cleared for irrigated agriculture in

the 1940’s with the developed capability to tap groundwater, but that it

has declined substantially since the 1970’s for many reasons,

unfortunately it has rarely reverted to native grasses. The Arizona

Partners in Flight Bird Conservation Plan (Latta et al. 1999) indicates

that semidesert grasslands, the primary habitat of Cassin’s Sparrows in

Arizona, were the most extensive grassland type in the state and

suffered the greatest historical acreage loss. They also add heavy and

over-grazing to the list of major impacts on this habitat type.

Threats In the arid grasslands of southeastern Arizona there is sufficient

information to say that heavy grazing poses an important threat to

Cassin’s Sparrow habitat (Bock and Bock 1988; Bock and Webb 1984)

(see detailed discussion about effects of grazing in the Management

section). In addition, encroachment of suburban development poses a

threat in areas like the Sonoita Valley (C. Bock pers. commun.).

Literature Cited Arizona Breeding Bird Atlas. Unpublished data (1993-1998). Arizona Game &

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56 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

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Maurer, B. A. 1986. Predicting habitat quality for grassland birds using

density-habitat correlations. Journal of Wildlife Management

50(4): 556-566.

Maurer, B. A. 1985. Avian community dynamics in desert grasslands:

observational scale and hierarchical structure. Ecological
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 57

Appendix A - State Summaries

Monographs 55(3): 295-312.

Maurer, B. A., E. A. Webb, and R. K. Bowers. 1989. Nest characteristics

& nestling development of Cassin’s and Botteri’s Sparrows in

southeastern Arizona. Condor 91: 736-738.

Monson, G. and A. R. Phillips. 1981. Annotated Checklist of the Birds of

Arizona. University of Arizona Press, Tucson, AZ.

Ohmart, R. D. 1966. Breeding record of the Cassin’s Sparrow in Arizona.

Condor 68(4): 400.

Parker, K. W. and S. C. Martin. 1952. The mesquite problem on southern

Arizona ranges. USDA Circular 908.

Phillips, A., J. Marshall, & G. Monson. 1964. The birds of Arizona.

University of Arizona Press, Tucson, AZ.

Rising, J. D. 1996. A guide to the identification & natural history of the

sparrows of the United States and Canada. Academic Press, New

York, NY.

Sauer, J. R. Unpub. data a. North American Breeding Bird Survey

results & analysis. Patuxent Wildlife Research Center, Laurel, MD.

Sauer, J. R. Unpub. data b. Christmas Bird Count results. Patuxent

Wildlife Research Center, Laurel, MD.

Williams, F. C. and A. L. LeSassier. 1968. Cassin’s Sparrow. Pages

981 - 990 in Life histories of North American cardinals, grosbeaks,

buntings, towhees, finches, sparrows, & allies (O. L. Austin, Jr.,

Ed.). Dover Publications, New York, NY.
58 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

NEW MEXICO

Summary Southern and eastern New Mexico lie within the core of Cassin’s Sparrow

breeding range. There have not been any comprehensive summaries of New

Mexico’s birds in the last 20 years, so many of the older accounts may no

longer be accurate (S. Williams pers. commun.). A map in Hubbard’s (1977)

article (Figure 8) on the status of this species shows records of birds ranging

from the northeast (Union County) to the southeast (Lea County) to the

southwest (Hidalgo and Grant Counties) and south of a diagonal line across the

state (including Sierra, Socorro, Bernalillo, Santa Fe, and San Miguel Counties).

Hubbard (1977) suggests, based on the lack of historical evidence prior to 1960,

that Cassin’s Sparrow has undergone a change in summer distribution and

breeding status, increasing in the southwestern parts of New Mexico over the

last decade or so (1960 to 1977). Cassin’s Sparrow is “only a rare, casual to

occasional winter resident in the state, credibly recorded in the south near

Carlsbad and Rodeo,” with most birds leaving the state by late September

(Hubbard 1977). S. Williams (pers. commun.) agreed that most breeding

Cassin’s Sparrows leave the state in winter but that some unknown number use

the southern tier of counties.

Bailey (1928) stated that Cassin’s Sparrows were most numerous in

shortgrass habitat interspersed with small shrubs, mesquite plains in

yucca patches, and barren hillsides with cacti, but that they also ranged

up into the foothills of Mount Capitan to the lower edge of the juniper

belt at about 5,500 feet. Other studies in New Mexico have documented

Cassin’s Sparrows breeding in alkali sacaton grasslands along the Pecos

River (Hildebrandt and Ohmart 1982), in mesquite-perennial

composites and mesquite-grasslands in the southwestern part of the

state (Wolf 1977), in mesquite-grasslands and creosote bush habitats in

southeastern New Mexico (Ligon et al. 1981), in grasslands with

saltbush in northeastern New Mexico (Mehlman 1995), and mesa

grassland, black grama grasslands, and creosote shrublands in southern

New Mexico (A. Pidgeon written commun.).

Hubbard (1977) states that Cassin’s Sparrows return in numbers and

begin singing in New Mexico by April and possibly in March. A.

Pidgeon (written commun.) records Cassin’s Sparrows during her point

counts at Fort Bliss in late May, although record numbers of Cassin’s

Sparrows arrived there in early May (May 5 - 12) in 1997. She suggests

that this earlier arrival was in response to the end of a drought lasting

several years. Hubbard (1977) reports that many or most Cassin’s

Sparrows leave their New Mexico range by late September.

Hubbard (1977) reports only three records of Cassin’s Sparrow nests in

New Mexico – one in San Miguel County in 1933 (Phillips 1944), and

two in Lea County in 1968. He reports these nest records from 16

June, 17 June, and 3 July. Surveys of breeding birds on the Kiowa/Rita

Blanca National Grasslands at Perico Creek in northeast New Mexico

have reported two nests – one found on 27 June 1991 and one on 24

June 1993, each containing 3-4 eggs (Schwarz 1995).

Ligon et al. (1981) report two nests from Lea and Eddy Counties on June 2 and

July 18 of 1979. A. Pidgeon (written commun.) reports ten nests from Fort
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 59

Appendix A - State Summaries

Bliss from June 2 - 21 during the years of 1996 - 1998.

Figure 8. Historical records of Cassin’s Sparrows in New Mexico.

Large black dots (l) represent locations cited in text.

BBS There are no significant patterns in Cassin’s Sparrow numbers in New

Mexico (Table 3) for either the entire time period of available BBS data

(1966 - 1996), or for either the 1966 - 1979 or 1980 - 1996 time periods

(Sauer et al. 1997).

In New Mexico, which is in the core of the Cassin’s Sparrow’s range,

there are no significant or consistent population trends over time,

either statewide or in any of the physiographic strata within the state. For

purposes of defining the distribution of Cassin’s Sparrows, most of the routes in
60 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

the southern half of the state recorded Cassin’s Sparrows; most of the routes in

the eastern one third of the state recorded them, and there are a number of

routes scattered throughout the rest of the state that have recorded them.

However, the routes showing consistent, large numbers of Cassin’s Sparrows

were all in the eastern one third of the state (J. R. Sauer unpub. data a).

Looking at the individual route records also gave an indication of areas where

numbers were consistently high year after year, and other areas where the

numbers varied substantially from year to year. Following are several

examples. A route in De Baca County commonly recorded 120 - 160

Cassin’s Sparrows and had a maximum year count of 244; a route in

Chaves County commonly recorded 50 - 100 with a maximum of 257; a

route in Roosevelt Co. showed 30 - 50 in some years, 120 - 130 in other

years, and a maximum of 251; and a route in San Miguel County showed

several years above 115 and one year with 9!

CBC For the years 1959 - 1988, CBC data show that Cassin’s Sparrows were

recorded on five CBC circles in New Mexico, but they are very scarce,

with a mean relative abundance per circle not exceeding 0.6. The

locations were Peloncillo Mountains, Carlsbad Caverns NP, Loving,

Las Cruces, and Caballo (J. R. Sauer unpub. data b).

Atlas There is not a Breeding Bird Atlas project in New Mexico.

Research / Monitoring Various surveys for breeding birds are being conducted as part of the

development of an Environmental Impact Statement for the McGregor

Range of Fort Bliss in Otero County, New Mexico (U.S. Army 1998;

A. Pidgeon written commun.). These data indicate that certain desert

shrubland and grassland habitats on Fort Bliss support significant

numbers of Cassin’s Sparrows in some years. These data use point

counts to document bird detections in seven different habitat types

(six study plots per habitat type). In years with more rain, like 1997

(B. Locke pers. commun.), the following habitat types supported

substantial numbers of Cassin’s Sparrows – creosote shrubland

(1996 - 17; 1997 - 203); mesa grassland (1996 - 22; 1997 - 93); and black

grama grassland (1996 - 3; 1997 - 193) (A. Pidgeon written commun.).

Mesquite shrublands did not support any Cassin’s Sparrows; sandsage

(Artemesia filifolia) shrublands (1996 - 2; 1997 - 3) and pinyon pine/

juniper (1996- 0; 1997 - 1) supported very few; and Viscid acacia

supported a moderate number in one year (1996 - 0; 1997 - 22).

B. Locke (written commun.) reported that the reason that mesquite

shrublands and sandsage shrublands did not support Cassin’s in this

location was because there is very little grass cover due to the sandy

soils; in comparison, the creosote shrublands supported an understory

of grama grasses. Intensive nest searching was also conducted as part

of this project, but the timing (mid-April to the end of June) does not

coincide well with the timing of Cassin’s Sparrow nesting. However,

some information regarding timing, size, and placements of nests was

available (A. Pidgeon written commun.) - see Breeding Ecology section.

She did note that Cassin’s Sparrows were present in late spring-early summer

because they did get Cassin’s Sparrows on the point counts (see above) which

are done in May. She also noted that in 1998, they were in the field until the
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 61

Appendix A - State Summaries

end of July and that, although Cassin’s Sparrows were present in the abovementioned habitat types earlier, they did not find any Cassin’s nests until after

the rains began in the middle of June.

A series of transect surveys conducted during the winter (1996) at Fort

Bliss, primarily to document distribution of Baird’s Sparrow comparing

upland and swale grassland habitats, also documented Cassin’s

Sparrow presence during the winter (U.S. Army 1998). Cassin’s

Sparrows were only found in the swale habitat and the rate of

detections/survey (n = 24) was 1.25.

A series of point count surveys were conducted in the summer of 1995

to compare the bird community at the Maxwell National Wildlife

Refuge (Colfax County, New Mexico) with the surrounding region

(Mehlman 1995). Cassin’s Sparrows were found in low numbers both

on the refuge and in the surrounding region (2 - 18 individuals per

survey), with somewhat larger numbers found during the point count

surveys in the surrounding region. They were consistently found in

grassland habitat with a saltbush component.

A number of “BBS-type surveys” of breeding birds have been

conducted annually on the Kiowa/Rita Blanca National Grasslands in

northeast New Mexico during the 1990’s (Schwarz, 1991 - 1997). The

survey conducted at Perico Creek regularly recorded 27 to 35

individuals. Schwarz recorded several nest records (see above). In

addition, the Colorado Bird Observatory, under contract by the U.S.

Forest Service, is conducting an inventory on the Kiowa/Rita Blanca

National Grasslands in 1999, using the area search protocol (M. Carter

pers. commun.).

The Bureau of Land Management (C. Alford pers. commun.) has

contracted for some grassland bird work involving vegetation/habitat

use of grassland birds. However, efforts to contact the contractor

through BLM were not successful.

Julie Meents conducted research for her dissertation on “Avian

Community Structure in Chihuahuan Desert Grasslands” for New

Mexico State University (Meents 1979) at sites in southern New

Mexico (Otero Mesa; Nutt; and Cloverdale) and northern Chihuahua,

Mexico (La Campana). Although she focused primarily on broader

measures of the total bird community (species diversity, species

dominance, density, standing crop biomass, and body size class), she

does provide information about average census numbers for Cassin’s

Sparrows at each site. Along 7.2 km roadside censuses, 14.5 Cassin’s

Sparrows were recorded in summer at Otero Mesa, 17.4 in summer at

Nutt, 8.0 in summer at Cloverdale, and 74.0 in summer and 1.0 in

winter at La Campana.

Christopher Rustay with Hawks Aloft is conducting some “BBS-type”

surveys of grassland birds in New Mexico (northwestern quadrant of

the state) in association with his work on Ferruginous Hawks, under

contract with BLM and other sources of funding. He did record some
62 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

Cassin’s Sparrows. Interestingly, he did observe several Cassin’s Sparrows in

southern San Juan County, the very northwestern part of the state (C. Rustay

pers. commun.).

From 1975 through 1981 the species composition and densities of the

bird community on the Los Medaños Waste Isolation Pilot Plant

(WIPP) in southeastern New Mexico (Eddy and Lea Counties) were

studied (Ligon et al. 1981). Of the four major habitat types studied

during 1978 to 1981, Cassin’s Sparrows were found regularly in

mesquite-grasslands and creosote bush habitats, showed up minimally

one year in mesquite-shinnery oak, and were not found in hummockmesquite habitat. Using Emlen transects to estimate density of

individuals per square km, Cassin’s Sparrows were found at densities

of 2.0, 64.0, 35.4, and 5.1 in respective years in mesquite-grassland

habitats, and at densities of 71.0, 82.9, 56.0, and 81.6 in creosote bush

habitats. Cole and Ligon (1978) suggest that heavy rainfall during fall/

winter/spring of 1978-79 may have resulted in a demonstration of the

upper limit to normal year-to-year variation in bird densities and

reproductive success. Vegetation analyses for that time period showed

a substantial increase in grass and forb cover and a sharp decrease in

bare ground. A 25-mile roadside census conducted twice monthly from

October 1978 - September 1979 showed that end of May through early

September was the peak time for observing Cassin’s Sparrows,

recording a range of 11 to 36 individuals along the route (Cole and

Ligon 1978). Two Cassin’s Sparrow nests were found and monitored

during the summer of 1979, each hatching and fledging three young.

During Baird’s Sparrow surveys conducted on Otero Mesa, singing

male Cassin’s Sparrows were observed in April of 1996 and 1999. In

addition, during the winter Cassin’s Sparrows were detected at

densities of 1.25/km, 0.04/km, and 0.4/km respectively during the

winters of 1996/97, 1997/98, and 1998/99 (R. Meyer pers. commun.).

Major Populations New Mexico clearly supports a large portion of the breeding population

of Cassin’s Sparrows, but insufficient information exists to identify

specific areas within the state that support major populations.

State Status None (S. Williams pers. commun.). There is some consensus among

experts in New Mexico that there, in the core of its range, populations

are stable, and it is one of the most abundant breeding birds (S.

Williams pers. commun.; H. Schwarz pers. commun.).

Natural Heritage Rank State rank - S5B/S5N (M. Altenbach pers. commun.).

Habitat Condition Historically, since European settlement, grassland vegetation types in

New Mexico have diminished greatly. During the last 150 years this

has resulted primarily in an increase in desert scrubland. In addition,

the transition desert grassland type now occupies areas previously occupied by

Mesa-Plains grasslands. There has also been an extensive advance of juniper

savannah, at the expense of grassland types. These changes have been

attributed to the impacts of grazing, farming, and modification of fire frequencies
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 63

Appendix A - State Summaries

(Dick-Peddie et al. 1993). They state that these “successional” trends were set

in motion early in the 20th century and predict that subsequent range

management efforts are unlikely to halt, let alone reverse the trends. Therefore,

they project continuing transformation of Mesa-Plains grassland to juniper

savannah and desert grassland, and transformation of much of the desert

grasslands to desert scrubland. There was very little documentation available

regarding the specific condition of Cassin’s Sparrow habitat in New Mexico. It

seems possible that the transformation of grasslands (defined by Dick-Peddie et

al. 1993 as supporting very low shrub density) to desert grasslands (which have

a larger shrub component) may have been beneficial to Cassin’s Sparrows.

This may help explain the lack of significant declines in Cassin’s Sparrow

numbers demonstrated by the BBS. However, the further transformation of

desert grasslands to desert scrubland will be less beneficial, as these habitats

support much less grass cover and a much denser shrub component.

Threats There was very little information available about the particular threats

that face Cassin’s Sparrows in New Mexico. However, as mentioned

above, transformation of desert grasslands to desert scrubland may

pose threats to Cassin’s Sparrow habitats. In addition, as treated

elsewhere in this document, shrub control efforts initiated in response

to woody encroachment pose an additional threat to the species.

Literature Cited Bailey, F. M. 1928. Birds of New Mexico. New Mexico Department of

Game and Fish, Albuquerque, NM.

Cole, D. C. and J. D. Ligon. 1978. Densities and species composition of

the avifauna of the Los Medaños WIPP Site, southeastern New

Mexico. Chapter 10 in Annual report of biological investigations at

the Los Medaños Waste Isolation Pilot Plant area of New Mexico

for FY 1978 (T. L. Best and D. W. Jackson, Eds.). Submitted to

Sandia Laboratories.

Dick-Peddie, W. A., W. H. Moir, & R. Spellenberg. 1993. New Mexico

vegetation: past, present and future. University of New Mexico

Press, Albuquerque, NM.

Hildebrandt, T. D. and R. D. Ohmart. 1982. Biological resource inventory

(vegetation and wildlife) - Pecos River Basin, New Mexico & Texas.

Final report to U.S. Bureau of Reclamation, Amarillo, TX.

Hubbard, J. P. 1977. The status of Cassin’s Sparrow in New Mexico and

adjacent states. American Birds 31(5): 933-941.

Ligon, J. D., J. Haydock, and J. C. Bednarz. 1981. Avifauna baseline studies at

the Los Medaños WIPP site, southeastern New Mexico. Report.

University of New Mexico, Albuquerque, NM.

Meents, J. K. 1979. Avian community structure in Chihuahuan desert

grasslands. Ph.D. dissertation. New Mexico State University, Las

Cruces, NM.
64 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

Mehlman, D. W. 1995. A survey of grassland bird species of the Maxwell

National Wildlife Refuge. Report contracted by USFWS, Maxwell NWR.

Phillips, A. R. 1944. Status of Cassin’s Sparrow in Arizona. Auk

61: 409-412.

Sauer, J. R. Unpub. data a. North American Breeding Bird Survey

results & analysis. Patuxent Wildlife Research Center, Laurel, MD.

Sauer, J. R. Unpub. data b. Christmas Bird Count results. Patuxent

Wildlife Research Center, Laurel, MD.

Sauer, J. R., J. E. Hines, G. Gough, I. Thomas, & B. G. Peterjohn. 1997.

The North American Breeding Bird Survey results & analysis.

Version 96.4. Patuxent Wildlife Research Center, Laurel, MD.

Schwarz, H. R. 1997. Cibola National Forest breeding bird survey report

for 1997. USDA Forest Service.

 .1996. Cibola National Forest breeding bird survey report

for 1996. USDA Forest Service.

 .1995. Cibola National Forest breeding bird survey report

for 1995. USDA Forest Service.

 .1993. Cibola National Forest breeding bird survey report

for 1993. USDA Forest Service.

 .1991. National Grasslands Breeding Bird Report - Cibola

National Forest. USDA Forest Service.

U.S. Army. 1998. 1996-97 post-wide survey of federally listed & other

species of concern at Fort Bliss. Report prepared by TRC Mariah

Associates, Inc.

Wolf, L. L. 1977. Species relationships in the avian genus Aimophila.

Ornithological Monographs Number 23. American Ornithologists’

Union, Baltimore, MD.
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 65

Appendix A - State Summaries

TEXAS

Summary The Cassin’s Sparrow is a common to fairly common breeder in the western

two-thirds of Texas (Oberholser 1974) - a major part, with New Mexico, of the

core of their range. Oberholser reports that breeding birds were collected north

to Potter and Lipscomb, east to Dallas, south to Cameron, and west to El Paso

Counties. His map (Oberholser 1974) is very similar to the more recent map

provided by the Texas Breeding Bird Atlas project (see below). Seyffert

(1985) also describes Cassin’s Sparrow as an uncommon to common summer

resident throughout the Texas Panhandle counties.

The breeding season in Texas goes from early March to early August

(Oberholser 1974). In Texas, Cassin’s Sparrows occur in several habitat

types. They inhabit shortgrass plains, chiefly where scattered low

mesquites, cacti, yucca, or oaks occur. In the Texas Panhandle, they

have been observed in playa lake basins (Fischer et al. 1982), they

reportedly thrive in lush, open grasslands with occasional low bushes or

sunflowers (Oberholser 1974), and along the southern Texas coast they

are found in tall bunchgrass (Oberholser 1974). Williams and LeSassier

(1968) also mention several references to Cassin’s Sparrow found in or

near mountainous regions - treeless, grassy plains with scattered yucca

on the southern slopes of the Davis Mountains in the Trans-Pecos,

Texas (5,000+ feet); open meadows with surrounding oaks in the Davis

Mountains; and on the mesa that surrounds the Chisos Mountains

(4,000 feet); etc.

Eggs are reported from March 1 through August 1 (Oberholser 1974);

Williams and LeSassier (1968) report egg dates from April 12 to July

23. The Texas Breeding Bird Atlas project (Arnold and Benson unpub.

data) reports nesting activity from early May to late June.

In winter, Cassin’s Sparrows withdraw south, occurring only in

western and south-central parts of the state, north to about the 33rd

parallel (Oberholser 1974; Williams and LeSassier 1968). Oberholser

reports that wintering birds were taken northwest to Culberson and

Brewster, east to Bexar and Nueces, and south to Cameron Counties.

The Checklist of the Birds of Texas (Texas Ornithological Society 1995)

describes it as an uncommon winter resident from El Paso County, the

Edwards Plateau, and south through the South Texas Plains. Bryan

(pers. commun.) stated that Cassin’s Sparrows used a more limited set

of habitat types in the winter than they did while breeding. He felt

they were using the thickest, most well-developed grassland with a

shrub mosaic, and although they were in the Trans-Pecos in the winter,

they weren’t using the desert scrub that they might use during

breeding season.

BBS For the entire time period of available BBS data (1966 - 1996), there

was a highly significant decline (P = 0.00; n = 99) of - 2.9 % per year for

Cassin’s Sparrows in Texas (Table 3). There were no significant

patterns for the state for either the 1966 - 1979 or 1980 - 1996 time

periods (Sauer et al. 1997). See the Population Trends section and

Table 3 for a breakout of trends in the Physiographic Strata that comprise
66 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

Texas and a discussion of their significance. Consistent with distributional

information elsewhere (although too numerous to list here by county), Cassin’s

Sparrows were recorded on almost every BBS route in the western 2/3 of the

state (J. R. Sauer unpub. data a).

Fig. 9. Cassin’s Sparrow distribution in Texas. Shown as blocks with possible, probable and

confirmed breeding occurences. Data gather from 1987 - 1992, from Arnold and Benson

(unpub. data).

CBC For the years 1959 - 1988, CBC data show that Cassin’s Sparrows were

recorded on 56 CBC circles in Texas. Those locations where the mean

relative abundance per circle > 1.0 were Laguna Atascosa NWR (1.4),

Falcon Dam SP (2.1), Zapata (8.9), Chisos Mountains (1.6), Del Norte

Mountains (2.1), Sheffield (1.3), Imperial (1.8), and Odessa (2.0) (J. R.

Sauer unpub. data b).
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 67

Appendix A - State Summaries

Atlas The Atlas of the Breeding Birds of Texas (Arnold and Benson unpub. data) is

currently in draft form with hopes of publication in the next year. The species

account states that Cassin’s Sparrows breed in the western part of Texas from

the Panhandle to the Gulf Coast, but in the winter are found only in the southern

part of the state. It goes on to say that project data (1987-1992) (Figure 9)

indicate that they breed from the High Plains and the Davis Mountains to the

Hill Country and the Coastal Prairies, and that nesting activities are recorded

from early March through August. The Texas Breeding Bird Atlas project did

not collect data regarding habitat type.

Research / Monitoring John Schnase conducted research for his Master’s Thesis on “The

breeding biology of Cassin’s Sparrow in Tom Green County, Texas” for

Angelo State University (Schnase 1984) at the Angelo State University

Management, Instruction and Research area. This information

provides the most extensive treatment available of Cassin’s Sparrow

ecology and behavior. His results (Schnase 1984; Schnase and Maxwell

1989; Schnase et al. 1991) are described throughout this report.

A study of landscape scale habitat relations for birds in Big Bend

National Park (W. Barrow pers. commun.) was conducted from 1995 to

1997 by Kevin Gutzwiller (Baylor University) and Wylie Barrow

(USGS National Wetlands Research Center). They conducted point

counts at 70 permanent plots at the park and measured 23 habitat

characteristics at a landscape scale (within 1 km and 2 km of the points)

using Geographic Information Systems (GIS). A manuscript analyzing

these data is expected during the winter of 1998-99. Although Cassin’s

Sparrows are sporadic in abundance at Big Bend in the spring (W.

Barrow pers. commun.), in 1997 they did record Cassin’s at 19 of their

points (in 1995 and 1996 they were recorded at two and six points

respectively), and hope to publish information about their association

with landscape features.

Berthelesen and Smith (1995) conducted a study of the value of

Conservation Reserve Program (CRP) lands to breeding nongame

birds in the Texas Southern High Plains (southern part of the

Panhandle) that provided some information about Cassin’s Sparrow

responses - see the Management section on CRP.

Maxwell (1979) conducted a study of the bird community in the Concho

Valley of west-central Texas for his dissertation. This included a

comparison of bird densities in eight different plant communities. See

more about his results in the Habitat section.

Emlen (1972) conducted one of the few studies of the size and structure

of wintering avian communities in seven habitat types in south Texas.

This included some information about Cassin’s Sparrows - see

Wintering Habitat section.

Major Populations Texas clearly supports a major portion of the total breeding population

of Cassin’s Sparrows. No information was available to describe

particular locations for major population centers within the state.
68 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

State Status None (D. Scott pers. commun.)

Natural Heritage Rank Former State rank - S4B. The Texas Natural Heritage Program no longer

exists, but the Texas Parks and Wildlife Department maintains the database.

Although Cassin’s Sparrows do winter in Texas, the database did not include a

nonbreeding state rank (D. Scott pers. commun.)

Habitat Condition Samson and Knopf (1994) report that Texas historically had 7,800,000

ha of shortgrass that has been reduced to 1,600,000 ha (decline of 80%), and

had 14,100,000 ha of mixed grass that has been reduced to 9,800,000 ha

(decline of 30%). It is difficult to know exactly how these categories compare

with Cassin’s Sparrow habitat in Texas, especially because desert shrub/

grasslands are not discussed in this reference and undoubtedly represent some

Cassin’s Sparrow habitat. However, it does provide an idea of the scope of

habitat change that occurred with the advent of European settlement in Texas.

Oberholser (1974) provides some comments about Cassin’s Sparrow

response to brush control efforts in Texas beginning in the 1930’s (see

below). Maxwell (1979), in his description of the history of Concho

Valley, Texas states that the 19th century grasslands have largely been

replaced by mesquite woodland and shrubland on deeper soil sites and

juniper savannah on thinner soil slopes. He noted that several species

that utilize brushy mesquite land in the 1970’s were also common in

1887, including Cassin’s Sparrows.

Threats In light of Cassin’s Sparrow requirements for a shrub component in

their habitat, programs to promote brush or shrub control to benefit

grazing have a potential to negatively impact this species. Oberholser

(1974) provides some observations about the history of brush control in

Texas. He suggests that Cassin’s Sparrow habitat has actually

increased since 1933 when the Soil Conservation Service began to

subsidize ranchers for brush control. By 1968 brush removal had been

attempted on much of this species’ range in the western two thirds of

Texas. In cases where clearing was followed by a growth of native

grasses and a sprouting of young mesquites and low bushes, he states

that Cassin’s Sparrows have benefitted. However, more extensive and

efficient mechanical and chemical means of extirpating all woody

vegetation have been developed (Oberholser 1974) and wide application

of these methods is posing new threats to this species. However, it

appears that the impacts are somewhat dependent on the history and

ecology of the particular habitat.

Edwards Plateau The Edwards Plateau of central and west-central

Texas has undergone significant landscape-level habitat changes in

recent history. Prior to settlement, most of the Plateau was a firemaintained savannah whose principal woody species was a live oak

(Quercus fusiformis). Due to intense, confined grazing which removes

fuel and reduces water infiltration rates, and the resulting decreased

fire frequency, the Plateau has experienced widespread expansion of

woody plants, especially Ashe juniper (Juniperus ashei), resulting in

dense stands locally known as “cedar brakes” (Fowler and Dunlap 1986;

Riskind and Diamond 1988; Taylor and Smeins 1994; Fuhlendorf et al. 1997).
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 69

Appendix A - State Summaries

The result is a transformation from grassland and oak savannah communities to

a woodland dominated by juniper, oak, and mesquite. In addition to the threats

posed by woody encroachment, there has been substantial suburban

development in the eastern and southern parts of the Edwards Plateau (B.

Ortego pers. commun.; K. Bryan pers. commun.), with the Plateau becoming

more important as a recreational and second home area (USFWS 1992;

Fuhlendorf et al. 1997). For more discussion of these issues and their implication

for Cassin’s Sparrows, see the Population Estimates and Trends section of this

document.

South Texas Brushlands In presettlement times, much of the South

Texas Brushlands was covered by grassland with scattered groves of

thorn forest, with densely forested low and riparian areas (Rappole et

al. 1986). However, as a result of a combination of fire reduction and

grazing pressures, by the early 1900’s there had been a considerable

change in the grasslands, with an increase in cacti and woody species on

upland sites, an increase in annual grasses, and a decrease in perennial

grasses (Rappole et al. 1986), so that south Texas is described now as

semiarid brushland. In comparison with the Edwards Plateau, in the

South Texas Brushlands, the threats posed to Cassin’s Sparrows may

actually be related to destruction of brushland through conversion to

agriculture, urban development, and brush control, as opposed to shrub

encroachment. For more discussion of these issues and their implication

for Cassin’s Sparrows, see the Population Estimates and Trends

section of this document.

Along the eastern coast of Texas, the occurrence of Cassin’s Sparrow is

limited by (1) conversion of native prairies to agriculture and other

uses, (2) excessive grazing on private property, and (3) insufficient

grazing in areas where grass forms dense layers up to 50 cm high,

which is not satisfactory habitat for Cassin’s Sparrows (B. Ortego pers.

commun.).

Literature Cited Arnold, K. A. and K. L. P. Benson, Eds. Unpublished Data. The Atlas of

the Breeding Birds of Texas. Texas Breeding Bird Atlas Project,

College Station, TX.

Berthelsen, P. S. and L. M. Smith. 1995. Nongame bird nesting on CRP

lands in the Texas southern high plains. Journal of Soil and Water

Conservation 50(6): 672-675.

Emlen, J. T. 1972. Size and structure of a wintering avian community in

southern Texas. Ecology 53(2): 317-329

Fischer, D. H., M. D. Schibler, R. J. Whyte, and E. G. Bolen. 1982.

Checklist of birds from the playa lakes of the southern Texas

panhandle. Bulletin of the Texas Ornithological Society 15: 2-7

Fowler, N. L. and D. W. Dunlap. 1986. Grassland vegetation of the eastern

Edwards Plateau. American Midland Naturalist 115(1): 146- 55.
70 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

Fuhlendorf, S. D., F. E. Smeins, and C. A. Taylor. 1997. Browsing & tree

size influences on Ashe juniper understory. Journal of Range

Management 50(5): 507-512.

Maxwell, T. C. 1979. Avifauna of the Concho Valley of west-central

Texas with special reference to historical change. Ph.D.

dissertation. Texas A & M University, College Station, TX.

Oberholser, H. C. 1974. The bird life of Texas. University of Texas Press,

Austin, TX.

Rappole, J. H., C. E. Russell, J. R. Norwine, and T.E. Fulbright. 1986.

Anthropogenic pressures on marginal, neotropical, semiarid

ecosystems: the case of south Texas. Science of the Total

Environment 55: 91-99.

Riskind, D. H. and D. D. Diamond. 1988. An introduction to

environments and vegetation. Pages 1-15 in Edwards Plateau

Vegetation: plant ecological studies in central Texas (B. B. Amos &

F. R. Gehlbach, Eds.). Baylor University Press: Waco, TX.

Samson, F. and F. Knopf. 1994. Prairie conservation in North America.

Bioscience 44(6): 418-421.

Sauer, J. R. Unpub. data a. North American Breeding Bird Survey

results and analysis. Patuxent Wildlife Research Center, Laurel,

MD.

Sauer, J. R. Unpub. data b. Christmas Bird Count results. Patuxent

Wildlife Research Center, Laurel, MD.

Sauer, J. R., J. E. Hines, G. Gough, I. Thomas, and B. G. Peterjohn. 1997.

The North American Breeding Bird Survey results and analysis.

Version 96.4. Patuxent Wildlife Research Center, Laurel, MD.

Schnase, J. L. 1984. The breeding biology of Cassin’s Sparrow in Tom

Green County, Texas. M.S. thesis. Angelo State University,

Angelo, TX.

Schnase, J. L., W. E. Grant, T. C. Maxwell, and J. J. Leggett. 1991. Time

and energy budgets of Cassin’s Sparrow during the breeding

season: evaluation through modelling. Ecological Modelling

55: 285-319.

Schnase, J. L. & T. C. Maxwell. 1989. Use of song patterns to identify

individual male Cassin’s Sparrows. Journal of Field Ornithology

60(1): 12-19.

Seyffert, K. D. 1985. The breeding birds of the Texas panhandle.

Bulletin of the Texas Ornithological Society 18:7-20.
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 71

Appendix A - State Summaries

Taylor, C. A. and F. E. Smeins. 1994. A history of land use of the

Edwards Plateau and its effect on the native vegetation. Pages 1-8

in Proceedings of Juniper Symposium (C. A. Taylor, Ed.).

Technical Report 94-2. Texas Agricultural Experimental Station,

College Station, TX.

Texas Ornithological Society. 1995. Checklist of the birds of Texas. Texas

Ornithological Society.

U.S. Fish and Wildlife Service. 1992. Golden-cheeked Warbler

(Dendroica chrysoparia ) recovery plan. Albuquerque, NM.

Williams, F. C. and A. L. LeSassier. 1968. Cassin’s Sparrow. Pages

981-990 in Life histories of North American cardinals, grosbeaks,

buntings, towhees, finches, sparrows, and allies (O. L. Austin, Jr.,

Ed.). Dover Publications, New York, NY.
72 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

OKLAHOMA Sutton (1967) describes Cassin’s Sparrows as transients and summer

Summary residents in western Oklahoma. It is described as regularly occurring in the

three panhandle counties (Cimarron, Texas, and Beaver Counties), as well as

the following western counties (Harper, Woodward, Ellis, Roger Mills, and

Beckham Counties) (M. Howery pers. commun.). Baumgartner and

Baumgartner (1992) note that Cassin’s Sparrows expand eastward in drought

years when normally tall or mixed grassland approximates the arid conditions

further west, and recede westward in wet years when the vegetation is too

lush. In these dry years they are found as far east as Alfalfa, Major, Blaine,

Canadian, Caddo, Comanche, and Tillman Counties (M. Howery pers.

commun.; J. Grzybowski pers. commun.). This is quite similar to Davis’s

(1963) and Sutton’s (1967) statements that they have been seen eastward to

Grant, Oklahoma, Cleveland, McClain, Caddo, Comanche, Jefferson, and Love

Counties, although their lines are drawn slightly further east in the state.

Sutton (1967) reports Cassin’s Sparrows as seen from March 24 to

November 21; Baumgartner and Baumgartner (1992) list it as seen

from late April through August with the above dates shown as

“outliers.” Sutton (1967) reports nest records for Woods, Cimarron,

Cleveland, and Texas Counties. Egg dates are from May 26 - July 22

(Johnsgard 1979; Sutton 1967).

In Oklahoma, lightly grazed sandy prairies with scattered sage, yucca,

cactus, mesquite, and shinnery oaks are preferred habitats (Johnsgard

1979; Sutton 1967); Baumgartner and Baumgartner (1992) list them as

present in the following grassland associations in western Oklahoma -

mixed-grass plains, shinnery oak-grassland, mesquite-grassland, and

shortgrass plains. M. Howery (written commun.) describes Cassin’s

Sparrows as one of the three most common species in the sandsage/

bluestem grasslands of northwestern Oklahoma. He also noted that

they are fairly common in shinnery oak/bluestem grasslands, found

locally in shortgrass prairie where yucca, cholla and/or sandsage are

present in the panhandle, and locally in mesquite/bluestem grasslands

in southwestern Oklahoma. In years when they are found in central

Oklahoma, they are usually in tallgrass prairie pastures.

BBS For the entire time period of available BBS data (1966 - 1996) there was

no significant pattern for Cassin’s Sparrow numbers in Oklahoma

(Table 3). For 1966 - 1979 there was a somewhat significant increase

(P = 0.20; n = 8) of +9.3% per year, and for 1980 - 1996 there was no

significant pattern (Sauer et al. 1997). To describe distribution in

Oklahoma, Cassin’s Sparrows were found on all BBS routes within

Cimarron, Texas, Beaver, Harper, Woods, Woodward, Roger Mills,

Dewey, Beckham, Harmon, Greer, Kiowa, and Cotton Counties and on

some routes in Grant, Caddo, and Stephens Counties. The routes

showing the largest, most consistent numbers of Cassin’s Sparrows

were all in the panhandle, commonly recording 25 - 70 birds but rarely

showing more than 100; a few western states showed consistent annual

numbers of 5 - 15, and other counties showed sporadic, individual

records (J. R. Sauer unpub. data a)
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 73

Appendix A - State Summaries

CBC N/A

Atlas The Sutton Avian Research Center has taken the lead on an Oklahoma

Breeding Bird Atlas project, and 1998 was the second year of field data

collection on this project. A preliminary map (Oklahoma Breeding Bird

Atlas unpub. data) produced after the first two years of field data collection

(Figure 10 ) indicates Cassin’s Sparrow detections that are quite consistent with

state distributions described above.

Research / Monitoring No references were found to research or monitoring projects, other

than BBS, that covered Cassin’s Sparrows in Oklahoma.

Major Populations M. Howery (written commun.) has observed large numbers (100+) of Cassin’s

Sparrows on the Cooper Wildlife Management Area (WMA) of Woodward

County, and the Ellis County WMA. He reports that they are also fairly

common on the Packsaddle WMA (Ellis County), the Black Kettle National

Grasslands (Roger Mills County), and the Sandy Sanders WMA (Beckham and

Greer Counties). Howery has also received reports that they are common on

Lake Optima National Wildlife Refuge (Texas County) and the Beaver River

WMA (Beaver County). Probably none of these references could be called

major populations of Cassin’s Sparrows when compared with populations in the

core of their range in Texas and New Mexico.

State Status None (M. Howery pers. commun.)

Natural Heritage Rank State ranks - S3B, S2M (M. Howery pers. commun.). The imperiled

migratory score is probably due to the fact that there are few Cassin’s

Sparrows migrating through Oklahoma.

Habitat Condition Samson and Knopf (1994) report that Oklahoma historically had

2,500,000 ha of mixed grass and 1,300,000 ha of shortgrass; however

they were unable to find any estimates of current coverage. Although,

these numbers are not directly comparable, and he did not have data

for shortgrass in Oklahoma, Knopf (1994) reports that for private land

in Oklahoma, 60,950 km2 of mixed grass remains as rangeland, while

46,820 km2 is in cropland and 28,890 km2 is in pasture-land, based on

USDA figures from 1987. Note that this does not include any public

lands in grassland in the state.

Insufficient information was available to make statements about the

specific condition of Cassin’s Sparrow habitat in Oklahoma.

Threats In the western part of the state, where Cassin’s Sparrows are found,

there is little suburban development, and much of the land remains in

rangeland, with little converted to irrigated cropland (M. Howery pers.

commun.). There is little information available about specific threats to

Cassin’s Sparrows or their habitat in Oklahoma.
74 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

Figure 10. Cassin’s Sparrow distribution in Oklahoma. This is based on the first two years (1997-1998) of data

collection of the five-year Oklahoma Breeding Bird Atlas project (Oklahoma Breeding Bird Atlas

unpub. data). Shown as blocks where Cassin’s Sparrows were present (includes possible, probable

and confirmed breeding occurrences).

Literature Cited Baumgartner, F. M. and A. M. Baumgartner. 1992. Oklahoma bird life.

University of Oklahoma Press, Norman, OK.

Davis, W. M. 1963. Eastward records of Cassin’s Sparrow in Oklahoma.

Southwestern Naturalist 8(1): 49-50.

Johnsgard, P. A. 1979. Birds of the great plains. University of Nebraska

Press, Lincoln, NE.

Knopf, F. L. 1994. Avian assemblages on altered grasslands. Studies in

Avian Biology Number 15.

Oklahoma Breeding Bird Atlas. Unpublished data. Sutton Avian

Research Center, Bartlesville, OK.

Samson, F. and F. L. Knopf. 1994. Prairie conservation in North

America. Bioscience 44(6): 418-421.

Sauer, J. R. Unpub. data a. North American Breeding Bird Survey

results and analysis. Patuxent Wildlife Research Center, Laurel,

MD.

Sauer, J. R., J. E. Hines, G. Gough, I. Thomas, and B. G. Peterjohn. 1997.

The North American Breeding Bird Survey results and analysis.

Version 96.4. Patuxent Wildlife Research Center, Laurel, MD.

Sutton, G.M. 1967. Oklahoma birds. University of Oklahoma Press,

Norman, OK.
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 75

Appendix A - State Summaries

COLORADO Cassin’s Sparrows are common to abundant summer residents in the

Summary southeastern plains of Colorado. They are regularly found in the

southeastern part of the state (from Las Animas, Huerfano, Pueblo,

and El Paso Counties east to the border) and irregularly into the

northeast (including portions of Kit Carson, Yuma, Washington, Sedgwick,

Logan, Washington, Morgan, and Weld Counties) (Andrews and Righter 1992;

Kingery 1998). They are considered accidental in the eastern foothills in

summer and winter (two records) (Andrews and Righter 1992).

Andrews and Righter (1992) and Rising (1996) state that Cassin’s

Sparrows are found primarily in rabbitbrush and sandsage grasslands

in Colorado. However, the Colorado Breeding Bird Atlas (Kingery

1998) found that nearly 50% of all habitat records were from shortgrass

prairie, with sage habitats comprising another 25%. This difference

may be a result of different habitat definitions, since the shortgrass

prairie used by Cassin’s Sparrows undoubtedly includes a shrub

component of some sort.

Cassin’s Sparrows begin arriving in Colorado around mid-April

(Kingery 1998). The first nest record for the state was found near Barr

Lake on June 14, 1907; the nest contained four eggs (Bailey and

Niedrach 1965). The majority of nesting dates occur from early June

through mid-July (Kingery 1998), although Kingery and Julian (1971)

reported a nest with eggs on May 16 in southeast Colorado. Colorado

Bird Observatory (CBO) studies in southeast Colorado observed the

first nest-building behavior in mid-May and the latest nest being

observed for fledging in the first week of August (J. Bradley pers.

commun.).

BBS For the entire time period of available BBS data (1966 - 1996) there was

a somewhat significant decline (P = 0.18; n = 32) of - 4.1 % per year

(Table 3). For 1966 - 1979 there was a significant decline (P = 0.06; n =

8) of - 9.6% per year, and for 1980 - 1996 there was a very significant

increase (P = 0.03; n = 32) of + 2.6% per year (Sauer et al. 1997). To

describe the distribution in the state, Cassin’s Sparrows were found on

all BBS routes in Baca, Prowers, Bent, Otero, Crowley, Pueblo, El

Paso, Lincoln, Cheyenne, Yuma, Washington, Morgan, and Logan

Counties, and on most routes in Las Animas, Kit Carson, Adams, and

Weld Counties (J. R. Sauer unpub. data a). The numbers vary both

annually and geographically. The routes that commonly record more

than 100 birds on a route year after year are all located in the

southeastern part of the state; there are quite a few routes in the

northeastern part of the state that show consistent numbers annually

but they rarely reach 100. There are also examples of the large

fluctuations in population from year to year. A few examples follow: a

route in Lincoln County that commonly had 80 - 120 Cassin’s, with a

maximum of 230; a route in Yuma County that commonly had 40 - 70

with a maximum of 111; a route in Prowers County that in some years

had 25 - 60, other years 120 - 135, and a maximum of 359; and a nearby

route that had anywhere from 5 to 340 (J. R. Sauer unpub. data a).
76 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

CBC N/A

Atlas The Colorado Breeding Bird Atlas (Kingery 1998), for which field data were

collected from 1987 to 1995, provides the most up-to-date information about the

avifauna of Colorado. Breeding Cassin’s Sparrows concentrated in

southeastern Colorado (from Las Animas, Huerfano, Pueblo, and El Paso

Counties east to the border), with many also nesting in the northeastern part of

the state (including portions of Kit Carson, Yuma, Washington, Sedgwick,

Logan, Washington, Morgan, and Weld Counties) (Figure 11 - Atlas map).

With two exceptions (from April), atlas data did not note spring arrival until the

second half of May, but noted that that might be because Cassin’s Sparrows

tend to delay courtship after arrival. The majority of nesting dates occurred

from early June through mid-July. Nearly 50% of all habitat records were from

shortgrass prairie, with sandsage shrubland habitats comprising another 25%.

Perusal of only the confirmed breeding records found a similar pattern with 50 -

60% of the records from shortgrass prairie, primarily in the southeast, and 20%

from either lowland sagebrush habitat in the southeast or tallgrass-sandsage in

the northeast.

Research / Monitoring In response to the need for better monitoring of many Colorado birds

that are not sufficiently monitored by existing programs, Colorado Bird

Observatory and the Colorado Division of Wildlife initiated the

Monitoring 2001 program to develop habitat-based bird monitoring

stations that gather demographic data throughout the state. Cassin’s

Sparrows are classified as a species for which BBS data in Colorado are

inadequate and as a priority species for the Monitoring 2001 program.

It is also targeted by CBO’s Shortgrass Prairie Project (CBO 1997).

The Colorado Bird Observatory has been conducting a number of

projects in southeastern Colorado that include Cassin’s Sparrow as a

target species. Point counts were conducted from 1995 through 1997.

In 1996, a Cassin’s Sparrow nest study produced information on nest

habitat and survivorship; preliminary analyses show that daily survival

rates are quite low on the Comanche National Grasslands (about 0.17

using Mayfield method; n = 27) (J. Bradley pers. commun.). A project

in 1998, in cooperation with the Comanche National Grasslands, focused

on habitat use by singing males. It found that sites where Cassin’s

Sparrows were detected were characterized by 27% bare ground,

14.8% shortgrass, 37.8% midgrass, 8.5% forbs, 2.4% cholla, 4.6% yucca,

0.9% low shrub (<1 m), and 4.1% tall shrub (>1 m) (Gillihan 1999). The

best management practices recommended by CBO for Cassin’s

Sparrows suggest the management of grassland parcels to provide a

mixture of shortgrass and midgrass (40 - 80% total cover), with 20-30%

bare ground, and scattered shrubs (5-35% canopy cover) (Gillihan 1999).

The Colorado Division of Wildlife has initiated a project in southeastern

Colorado (Comanche National Grasslands) that will focus on Cassin’s

Sparrows and several other species. It involves comparing transect

and point count surveys to determine the most effective methods for

surveying birds and developing an index of productivity. In the first

field season (1999), point counts have been conducted on singing male

Cassin’s Sparrows (and other target species), and nest searches have
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 77

Appendix A - State Summaries

found at least six nests (K. Giesen pers. commun.).

Figure 11. Cassin’s Sparrow distribution in Colorado. Shown as blocks of possible, probable, and

confirmed breeding occurrences. From Kingery (1998).

Major Populations The core area for Cassin’s Sparrows in Colorado is the Comanche

National Grasslands in Baca County in the southeastern part of the

state (J. Bradley pers. commun.). In some years the Pawnee National

Grasslands in northeastern Colorado may support smaller populations.

State Status None (K. Giesen pers. commun.).

Colorado Division of Wildlife has developed COVERS, the COlorado

VErtebrate Ranking System, for identifying conservation priorities

among native vertebrates in the state. Based on existing sources of

data and peer review, COVERS employs a two-step ranking system

for identifying species with high conservation needs. A species is

evaluated on its degree of biological imperilment, state of knowledge of

the species, current management status, relative importance of

Colorado populations to species overall, socioeconomic issues, and

additional biological factors. As part of a larger ranking system, the

scores for any one species should be interpreted within the context of

the scores of similar taxonomic groups. Therefore, presenting COVERS

scores for Cassin’s Sparrows alone would not be helpful. However a
78 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

comparison of COVERS biological scores for Cassin’s Sparrows and those of

other grassland birds indicates that Cassin’s Sparrow falls into a low-to-median

position along the continuum of priority grassland bird species in Colorado

(Gross and Melcher 1998).

Natural Heritage Rank State rank - S4B (M. Wunder pers. commun.).

Habitat Condition Knopf (1994) reports that for private land in Colorado, 98,030 km2 of

Colorado’s shortgrass prairie remains as rangeland, with 42,910 km2

now in cropland and 5,100 km2 in pasture-land, based on USDA

numbers in 1987. This does not include public lands, the largest of

which are the Comanche National Grassland (453,707 acres, much in

midgrass and shortgrass prairie), and the Pawnee National Grassland

(193,060 acres interspersed with private and other public lands).

Threats There was very little information available about particular threats

that face Cassin’s Sparrows in Colorado.

Literature Cited Andrews, R. & R. Righter. 1992. Colorado birds. Denver Museum of

Natural History, Denver, CO.

Bailey, A. M. and R. J. Niedrach. 1965. Birds of Colorado. Vol. II.

Denver Museum of Natural History, Denver, CO.

CBO. 1997. Reference guide to the monitoring & conservation status of

Colorado’s breeding birds. Colorado Bird Observatory, Brighton,

CO.

Gillihan, S. W. 1999. Best management practices for select bird species of

the Comanche National Grassland. Report submitted to U.S.

Forest Service, Comanche National Grassland.

Gross, J. E. and C. P. Melcher. 1998. COVERS: Identifying species at

risk and setting priorities for conservation of vertebrates in

Colorado. Unpublished report submitted to Colorado Division of

Wildlife, Fort Collins, CO.

Kingery, H. E. Ed. 1998. Colorado breeding bird atlas. Colorado

Breeding Bird Atlas Partnership, Denver, CO.

Kingery, H. E. & P. R. Julian. 1971. Cassin’s Sparrow parasitized by

cowbird. Wilson Bulletin 83(4): 439.

Knopf, F. L. 1994. Avian assemblages on altered grasslands. Studie in

Avian Biology Number 15: 247-257.

Rising, J. D. 1996. A guide to the identification and natural history of the

sparrows of the United States and Canada. Academic Press, New

York, NY.
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 79

Appendix A - State Summaries

Sauer, J. R. Unpub. data a. North American Breeding Bird Survey results and

analysis. Patuxent Wildlife Research Center, Laurel, MD.

Sauer, J. R., J. E. Hines, G. Gough, I. Thomas, and B. G. Peterjohn. 1997.

The North American Breeding Bird Survey results and analysis.

Version 96.4. Patuxent Wildlife Research Center, Laurel, MD.
80 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

KANSAS Cassin’s Sparrows breed in southwestern Kansas (regularly to

Summary Hamilton, Finney, and Comanche Counties), and less commonly they extend to

Cheyenne County (Johnsgard 1979). Thompson and Ely (1992) describe their

distribution as chiefly south of the Arkansas River but also north to Wallace

County and east to Edwards. They also note that in “irruption” years

populations increase in size and birds occur much further north and east, with

nesting occurring east to Rice County. Cassin’s Sparrows are listed as an

abundant migrant and summer resident, and one of the five most conspicuous

birds on Cimarron National Grassland (Cable et al. 1996).

They are found primarily in rabbitbrush and sandsage grasslands

(Rising 1996; B. Busby pers. commun.). Williams and LeSassier (1968)

reference an earlier report from Kansas that Cassin’s Sparrows

frequent barren spots and sandy lands that have a component of low,

stunted bushes, bunch grass, or cactus. Eggs are laid from mid-May to

mid-July (Johnsgard 1979). Nest dates from the Cimarron National

Grasslands included 2 June, 7 June, 8 June, and 12 June (Cable et al.

1996).

BBS BBS trend data for the state of Kansas are of limited value since there

are so few routes in western Kansas where Cassin’s Sparrows are

found (n = 10 for 1966-1996 time period), and therefore few for which

sufficient, reliable data exist for analysis. As a description of Cassin’s

Sparrow distribution within the state, Cassin’s Sparrows were

observed on routes within Sherman, Wallace, Logan, Gove, Decatur,

Phillips, Ellis, Barton, Kearny, Meade, Clark, Comanche, Barber,

Barber, Pratt, Stafford, and Ottawa Counties. Only the routes in

Kearney, Wallace, and Sherman show consistent records of Cassin’s

Sparrows, with all other routes showing sporadic records of individual

birds. For example - the route in Kearney commonly recorded 15 - 55

with a maximum of 88; the route in Wallace showed some years with

0 - 10, others with 40 - 135, and a maximum of 165 (J. R. Sauer unpub.

data a).

CBC N/A

Atlas Data for the Kansas Breeding Bird Atlas have been collected

(1992 - 1997) and a draft is currently being written. Atlas data (Figure

12) show the highest percentage of records in the southwestern corner

of the state, with almost equal frequency of occurrence in the Red Hills,

but only marginal breeding evidence in the northern High Plains

(Busby and Zimmerman unpub. data). Confirmed nesting records were

in Morton, Stevens, Seward, and Gove Counties. The atlas project did

not gather data on abundance. Cassin’s Sparrow presence is strongly

related to the presence of native shortgrass and mixed-grass prairie

with a shrub component (sagebrush, yucca, etc.). Typically this habitat

was sandsage (Artemesia filifolia) prairie on sandy soils (B. Busby

written commun.).

Research / Monitoring There was not any evidence of research or monitoring programs being

conducted on Cassin’s Sparrows in Kansas, other than the BBS, and the
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 81

Appendix A - State Summaries

BBS coverage in western Kansas is sparse, providing little detail (B. Busby

written commun.). However, the Kansas Department of Wildlife and Parks

has contracted with someone to update their information on the distribution of all

species in the state (J. Horak pers. commun.).

Figure 12. Cassin’s Sparrow distribution in Kansas. Shown as blocks of possible, probable, and confirmed

breeding occurrences. Data were collected from 1992 - 1997, from Busby and Zimmerman (Unpub.

data).

Major Pupulations Cassin’s Sparrows are common to abundant in areas like the Cimarron

National Grasslands and in the sandhills along the south side of the

Arkansas River in Hamilton, Kearny, and Finney Counties (B. Busby

written commun.)

State Status None (B. Busby written commun.).

Natural Heritage Rank State rank - S3B (B. Busby pers. commun.).

Habitat Condition Due to the amount of conversion of sandsage prairie to cropland within

the Kansas range of Cassin’s Sparrow, particularly since 1960, it is

likely that populations have declined substantially. Large amounts of

sandsage prairie along the Arkansas River were converted to irrigated

agriculture in the 1970’s (B. Busby written commun.).

B. Busby (pers. commun.) noted that in Kansas the Cassin’s Sparrow’s

habitat is quite coincident with that of the Lesser Prairie-Chicken

(Tympanuchus pallidicinctus) and that conservation efforts focused on

improving Lesser Prairie-Chicken habitat might also benefit Cassin’s

Sparrows, especially if it involved planting sandsage.
82 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

Threats Brush control in the form of sandsage prairie spraying is a potential threat to

Cassin’s Sparrows in Kansas, as their distribution there is tied to sandsage.

Control was carried out on the Cimarron National Grasslands in the late 1970’s

and early 1980’s but has not been continued since. Habitat loss was also

identified as a threat, but there is not a lot of plowing under of native prairie in

western Kansas, as most of the appropriate arable land has already been

transformed (B. Busby pers. commun.).

Literature Cited Busby, W. and J. Zimmerman, Eds. Unpublished data. Kansas Breeding Bird

Atlas Project, Kansas Biological Survey, Lawrence, KS.

Cable, T. T., S. Seltman, and K. J. Cook. 1996. Birds of Cimarron

National Grassland. USDA Forest Service, General Technical

Report RM-GTR-281.

Johnsgard, P. A. 1979. Birds of the great plains. University of Nebraska

Press, Lincoln, NE.

Rising, J. D. 1996. A guide to the identification and natural history of the

sparrows of the United States and Canada. Academic Press, New

York, NY.

Sauer, J. R. Unpub. data a. North American Breeding Bird Survey

results and analysis. Patuxent Wildlife Research Center, Laurel,

MD.

Thompson, M. C. and C. Ely. 1992. Birds in Kansas. Vol. I. University

Press of Kansas, Lawrence, KS.

Williams, F. C. and A. L. LeSassier. 1968. Cassin’s Sparrow. Pages

981-990 in Life histories of North American cardinals, grosbeaks,

buntings, towhees, finches, sparrows, and allies (O. L. Austin, Jr.,

Ed.). Dover Publications, New York, NY.
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 83

Appendix A - State Summaries

WYOMING Wyoming lies on the extreme northwestern limit of the Cassin’s

Summary Sparrow’s breeding range. Cassin’s Sparrow is considered an accidental

species (Luce et al. 1997). The first record of Cassin’s Sparrow was a singing

male observed on 8 June 1978 in Natrona County (Faanes et al. 1979). Habitat

was described as a south-facing slope with sagebrush and greasewood, with

blue grama and green needlegrass (Stipa viridula) and prickly pear on the

ground layer. There have been additional reports of birds from Platte County

and Goshen County (Dorn and Dorn 1995). The first record of a Cassin’s

Sparrow nest was on 31 July 1993 in Goshen County near the Nebraska border

(Dorn and Dorn 1995). This nest occurred in consolidated rolling sandhills

dominated by sand sagebrush, and at that time contained three feathered young

and one unhatched egg (Dorn and Dorn 1995). However, the Bird Records

Committee in Wyoming has only accepted two sightings, the June 1978 sighting

and a sighting in Goshen County in 1990. The nest report from 1993 was not

accepted because of lack of description of the birds to go with the nest

descriptions (A. Cerovski pers. commun.).

BBS There is insufficient data to produce any BBS trend data for Wyoming.

A single BBS route in Goshen County recorded two Cassin’s Sparrows

one year and one bird in a second year (J. R. Sauer unpub. data a).

CBC N/A

Atlas There isn’t a Wyoming Breeding Bird Atlas. Currently the closest

thing is a document called “The Atlas of Birds, Mammals, Reptiles and

Amphibians in Wyoming” (Luce et al. 1997), produced by the Wyoming

Game and Fish Department. It lists Cassin’s Sparrow as accidental.

Research / Monitoring There are no current research or monitoring projects focused on this

species.

Major Populations There are no major populations of Cassin’s Sparrows in Wyoming. It is

considered an accidental species there, with the possibility that recent

observations represent a range expansion.

State Status None (A. Cerovski pers. commun.).

Natural Heritage Rank State rank - S1 (G. Beauvais pers. commun.); it received this score

because it is on the periphery of its range. The Wyoming Natural

Diversity Database does track this species, collecting any documented

observations. They noted only one breeding record – the observations

from Goshen County near Torrington that are mentioned above.

Habitat Condition Not enough is known to describe habitat condition.

Threats Not enough is known to describe threats.
84 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

Literature Cited Dorn, R. D. and J. L. Dorn. 1995. Cassin’s Sparrow nesting in Wyoming.

Western Birds 26: 104-106.

Faanes, C. A., B. A. Hanson, and H. A. Kantrud. 1979. Cassin’s Sparrow - first

record for Wyoming and recent range extensions. Western Birds 10: 163-

164.

Luce, B., B. Oakleaf, A. Cerovski, L. Hunter, and J. Priday, Eds. 1997.

Atlas of birds, mammals, reptiles, and amphibians in Wyoming. Wyoming

Game and Fish Department, Lander, WY.

Sauer, J. R. Unpub. data a. North American Breeding Bird Survey results and

analysis. Patuxent Wildlife Research Center, Laurel, MD.
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 85

Appendix A - State Summaries

NEBRASKA

Summary Nebraska lies at the northern periphery of the Cassin’s Sparrow breeding range

and it has been variously classified as accidental, or a rare and irregular migrant

and summer resident in southwestern Nebraska (Johnsgard 1996; Ducey 1988).

The first record of a nesting Cassin’s Sparrow was reported in mid-June 1974

in Perkins County (Williams 1974). Other records of singing males were

reported from western and southwestern Nebraska including Perkins, Hayes,

Lincoln, Deuel, Garden, Cheyenne, Sioux, Dundy, Box Butte, Sheridan, and

Morrill Counties (Faanes et al. 1979; Williams 1974; Labedz 1986; Sharpe et al.

unpub. data). In June 1993 Bock and Scharf (1994) discovered a small nesting

population (three nests found) of Cassin’s Sparrows in Keith County. They

were located along an abandoned roadside dominated by perennial mid-height

native grasses with scattered yucca in nearby pastures (Bock and Scharf 1994).

The Nebraska Breeding Bird Atlas project (Sharpe et al. unpub. data) noted

spring arrival in late May and fall departure in August.

BBS Only four BBS routes in Nebraska show a few records of Cassin’s

Sparrows. They are located in Hitchcock, Cheyenne, Morrill, Sioux,

and Scotts Bluff Counties and showed sporadic records of one - seven

birds. There were insufficient data to define any trends (J. R. Sauer

unpub. data a).

CBC N/A

Atlas The Nebraska Breeding Bird Atlas is currently in draft form with

hopes of publication in the next year. The data was collected

approximately ten years ago (Sharpe et al. unpub. data) and the

Nebraska Game and Parks Commission is currently working on getting

this published (J. Dinan pers. commun.). They also hope to begin a

repetition of the atlas data-gathering in the next two years. The draft

species account (Sharpe et al. unpub. data) describes Cassin’s Sparrows

as rare breeders and spring and fall migrants in the west and

southwest parts of the state. It notes that they occur in grasslands

containing good stands of sandsage, primarily in the southwest and

southern panhandle of the state.

Research / Monitoring No projects occur other than BBS routes.

Major Populations There are not any major populations in the state.

State Status None. It is considered an accidental species in the state.

Natural Heritage Rank State rank - S4.

Habitat Condition There is not sufficient information to make a statement on the condition

of habitat in Nebraska for this species.

Threats There is not sufficient information to describe threats.
86 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

Literature Cited Bock, C. E. and W. C. Scharf. 1994. A nesting population of Cassin’s Sparrows

in the sandhills of Nebraska. Journal of Field Ornithology 65(4): 472-475.

Ducey, J. E. 1988. Nebraska Birds: Breeding Status and Distribution. SimmonsBoardman Books, Omaha, NE.

Faanes, C. A., B. A. Hanson, and H. A. Kantrud. 1979. Cassin’s Sparrow - first

record for Wyoming and recent range extensions. Western Birds 10: 163-

164.

Johnsgard, P. A. 1996. The birds of Nebraska and adjacent plains states.

Nebraska Ornithological Union. Occasional Papers, No. 6.

Labedz, T. E. 1986. Cassin’s Sparrow in Garden County. Nebraska Bird

Review 54: 80-81.

Sauer, J. R. Unpub. data a. North American Breeding Bird Survey

results and analysis. Patuxent Wildlife Research Center, Laurel,

MD.

Sharpe, R., J. Jorgensen, and R. Silcock. Unpublished data. Birds of

Nebraska, their distribution and ecology. Nebraska Breeding Bird

Atlas Project. Nebraska Game and Parks Commission, Lincoln,

NE.

Williams, F. 1974. Southern Great Plains. American Birds 28: 922.
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 87

Appendix A - State Summaries

MEXICO

State Sonora, Chihuahua, Coahuila, Tamaulipas, Sinaloa, Nayarit, Nuevo León,

Zacatecas, Guanajuato, Durango, Jalisco, San Luis Potosí

Summary Howell and Webb (1995) report Cassin’s Sparrow as a fairly common to

common breeder in northern Sonora, in the interior south on the

Mexican Plateau at least to Zacatecas and San Luis Potosí, and on the

Atlantic slope in Tamaulipas. They report that although they are resident in

much of this range there is probably some withdrawal south in the winter. They

describe Cassin’s Sparrow habitat in Mexico as arid to semiarid, open and

semiopen brush, and grassland with scattered bushes and brush. They note

breeding in Mexico from April through September. Cassin’s Sparrows are

uncommon to fairly common in winter on the Pacific slope from Sonora to

Nayarit, and south in the interior to Guanajuato (Howell and Webb 1995).

Russell and Monson (1998) also found Cassin’s Sparrows wintering rather

commonly through much of Sonora, especially south of the latitude of

Hermosillo. They reported that winter numbers are dependent upon

availability of grasslands (or weedy places) with a component of shrubs,

characteristics which are dependent on favorable summer rains and

little or no grazing.

BBS A three-year BBS feasibility study was conducted in Mexico from

1993 - 1996. Routes that recorded Cassin’s Sparrows were located in

Coahuila near Saltillo, Ocampo, etc. and in Tamaulipas near Aldama.

For these few years most records were for only a few birds; one route

in northern Coahuila recorded 30 Cassin’s Sparrows one year and

another in northern Coahuila recorded 65 in one year (J. R. Sauer

unpub. data a). None of those routes have been surveyed subsequently.

With the exception of a couple of routes that are sporadically surveyed

by U.S. citizens, the BBS does not exist in Mexico at this time.

However, there is interest in Mexico in developing a program to

monitor bird populations, that may include a BBS in portions of the

country. Some discussions have been held and BBS anticipates some

preliminary action within the next year or so (B. Peterjohn pers.

commun.). Expansion of the BBS program, or an equivalent, into

Mexico could potentially provide valuable information about Cassin’s

Sparrow populations there.

CBC A number of CBCs are conducted in Mexico by coalitions of U.S.,

Mexican, and in some cases Canadian citizens, primarily in Sonora,

Chihuahua, and Tamaulipas, although there is no organized program

for the country. Additional cooperation from and support for Mexican

participation in this program would be valuable. Several CBC circles in

Sonora have recorded Cassin’s Sparrows in one or two years

(Bavíacora, Yécora, and Alamos), several in Chihuahua (Rancho el

Palomina and Ejido San Pedro), one in Guanajuato (San Miguel de

Allende), and the Rio Corona circle in Tamaulipas consistently showed

10-20 Cassin’s from 1991 to 1994 (J. R. Sauer unpub. data b).

Atlas N/A
88 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

Research / Monitoring A study of the seasonal fluctuations in seed-eating bird populations across three

habitat types along a topographic gradient in the central Chihuahuan Desert in

Mexico (Nocedal, in prep) was conducted from 1978-1981. Of the three

habitat types – upper bajada (upper mountain slopes and alluvial fans), lower

bajada, and playa (seasonally flooded bottomlands) – Cassin’s Sparrows were

found most consistently and most abundantly in the lower bajada habitats

characterized by a shrub component of mesquite, creosote bush, tar bush, etc.

and a grass under story (summer 1978 - 5.9/10 ha; winter 1979 - 5.5/10 ha;

summer 1979 - 4.9/10 ha; winter 1980 - 0.2/10 ha). They were also found

during one winter and summer season in the playa habitat (winter 1979 - 11.8/

10 ha; summer 1979 - 5.7/10 ha). Nocedal suggests that they were able to use

the playa habitat as a result of larger than average seed crops due to optimal

rainfall patterns during and in the previous season. Cassin’s Sparrows appeared

to abandon the study area during the final summer and winter field season.

In 1996, the Colorado Bird Observatory (CBO) initiated a long-term winter

project in the grasslands of Chihuahua and Durango, Mexico. The objectives

are to determine distribution patterns of wintering grassland birds on the

Mexican Plateau, determine habitat associated with target species, and monitor

population trends over time. CBO completed a pilot season in the winter of

1995-1996 (Bradley and Leukering, 1996) and two years of data collection

(1996-97 and 1997-98). Most of their surveys to date have been conducted in

Chihuahua. They survey birds using the area search method and collect

related vegetation data. Cassin’s Sparrows were found on 27 of 384 area

search plots during 1997 (Carter et al. 1997), and on 29 of 445 plots during 1998

(Carter et al. 1998). They were generally found skulking in thick cover, usually

grass, with available perch sites. Using both a Principal Components Analysis

(PCA) and a univariate approach (Table 8) on 1997 data, they were found to be

present on sites with higher than average shrub cover, bare ground, litter, and

tall grass.

Table 8. Sample size and means for untransformed vegetation variables associated with wintering

grassland bird species on the Mexican Plateau of Chihuahua, Mexico. First 4 vegetation

variables present number of point-intercepts where that type of vegetation was found;

vertical grass presents the number of grass intercepts at the 30 - 40 cm height; percent

shrub presents a visual estimate of percent shrub cover. Values that are bolded are greater

than the mean for all plots (no statistical analysis was provided). From Carter et al. (1997).

Species n Bare Forbs Grass Litter VerticalPercent Shrub

Ground Grass Cover (>1 m)

Cassin’s 27 49.48 6.82 71.52 31.00 14.93 4.56

Sparrow

All Plots 384 43.47 7.18 78.56 29.41 12.57 3.03

Using PCA and univariate analysis (Table 9) on a slightly different set

of vegetative variables in 1998, Cassin’s Sparrows were found at sites

with more shrubs and trees with a grass component (Carter et al. 1998).

General observations of Cassin’s Sparrows noted that they were most

often found in areas with shrub cover and at least clumps of dense grass. They

were most often flushed from dense grass but tended to drop back into or next

to the bases of shrubs.
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 89

Appendix A - State Summaries

Table 9. Sample size and means for untransformed vegetation variables and habitat associations of

wintering grassland bird species on the Mexican Plateau of Chihuahua, Mexico. Values

greater than the mean for all plots are bold (no statistical analysis was provided). First

three vegetation variables represent cover estimates. Point quarter variables present the

mean distance to the nearest cactus (or shrub or tree) in each of 4 quadrants. From Carter

et al. (1998).

Species n Bare Forbs Grass Cactus Shrub Tree

Ground Pt. Qtr. Pt.Qtr. Qtr.

Cassin’s 29 21.43 11.43 67.14 24.63 141.73 66.73

Sparrow

All Plots 445 24.44 13.90 60.10 18.96 94.33 58.65

A graduate student at the Universidad Autónoma de Chihuahua is

currently gathering data for a master’s thesis on “Relative abundance

and biomass of grassland birds in Aplomado Falcon territories in

Chihuahua, Mexico” (C. Mendez-Gonzales et al. written commun.). He

has shared the raw data on Cassin’s Sparrows from his first year of

data collection for this report. The study areas are in north-central

Chihuahua in the Counties of Villa Ahumada and Chihuahua in the

Sueco zone, and the County of Coyame in the Tinaja Verde zone.

During the breeding season (August), he recorded a total of 152

Cassin’s Sparrows on plots at the Sueco site and 131 Cassin’s Sparrows

on plots at the Tinaja Verde site. Using a conservative approach

(assuming that 50% of the individuals recorded during area searches

were male and 50% female, and thus halving total numbers to calculate

pair density), preliminary estimates of breeding density were 0.39 pairs

per ha at Sueco and 0.34 pairs per ha at Tinaja Verde. By gathering

vegetation data on basal cover and shrub density, he will be able to

compare plots where particular species were found, with plots where

they are absent (Table 10). There do not appear to be many consistent

patterns between the two sites after one year of data collection, but

additional data collection and analysis may clarify this. MendezGonzalez felt that at the Sueco site Cassin’s Sparrows were probably

responding to grass cover and litter rather than shrub density, whereas

at the Tinaja Verde site they seemed to be more clearly responding to

shrub density. This study also distinguishes six different habitat types

within the plots sampled. The sample sizes for Cassin’s Sparrows are

too low and the variance too high to make statistical comparisons at

this time for differences in habitat preference. With the exception of

open grasslands on hills which did not support any Cassin’s Sparrows at

either Sueco or Tinaja Verde, the other habitat types - shrub grassland,

swale, open grassland, savannah, and yucca grassland - all supported

mean individuals per plot ranging from 1.33 to 3.0, with no clear pattern

of preference for certain habitat types.
90 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries

Table 10. Average percentage of basal cover and shrub density in plots where breeding Cassin’s Sparrows were

present and absent - preliminary data from one year (Mendez-Gonzalez written commun.)

Location Status Grass Litter Herb. Shrubs Bare Shrub

Vegetation Ground Density

Sueco Present 47.27 38.55 0.45 0.88 17.86 98.90

Sueco Absent 19.06 17.81 0.69 1.44 61.00 282.19

Tinaja Present 37.71 34.53 0.22 1.22 26.31 197.00

Verde

Tinaja Absent 36.19 48.75 1.69 2.12 11.25 99.50

Verde

During the nonbreeding season, surveys were conducted in January,

March-April, and May-June. During those time periods he recorded 7,

16, and 0 Cassin’s Sparrows respectively at the Sueco site and 5, 5, and

7 Cassin’s respectively at the Tinaja Verde site. A preliminary

estimate of Cassin’s Sparrow wintering density for those time periods found

densities of 0.36, 0.82, and 0 individuals per ha respectively for Sueco, and 0.26,

0.26, and 0.36 individuals per ha respectively for Tinaja Verde.

Although most of her research was in southern New Mexico, Meents

(1979) studied the bird community at a site in northern Chihuahua (La

Campana). She provides information about average census numbers

for Cassin’s Sparrows at each site. Along 7.2 km roadside censuses,

74.0 Cassin’s Sparrows were recorded in summer and 1.0 in winter at

La Campana.

Major Populations There is insufficient information to describe locations of major

populations of Cassin’s Sparrows in Mexico, although there is reason to

believe that substantial populations of breeding Cassin’s Sparrows

exist in the grasslands of Sonora, Chihuahua, etc. In addition, Mexican

grasslands provide the great majority of wintering habitat for the

entire population of Cassin’s Sparrows.

State Status No evidence was found of any particular status designations of Cassin’s

Sparrows in Mexican states.

Natural Heritage Ramk N/A

Habitat Condition Insufficient information is available to make statements about this.

One of the CBO reports (Carter et al. 1998) provided the following

information: “Within the state of Chihuahua the principal habitats are

desert scrub (41%), pine forest (16%), and farm/pasture lands (36%)

(Flores Villela and Gerez 1994). The proportion of the latter underwent

a 7% increase in the decade between 1981 and 1992 as the overall

proportion of perturbed lands increased. While governmental data

indicate that as recently as 1981, 24% of the state was undisturbed

grassland, more recent federal assessments do not recognize any

natural grasslands remaining in the state (Flores Villela and Gerez

1994).”
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999 91

Appendix A - State Summaries

Threats Insufficient information is available to make statements about this.

Literature Cited Bradley, J. S. and T. Leukering. 1996. Distribution and habitat associations of

birds wintering in Mexican grasslands: 1996 pilot season report. Report

submitted to NPS (Howard Ness).

Carter, M. F., T. Leukering, J. S. Bradley, & C. S. Aid. 1997. Habitat

associations of the Mexican Plateau winter grassland bird

community. Report submitted to USFWS (Bill Howe) & NPS

(Howard Ness).

Carter, M. F., T. Leukering, and S. Hutchings. 1998. Distribution & habitat

associations of Mexican Plateau winter grassland bird community. Report

submitted to USFWS (Bill Howe) & NPS (Howard Ness).

Flores Villela, O. and P. Gerez. 1994. Biodiversidad y conservación en

México: vertebrados, vegetación y uso del suelo (Biodiversity &

conservation in Mexico: vertebrates, vegetation and land use).

Universidad Nacional Autónoma de México, México, D.F.

Howell, S. N. G. and S. Webb. 1995. A guide to the birds of Mexico &

northern Central America. Oxford University Press, Oxford,

England.

Meents, J. K. 1979. Avian community structure in Chihuahuan desert

grasslands. Ph.D. dissertation. New Mexico State University, Las

Cruces, NM.

Mendez-Gonzalez, C. E., A. Lafon, and R. A. Meyer. Written

communication. Relative abundance & biomass of grassland birds in

Aplomado Falcon territories in Chihuahua Mexico. Data from M.S.

thesis research. Universidad Autónoma de Chihuahua.

Nocedal, J. In prep. Seasonal dynamics of populations of seed-eating

birds in arid grasslands of central Chihuahuan Desert. For

submission to Journal of Field Ornithology.

Russell, S. and G. Monson. 1998. The birds of Sonora. University of

Arizona Press, Tucson.

Sauer, J. R. Unpub. data a. North American Breeding Bird Survey

results and analysis. Patuxent Wildlife Research Center,

Laurel, MD.

Sauer, J. R. Unpub. data b. Christmas Bird Count results. Patuxent

Wildlife Research Center, Laurel, MD.
92 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 1999

Appendix A - State Summaries
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 93

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B: H

A

BITA

T

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Table B1. General habitat descriptions for major references used in this document (where available).

See Table C2 for list of scientific names associated with common names used here.

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Bock and Bock 1978; Bock and Bock1988; Bock and Bock 1992; Bock et al.1984; Bock et al. 1986; Bock et al.1992; Bock and Webb 1984; Webb andBock 1990

Appleton-Whittell Research Ranch(AWRR) and surrounding lands;Santa Cruz & Cochise Counties, AZ

Mean precip. = 43 cm, mostly July -Sept.; mean elev. = 1500 m; livestockhas been excluded from the AWRRsince 1968.(1) Upland mesa sites preferred byCassin’s Sparrows: densely covered byperennial grasses (blue & sideoatsgrama, plains lovegrass, curlymesquite, wolftail & threeawn), exoticgrasses (Lehman lovegrass), scatteredmesquite & catclaw acacia, and lowshrubs (velvet–pod, wait-a-minute,Yerbe de Pasmo, rabbitbrush,goldenweed & groundsel)

(1) Upland structural dgrazing, firtreatments presented e

(2) Floodplains - broad stands of nearlymonotypic sacaton over 2 m high

(2) Floodplpoints samp(74 %); othbare ground 

Maurer 1985; Maurer 1986 Santa Rita Experimental Range

(SRER), Pima County, AZ

Mean precip. = 20-40 cm from lowelevations to the foothills; Dominantshrubs (mesquite, Opuntia cactusspecies, burroweed, acacias, ocotillo,mimosas & false mesquite); nativeperennials (Arizona cottontop,threeawn, bush muhly, severalperennial gramas); and the exoticLehman lovegrass

Mesquite d162/ha; meranged from 
94 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

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Flesch 1997; Gordon and Leitner 1996 Buenos Aires National Wildlife

Refuge, Pima County, AZ

Mean precip. = 41.4 cm, with summerpeak in July & Aug. and smaller winterpeak from Dec. to Feb.; elev. range of950 - 1150 m; livestock have beenexcluded since its establishment in 1985;mesquite-grassland with varyingdensities and size classes of mesquite;snakeweed and burroweed arewidespread; vast majority of grass isperennial bunchgrass, with some areasdominated by natives and others by theexotic Lehman lovegrass

Some data Leitner 199# of plants = 232/ha; = 9.5 %; m

Schnase 1984; Schnase and Maxwell1989; Schnase et al. 1991

Angelo State University Management,Instruction and Research area, TomGreen County, TX

Mean precip. = 50 cm, mostly in May andSept.-Oct.; mean elev. = 587 m; Mesquitemixed grass prairie, having large, opengrassland savannahs bordered bymesquite thickets. Dominant shrubs(honey mesquite, Texas prickly pearcactus) and mid- to short grasses (nospecies listed)

Mesquite dopen areas prickly peain open areareas

Meents 1979 (1) Otero Mesa, Otero County, NM (1) Otero Mesa - Elev. = 1480 m; mean

precip. = 33.9 cm; dominant grasses (bluegrama and black grama); dominant shrub(yucca)

(1) Otero M%); forbs (7area (10.6%(64.6 %); s3/ha)

(2) Nutt, Sierra County, NM

(3) Cloverdale, Hidalgo County, NM (3) Cloverdale - Elev. = 1616 m; mean

precip. = 37.6 cm; dominated by bluegrama and buffalo grass

(2) Nutt - Elev. = 1700 m; mean precip. =33.8 cm; dominant grass (curly mesquite);dominant shrubs (yucca & ephedra)

(2) Nutt - % (7.5%); shrulitter (27.2 shrub densi(3) Cloverdforbs (8.9 %(18.3 %); li(58.6 %); sha)
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 95

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Meents 1979 (cont.) (4) La Campana, Chihuahua, Mexico (4) La Campana - Elev. = 1500 m; mean

precip. = 38.1 cm; shrub cover is sparseto heavy; dominant grasses (threeawn);dominant shrubs (mimosa and brickellbush)

(4) La Cam%); forbs (8area (6.2 %(70.7 %); s- 695/ha)

Cole and Ligon 1978; Ligonet al. 1981

Los Medaños Isolation Pilot Plant,Eddy and Lea Counties, southeasternNew Mexico

(1) Mesquite-grasslandDominant shrubs - snakeweed andmesquite

(1) Mesquicover - graslitter (24.1 shrub dens

(2) CreosoteDominant shrubs - creosote, rangeratany, snakeweed, mesquite, andprickly pear

(2) Creosotgrass (18.2 %); bare grdensity = 4

(3) Hummock-mesquite #1Dominant shrubs - Sand sagebrush,rabbitbrush, snakeweed, mesquite, shinoak

(3) Hummoground cov%); litter (1Total shrub 

(4) Hummock-mesquite #2Dominant shrubs - Sand sagebrush,primrose, snakeweed, mesquite, shin oak

(4) Hummoground cov%); litter (2Total shrub 

Maxwell 1979 Concho Valley, Irion, Sterling & Tom

Green Counties + parts of sev. othercounties, TX

Mean precip. = 41 - 61 cm, maximum inMay and Sept.; Maxwell characterized 8major vegetation types - I present hereonly those sites having the largestnumbers of Cassin’s Sparrows;

(1) Scrubby mesquite grassland - Dominant shrub was mesquite, but alsoincluded tasajillo, prickly pear, lotebush,agarita, and small-leaf sumac;herbaceous (threeawn, annualbroomweed, tobosa & buffalo grass)

(1) Scrubby trees absen717/ha; folibut foliar g3.1 m only 22%; foliagveg. cover 
96 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

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Maxwell 1979 (cont.) Concho Valley, Irion, Sterling & Tom

Green Counties + parts of sev. othercounties, TX (cont.)

(2) Grassland - Dominant shrubs (yucca,prickly pear, & sacahuista); herbaceous(cup grass, threeawn, buffalo grass &tobosa)

(2) Grasslanto 1.2 m bubetween 0.3 foliage ht. cover = 94(3) Defoliatextended to 1.2 m was percent veg

(3) Defoliated mesquite (historically) - Dominant trees (mesquite); dominantshrubs (mesquite, tasajillo, lotebush);herbaceous (red grama, lovegrass,annual broomweed, threeawn & buffalograss)(4) Upland mesquite woodland - Dominant tree (mesquite); dominantshrubs (mesquite, tasajillo, agarita 

&

lotebush); herbaceous (hairy grama,curly mesquite & threeawn)

(4) Upland profile extevolume betwht. diversity 129

(5) Bottom mesquite woodland - Dominant trees (mesquite, hackberry 

&

chisumwood); dominant shrubs (pricklypear, tasajillo & mesquite); herbaceous(Texas winter grass, annual broomweed,tobosa and buffalo grass)

(5) Bottom profile extevol. betweediversity = = 126

Welder Wildlife Refuge, nearSinton, TX

Emlen 1972 (1) Grass-forb prairie - Fields of bunch

grass (Andropogon sp. and others) with afew small and medium-sized shrubs

(1) Grass-fo& forbs

(2) Scrubby grasslands - Grass (buffalograss & others) interspersed with large,sparse patches of low-running mesquite,a few larger shrubs and small trees

(2) Scrubby & forbs; 40 
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 97

(3) Open brushland - Similar to scrubbygrassland but many scattered patches of1.5 - 2.0 m dense shrubs and reducedamts. of running mesquite

(3) Open br30 % creep

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Emlen 1972 (cont.) Welder Wildlife Refuge, near

Sinton, TX (cont.)

(4) Dense brushland - Similar to scrubbygrassland but with more and largerclumps of 1.5 - 2.0 m shrubs; buffalo grasslargely replaced by bristle grass asdominant

(4) Dense bforbs; 20 % shrubs

(5) Two-layered brushland - Similar todense brushland but with a layer ofscattered 3.0 - 4.0 m mesquite and acaciashrubs above dominant brush stratum

(5) Two-lay& forbs; 10 shrubs; 10 

(6) Oak woodland - Open stands of liveoak trees over a mixed assemblage oftall shrubs, low shrub clumps, and opengrass on sandy soils

(6) Oak wo15 % creep% tall shrub

(7) Riverine forest - Dense or mediumdense bottomland woods with vines andthickets occurring in narrow strips nearthe river.

(7) Riverine 10 % low strees
98 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

Appendix B: Habitat Descriptions

Table B2.

Common names and scientific names for plant species referenced in Table B1

Common Name Scientific Name

Grasses grama grass Bouteloua spp.

red grama B. trifida

blue grama B. gracilis

sideoats grama B. curtipendula

black grama B. eriopoda

hairy grama B. hirsuta

lovegrass Eragrostis spp.

plains lovegrass E. intermedia

Lehman lovegrass E. lehmanniana

tobosa Hilaria mutica

curly mesquite H. belangeri

wolftail Lycurus phleoides

threeawn Aristida spp.

sacaton Sporobolus airoides (wrightii)

Arizona cottontop Trichachne californica

bush muhly Muhlenbergia porteri

buffalo grass Buchloe dactyloides

cupgrass Eriochloa spp.

bluestem/beardgrass Andropogon spp.

Texas wintergrass Stipa leucotricha

bristlegrass Setaria leucopila

Forbs goldenweed Happlopappus tenuisectus

groundsel Senecio spp.

annual broomweed Amphiachris dracunculoides

Shrubs mimosa Mimosa spp.

wait-a-minute bush M. biuncifera

velvet-pod M. dysocarpa

Yerba-de-Pasmo Baccharis pteronioides

snakeweed Gutierrezia sarothrae

acacia Acacia spp.

catclaw acacia A. greggii

rabbitbrush Chrysothanmus species

burroweed Isocoma tenuisecta

mesquite Prosopis spp.

honey mesquite P. glandulosa

false mesquite Calliandra eriophylla

ephedra Ephedra spp.

creosote Larrea tridentata

sand sagebrush Artemesia filifolia

primrose Calylophus drummondianus

agarita Berberis trifolialata

lotebush Ziziphus obtusifolia

small-leaf sumac Rhus microphylla

hackberry Celtis reticulata
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 99

Appendix B: Habitat Descriptions

Table B2. (cont.)

Common names and scientific names for plant species referenced in Table B1 (cont.)

Common Name Scientific Name

Shrubs (cont.) chisumwood Bumelia lanuginosa

brickell bush Brickellia spinulosa

range ratany Krameria glandulosa (parvifolia)

Cacti, Succulents, etc. prickly pear cactus Opuntia spp.

Texas prickly pear cactus O. lindheimeri

prickly pear O. phaeacantha

tasajillo O. lindheimeri

Ocotillo Fouquieria splendens

Yucca Yucca spp.

sacahuista Nolina texana

Trees oak Quercus spp.

shin oak Q. harvardii

live-oak Q. virginiana
100 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

Appendix B: Habitat Descriptions
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 101

APPENDIX C: LIST OF PRIMARY INDIVIDUALS CONTACTED

Marilyn Altenbach

New Mexico

Natural Heritage Program

University of New Mexico

Department of Biology

851 University Blvd. SE, Ste. 101

Albuquerque, NM 87131

505-272-3545 Ext. 231

altenbac@sevilleta.unm.edu

Carla Alford

Bureau of Land Management

198 Neel Avenue NW

Socorro, NM 87801

505-835-0412

505-835-0223 fax

calford@nm.blm.gov

Wylie Barrow

USGS

National Wetlands Research Center

700 Cajundome Blvd.

Lafayette, LA 70506

318/266-8668

wylie_barrow@usgs.gov

Carol Beardmore

Partners in Flight

Western Regional Coordinator

Arizona Game & Fish

2221 W. Greenway Rd.

Phoenix, AZ 85023-4312

602-789-3502

602-789-3926 fax

cbeardmore@gf.state.az.us

Gary Beauvais

Zoologist

Wyoming

Natural Diversity Database

P.O. Box 3381

Laramie, WY 82071-3381

307-745-5026

Karen L. P. Benson

Co-Editor

Texas Breeding Bird Atlas Project

WFSC, TAMU

College Station, TX 77843-2258

512-993-6095

Dr. Carl E. Bock

Department of EPO Biology

University of Colorado

Boulder, CO 80309-0334

303-492-7184

APPENDIX C:

List Of Primary

Individuals Contacted

Jim Bradley

Colorado Bird Observatory

13401 Piccadilly Road

Brighton, CO 80601

303-659-4348

Kelly B. Bryan

Resource Coordinator

Texas Parks & Wildlife Department

P.O. Box 948

Fort Davis, TX 9734

915-426-3897

Bill Busby

Kansas Biological Survey

2041 Constant Ave.

Foley Hall

University of Kansas

Lawrence, KS 66047-2906

913-864-7692

w_busby@ukans.edu

Mike Carter

Colorado Bird Observatory

13401 Piccadilly Road

Brighton, CO 80601

303-659-4348

mike.carter@cbobirds.org

Andrea Cerovski

Nongame Bird Biologist

Wyoming Game & Fish Department

260 Buena Vista

Lander, WY 82520

307-332-7723 Ext. 232

307-332-6669 fax

acerov@missc.state.wy.us

Troy Corman

Arizona Game & Fish Dept.

2221 W. Greenway Rd.

Phoenix, AZ 85023-4312

602-789-3508

tcorman@gf.state.az.us

John Dinan

Nongame Bird Program Manager

Nebraska Game &

Parks Commission

2200 N. 33rd St.

Lincoln, NE 68503-0370

402-471-5440

402-471-5528 fax

jdinan@ngpsun.ngpc.state.ne.us
102 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

APPENDIX C: LIST OF PRIMARY INDIVIDUALS CONTACTED

Bill Howe

Region 2 Nongame Bird Coordinator

U.S. Fish & Wildlife Service

P.O. Box 1306

Albuquerque, NM 87103

505-248-6875

505-248-7885 fax

bill_howe@fws.gov

Mark Howery

Natural Resources Section

Oklahoma Department

of Wildlife Conservation

1801 N. Lincoln Blvd.

Oklahoma City, OK 73105

405-521-4619

405-521-6535 fax

mhowery@odwc.state.ok.us

Chuck Hunter

Region 4 Nongame Bird Coordinator

US Fish & Wildlife Service

1875 Century Blvd.

Atlanta, GA 30345

404-679-7130

fax 404-679-7285

chuck_hunter@fws.gov

Stephanie L. Jones

Region 6 Nongame Bird Coordinator

U.S. Fish & Wildlife Service

P.O. Box 25486

Denver Federal Center

Denver, CO 80225

303-236-8145 Ext 608 (w)

303-236-8680 fax

stephanie_jones@fws.gov

Hugh Kingery

Colorado

Breeding Bird Atlas Project

P.O. Box 584

Franktown, CO 80116

303-814-2723

ouzels@juno.com

Fritz Knopf

USGS Midcontinent

Ecological Science Center

4512 McMurry Ave.

Fort Collins, CO 80525

970-226-9462

970-226-9230 fax

fritz_knopf@usgs.gov

John B. (“Barny”) Dunning Jr.

Dept. of Forestry

& Natural Resources

Purdue University

West Layfayette, IN 47907

765-494-3565

bdunning@fnr.purdue.edu

Aaron Flesch (contractor)

Buenos Aires

National Wildlife Refuge

P.O. Box 109

Sasabe, AZ 85633

520-823-4251

520-823-4247 fax

Adflesch@aol.com

Ken Giesen

Colorado Division of Wildlife

317 W. Prospect

Fort Collins, CO 80526

970-472-4359

ken.giesen@state.co.us

Caleb Gordon

Dept. of Ecology &

Evolutionary Biology

Bioscience West Room 310

University of Arizona

Tucson, AZ 85721

520-621-3458 (lab)

520-318-0651 (home)

fax 520-621-9190

calebg@u.arizona.edu

Joseph A. Grzybowski

715 Elmwood Dr.

Norman, OK 73072-6118

405-360-0182

grzybow@aix1.ucok.edu

Kevin Gutzwiller

Associate Professor

Department of Biology

Baylor University

Waco, TX 76798-7388

254-710-6557

254-710-2969 fax

kevin_gutzwiller@baylor.edu

Jerry Horak

Kansas Department

of Wildlife & Parks

Emporia Research & Survey Office

1830 Merchant, P.O. Box 1525

Emporia, KS 66802-1525

316-342-0658 Ext. 211
U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000 103

APPENDIX C: LIST OF PRIMARY INDIVIDUALS CONTACTED

David J. Krueper

Avian Senior Technical Specialist

BLM - San Pedro Project Office

1763 Paseo San Luis

Sierra Vista, AZ 85635

520-458-3559

dkrueper@az.blm.gov

Bob Leachman

Ecological Services

U.S. Fish & Wildlife Service

764 Horizon Drive, Building B

Grand Junction, CO 81506-3946

970-243-2778

robert_leachman@fws.gov

Steve J. Lewis

USFWS Region 3

Nongame Coordinator

U.S. Fish & Wildlife Service

Federal Building

1 Federal Drive

Fort Snelling, MN 55111-4056

612-713-5473

612-713-5286 fax

steve_j_lewis@fws.gov

Brian Locke

Fort Bliss

Directorate of Environment

Conservation Division

Bldg. 622, Pleasanton Rd.

Fort Bliss, TX 79916-5000

915-568-3016

915-568-3548 fax

lockeb@emh10.bliss.army.mil

Cynthia Melcher

USGS Midcontinent

Ecological Science Center

4512 McMurry Ave.

Fort Collins, CO 80525

970-226-9258

cynthia_melcher@usgs.gov

César E. Méndez-González

Chihuahua, Mexico

cesarmendez77@hotmail.com

Ray Meyer

La Tierra Environmental Consulting

226 W. Willoughby

Las Cruces, NM 88005

505-541-5853

latierra@zianet.com

Arnold S. Moorhouse

P.O. Box 1023

Douglas, AZ

520-364-3178

Jorge Nocedal

c/o Colorado Bird Observatory

13401 Piccadilly Rd.

Brighton, CO 80601

303-659-4348

Dr. Robert D. Ohmart

Center for Environmental Studies

Arizona State University

Tempe, AZ 85287

602-965-4632

Brent Ortego

Texas Parks & Wildlife Department

2601 N. Azalia; Suite 31

Victoria, TX 77901

512-576-0022

bortego@viptx.net

Bruce Peterjohn

USGS Patuxent

Wildlife Research Center

12100 Beech Forest Road, STE 4038

Laurel, MD 20708-4038

301-497-5841

bruce_peterjohn@usgs.gov

Anna Pidgeon

University of Wisconsin

College of Agricultural

& Life Sciences

Department of Wildlife Ecology

226 Russell Labs

1630 Linden Drive

Madison, WI 53706-1598

608-265-2665

apidgeon@facstaff.wisc.edu

Jeff Price

6525 Gunpark Drive

Suite 150-146

Boulder, CO 80301

303-530-7239

jprice@mho.net

Dan Reinking

Sutton Avian Research Center

P.O. Box 2007

Bartlesville, OK 74005

918-336-7778

918-336-7783

gmsarc@aol.com
104 U.S. Fish and Wildlife Service - Status Assessment and Conservation Plan Cassin’s Sparrow - March 2000

APPENDIX C: LIST OF PRIMARY INDIVIDUALS CONTACTED

Steve Russell

2850 N. Camino de Oeste

Tucson, AZ 85745

520-743-9707

srussell@u.arizona.edu

Christopher Rustay

Hawks Aloft

P.O. Box 10028

Albuquerque, NM 87184

505-892-3354

John R. Sauer

USGS Patuxent

Wildlife Research Center

11510 American Holly Drive

Laurel, MD 20708-4017

301-497-5662

john_r_sauer@usgs.gov

Sabra Schwartz

Arizona Natural Heritage Program

602-789-3618

Hart Schwarz

317 Palomas Drive NE; #9

Albuquerque, NM 87108

505-761-4650 Ext. 357 (w)

Dorinda Scott

Data Manager

Texas Parks & Wildlife Department

Austin, TX

512-912-7023

Chuck Sexton

Wildlife Biologist

Balcones Canyonlands NWR

10711 Burnet Road, Suite 201

Austin, TX 78758

512-339-9432

chuck_sexton@fws.gov

Clifford Shackelford

Texas Parks

& Wildlife Department

4200 Smith School Road

Austin, TX 78744

512-389-4970

512-389-4388 fax

clifford.shackelford@tpwd.state.tx.us

Tom Shane

1706 Belmont

P.O. Box 876

Garden City, KA 67846

316-275-4616

316-275-9476 fax

Susan Skagen

USGS Midcontinent

Ecological Science Center

4512 McMurry Ave.

Fort Collins, CO 80525

970-226-0461

970-226-9230 fax

susan_skagen@usgs.gov

Sartor (Sandy) O. Williams III

New Mexico

Department of Game & Fish

P.O. Box 25112

Santa Fe, NM 87504

505-827-9914

Mike Wunder

Colorado Natural Heritage Program

Colorado State University

254 General Services Building

Fort Collins, CO 80523

970-491-2841

970-491-3349 fax

mbw@lamar.colostate.edu