A Natural History Summary and Survey Protocol for the 

Southwestern Willow Flycatcher

Chapter 10 of

Section A, Biological Science

Book 2, Collection of Environmental Data

Techniques and Methods 2A-10 

Prepared in cooperation with the Bureau of Reclamation and the U.S. Fish and Wildlife Service

U.S. Department of the Interior

U.S. Geological Survey
Cover: Southwestern Willow Flycatcher. Photograph taken by Susan Sferra, U.S. Fish and Wildlife Service. 
A Natural History Summary and Survey Protocol for the 

Southwestern Willow Flycatcher

By Mark K. Sogge, U.S. Geological Survey; Darrell Ahlers, Bureau of Reclamation; and Susan J. Sferra, 

U.S. Fish and Wildlife Service

Chapter 10 of

Section A, Biological Science

Book 2, Collection of Environmental Data

Prepared in cooperation with the Bureau of Reclamation and the 

U.S. Fish and Wildlife Service

Techniques and Methods 2A-10

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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Suggested citation:

Sogge, M.K., Ahlers, Darrell, and Sferra, S.J., 2010, A natural history summary and survey protocol for the 

southwestern willow flycatcher: U.S. Geological Survey Techniques and Methods 2A-10, 38 p.
iii

Contents

Background.....................................................................................................................................................1

Section 1. Natural History............................................................................................................................2

Breeding Range and Taxonomy..........................................................................................................2

Migration and Winter Range, Habitat, and Ecology .......................................................................2

Breeding Habitat...................................................................................................................................4

Breeding Chronology and Biology ...................................................................................................11

Nests and Eggs....................................................................................................................................12

Food and Foraging ..............................................................................................................................13

Site Fidelity and Survivorship ...........................................................................................................13

Threats to the Flycatcher and Habitat.............................................................................................14

Section 2. Survey Protocol.........................................................................................................................16

Permits..................................................................................................................................................17

Pre-Survey Preparation.....................................................................................................................17

Equipment ............................................................................................................................................18

Willow Flycatcher Identification ......................................................................................................19

Timing and Number of Visits .............................................................................................................20

Survey Methods..................................................................................................................................22

Special Considerations......................................................................................................................25

Acknowledgments.......................................................................................................................................26

References Cited..........................................................................................................................................26

Appendix 1. Willow Flycatcher Survey and Detection Form ...............................................................31

Appendix 2. Willow Flycatcher Survey Continuation Sheet / Territory Summary Table .................33

Appendix 3. Instructions for Completing the Willow Flycatcher Survey and 

Detection Form and the Survey Continuation Sheet ................................................................34

Appendix 4. Example of a Completed Willow Flycatcher Survey and 

Detection Form (with map) ...........................................................................................................36
iv

Figures

Figure 1. Map showing approximate ranges of the Willow Flycatcher (Empidonax traillii)

during breeding and non-breeding seasons ............................................. 3

Figure 2. Photographs showing examples of Southwestern Willow Flycatcher breeding

habitat in native broadleaf vegetation at high-elevation sites ........................ 5

Figure 3. Photographs showing examples of Southwestern Willow Flycatcher breeding

habitat in native broadleaf vegetation at low and mid-elevation sites ............... 6

Figure 4. Photographs showing examples of Southwestern Willow Flycatcher breeding

habitat in exotic vegetation ............................................................... 7

Figure 5. Photographs showing examples of Southwestern Willow Flycatcher breeding

habitat in mixed native/exotic vegetation ................................................ 8

Figure 6. Photographs showing examples of dense vegetation structure within breeding

habitats of Southwestern Willow Flycatcher............................................. 9

Figure 7. Photographs showing examples of the variable hydrologic conditions at

breeding habitats of Southwestern Willow Flycatcher ................................. 10

Figure 8. Diagram showing generalized migration and breeding chronology for the

Willow Flycatcher in the Southwest ...................................................... 11

Figure 9. Diagram showing recommended numbers and timing of visits during each

survey period for general surveys and project surveys................................. 21

Conversion Factors

Multiply By To obtain

centimeter (cm) 0.3937 inch (in.)

gram (g) 0.03527 ounce, avoirdupois (oz)

hectare (ha) 2.471 acre

kilometer (km) 0.6214 mile (mi)

meter (m) 3.281 foot (ft)

millimeter (mm) 0.03937 inch (in.)

Abbreviations and Acronyms

GPS Global Positioning System

NDVI Normalized Difference Vegetation Index

USFWS U.S. Fish and Wildlife Service

USGS U.S. Geological Survey
A Natural History Summary and Survey Protocol for the 

Southwestern Willow Flycatcher 

By Mark K. Sogge, U.S. Geological Survey; Darrell Ahlers, Bureau of Reclamation; and 

Susan J. Sferra, U.S. Fish and Wildlife Service

Background

The Southwestern Willow Flycatcher (Empidonax 

traillii extimus) has been the subject of substantial research, 

monitoring, and management activity since it was listed as 

an endangered species in 1995. When proposed for listing 

in 1993, relatively little was known about the flycatcher’s 

natural history, and there were only 30 known breeding 

sites supporting an estimated 111 territories rangewide 

(Sogge and others, 2003a). Since that time, thousands of 

presence/absences surveys have been conducted throughout 

the historical range of the flycatcher, and many studies 

of its natural history and ecology have been completed. 

As a result, the ecology of the flycatcher is much better 

understood than it was just over a decade ago. In addition, 

we have learned that the current status of the flycatcher is 

better than originally thought: as of 2007, the population was 

estimated at approximately 1,300 territories distributed among 

approximately 280 breeding sites (Durst and others, 2008a).

Concern about the Southwestern Willow Flycatcher on 

a rangewide scale was brought to focus by Unitt (1987), who 

described declines in flycatcher abundance and distribution 

throughout the Southwest. E. t. extimus populations declined 

during the 20th century, primarily because of habitat loss and 

modification from activities, such as dam construction and 

operation, groundwater pumping, water diversions, and flood 

control. In 1991, the U.S. Fish and Wildlife Service (USFWS) 

designated the Southwestern Willow Flycatcher as a candidate 

category 1 species (U.S. Fish and Wildlife Service, 1991). 

In July 1993, the USFWS proposed to list E. t. extimus as an 

endangered species and to designate critical habitat under the 

Act (U.S. Fish and Wildlife Service, 1993). A final rule listing 

E. t. extimus as endangered was published in February 1995 

(U.S. Fish and Wildlife Service, 1995); critical habitat was 

designated in 1997 (U.S. Fish and Wildlife Service, 1997). 

The USFWS Service released a Recovery Plan for the 

Southwestern Willow Flycatcher in 2002 (U.S. Fish and 

Wildlife Service, 2002), and re-designated critical habitat in 

2005 (U.S. Fish and Wildlife Service, 2005). 

In addition to its federal status, the Southwestern Willow 

Flycatcher is listed as an endangered species or species of 

concern in Arizona (Arizona Game and Fish Department, 

2006), New Mexico (New Mexico Department of Game and 

Fish, 1996), California (California Department of Fish and 

Game, 1991), and Utah (Utah Division of Wildlife Resources, 

1997). 

Sound management and conservation of an endangered 

species like the Southwestern Willow Flycatcher requires 

current, detailed information on its abundance and 

distribution. This requires, among other things, identifying 

where flycatchers are and are not breeding, and annual 

monitoring of as many breeding areas as possible. Such efforts 

require effective, standardized survey protocols and consistent 

reporting, at both local and regional levels. However, the 

Willow Flycatcher is a difficult species to identify and survey 

for. Moreover, inconsistent or ineffective surveys are of 

limited value, can produce misleading information (including 

“false positives” and “false negatives”), hinder regional and 

rangewide analyses, and waste limited resources.

We developed this document to provide a standardized 

survey protocol and a source of basic ecological and status 

information on the flycatcher. The first section summarizes the 

current state of knowledge regarding Southwestern Willow 

Flycatcher natural history, based on a wide array of published 

and unpublished literature. Emphasis is given to information 

relevant to flycatcher conservation and management, and 

to conducting and interpreting surveys. The second section 

details a standard survey protocol that provides for consistent 

data collection, reporting, and interpretation. This protocol 

document builds on and supersedes previous versions, the 

most recent of which was Sogge and others (1997a). In this 

update, we incorporate over a decade of new science and 

survey results, and refine the survey methodology to clarify 

key points. Further, we update the standard survey data 

sheets and provide guidelines on how to fill in the requested 

information. Amidst these revisions, the basic approach of the 

survey protocol has remained unchanged—multiple surveys 

at each survey area within the same breeding season, the use 

of the call-playback technique using flycatcher vocalizations 

to increase the probability of detection, and verification of 

species identity through its diagnostic song. 
2 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

Section 1. Natural History

Breeding Range and Taxonomy

The Willow Flycatcher is a widespread species that 

breeds across much of the conterminous United States 

(Sedgwick, 2000). Four subspecies commonly are recognized 

in North America, with each occupying a distinct breeding 

range (fig. 1): E. t. adastus, ranging across the northern Rocky 

Mountains and Great Basin; E. t. brewsteri, found west of 

the Sierra Nevada and Cascade Mountains along the Pacific 

Slope; E. t. extimus, the Southwestern Willow Flycatcher, 

which breeds across the Southwest; and E. t. traillii, ranging 

east of the northern Rocky Mountains. Although the overall 

subspecies’ ranges are distinct, Sedgwick (2001) and Paxton 

(2008) noted interbreeding/gradation zones in the boundary 

area between E. t. extimus and E. t. adastus.

The breeding range of the Southwestern Willow 

Flycatcher includes southern California, Arizona, New 

Mexico, southwestern Colorado, and extreme southern 

portions of Nevada and Utah: specific range boundaries are 

delineated in the subspecies’ recovery plan (U.S. Fish and 

Wildlife Service, 2002). Unitt (1987) included western Texas 

in the subspecies’ range, but recent breeding records from 

western Texas are lacking. Records of probable breeding 

Southwestern Willow Flycatchers in Mexico are few and 

restricted to extreme northern Baja California and Sonora 

(Unitt, 1987; Wilbur, 1987). Although recent data are lacking, 

the USFWS does include parts of northern Mexico in its 

description of E. t. extimus breeding range (U.S. Fish and 

Wildlife Service, 2002). 

Although they appear very similar to most observers, 

experienced taxonomist or those using specialized equipment 

(for example, an electronic colorimeter) can differentiate 

among the subspecies by subtle differences in color and 

morphology (for example, Unitt, 1987; Paxton, 2008). 

Despite the subtle level of differences, the taxonomic status 

of E. t. extimus has been critically reviewed and confirmed 

multiple times based on morphological, genetic, and song data 

(Hubbard, 1987; Unitt, 1987; Browning, 1993; Paxton, 2000; 

Sedgwick, 2001). 

The Southwestern Willow Flycatcher was described by 

Phillips (1948) from a specimen collected along the San Pedro 

River in southeastern Arizona. The Southwestern Willow 

Flycatcher generally is paler than other Willow Flycatcher 

subspecies, although this difference is indistinguishable 

without considerable experience and training, and study 

skins as comparative reference material. The southwestern 

subspecies differs in morphology (primarily wing formula) but 

not overall size. The plumage and color differences between 

the Willow Flycatcher subspecies are so subtle that they 

should not be used to characterize birds observed in the field 

(Unitt, 1987; Hubbard, 1999; U.S. Fish and Wildlife Service, 

2002).

Migration and Winter Range, Habitat, and 

Ecology

All Willow Flycatcher subspecies breed in North America 

but winter in the subtropical and tropical regions of southern 

Mexico, Central America, and northern South America 

(Sedgwick, 2000; Koronkiewicz, 2002; fig. 1). Most wintering 

birds are found in the Pacific slope lowlands in Mexico and 

Central America, and Caribbean slope lowlands in Mexico and 

Guatemala.

Because all Willow Flycatcher subspecies look 

very similar, determining specific wintering sites for the 

southwestern race has been challenging. However, recent 

genetic analysis of wintering birds (Paxton, 2008) suggests 

that the four subspecies occupy finite areas of the wintering 

grounds, but with overlapping ranges. The Southwestern 

Willow Flycatcher appears to be largely restricted to the center 

of the winter range (in the vicinity of Costa Rica), although 

Paxton (2008) suggests more research is needed to address this 

question. 

On the wintering grounds, flycatchers primarily are found 

in habitats that have four main components: (1) standing 

or slow moving water and/or saturated soils, (2) patches 

or stringers of trees, (3) woody shrubs, and (4) open areas 

(Koronkiewicz and Whitfield, 1999; Koronkiewicz and 

Sogge, 2000; Lynn and others, 2003; Nishida and Whitfield, 

2007; Schuetz and others, 2007). Based on surveys to date, 

the presence of water or saturated soils is almost universal, 

although tree heights and configurations, the presence of 

woody shrubs, and the amount of open space surrounding 

winter territories can vary considerably (Schuetz and others, 

2007).

Male and female flycatchers hold separate, individual 

non-breeding territories, and defend those territories 

throughout the winter by using song, calls, and aggression 

displays. Fidelity to wintering territories and sites is high, as 

is survivorship over the wintering period (Koronkiewicz and 

others, 2006b; Sogge and others, 2007).

Willow Flycatchers travel approximately 1,500–8,000 km 

each way between wintering and breeding areas. During 

migration, flycatchers use a wider array of forest and 

shrub habitats than they do for breeding, although riparian 

vegetation may still be a preferred migration habitat type 

(Finch and others, 2000). Migration requires high energy 

expenditures, exposure to predators, and successful foraging in 

unfamiliar areas. Therefore, migration is the period of highest 

mortality within the annual cycle of the flycatcher (Paxton and 

others, 2007). Willow Flycatchers of all subspecies sing during 

northward migration, perhaps to establish temporary territories 

for short-term defense of food resources.
Section 1. Natural History 3

Figure 1. Approximate ranges of the Willow Flycatcher (Empidonax traillii) during breeding and non-breeding seasons.

tac10-0495_fig01

E. t. traillii

E. t. adastus

E. t. extimus

E. t. brewsteri

Ecuador

Guyana

Cuba

Suriname

Nicaragua

Honduras

Guatemala

Panama

Haiti

French

Guiana

Costa

Rica

Belize

Dominican

Republic

El Salvador

Jamaica Puerto

Rico

United States of America

Mexico

Canada

Brazil

Peru

Colombia

Venezuela

Gulf of Mexico Pacific

Ocean

Atlantic Ocean

EXPLANATION

130° 120° 110° 100° 90° 80° 70° 60° 50°

50°

40°

30°

20°

10°

0°

Basemap modified from U.S. Geological Survey and other agency 

digital data, various scales. Projection Mercator, World Geodetic 

System1984 datum.

0 1,000 Miles

0 1,000 Kilometers

Approximate range distribution of the Willow Flycatcher (Empidonax 

traillii)—Adapted from Unitt (1987), Browning (1993), and Paxton (2008)

Breeding range, including boundaries of the Willow Flycatcher subspecies

? Wintering range—Question marks reflect uncertainty of 

the location of the eastern boundary of the winter range

?

?

?
4 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

Southwestern Willow Flycatchers typically arrive on 

breeding grounds between early May and early June (Ellis and 

others, 2008; Moore and Ahlers, 2009). Because arrival dates 

vary annually and geographically, northbound migrant Willow 

Flycatchers of multiple subspecies pass through areas where 

Southwestern Willow Flycatchers have already begun nesting. 

Similarly, southbound migrants in late July and August 

may occur where Southwestern Willow Flycatchers are still 

breeding (Unitt, 1987). This can make it challenging for an 

observer to differentiate local breeders from migrants. Other 

than timing, we still know relatively little about Southwestern 

Willow Flycatcher migratory behavior, pathways, or habitat 

use. 

Breeding Habitat

Breeding Southwestern Willow Flycatchers are riparian 

obligates, typically nesting in relatively dense riparian 

vegetation where surface water is present or soil moisture 

is high enough to maintain the appropriate vegetation 

characteristics (Sogge and Marshall, 2000; U.S. Fish and 

Wildlife Service, 2002; Ahlers and Moore, 2009). However, 

hydrological conditions in the Southwest can be highly 

variable within a season and between years, so water 

availability at a site may range from flooded to dry over the 

course of a breeding season or from year to year.

The Southwestern Willow Flycatcher breeds in dense 

riparian habitats across a wide elevational range, from near 

sea level in California to more than 2,600 m in Arizona and 

southwestern Colorado (Durst and others, 2008a). Vegetation 

characteristics of Southwestern Willow Flycatcher breeding 

habitat generally include dense tree or shrub cover that is 

≥ 3 m tall (with or without a higher overstory layer), dense 

twig structure, and high levels of live green foliage (Allison 

and others, 2003); many patches with tall canopy vegetation 

also include dense midstory vegetation in the 2–5 m range. 

Beyond these generalities, the flycatcher shows adaptability in 

habitat selection, as demonstrated by variability in dominant 

plant species (both native and exotic), size and shape of 

breeding patch, and canopy height and structure (U.S. Fish and 

Wildlife Service, 2002). 

Southwestern Willow Flycatcher breeding habitat can be 

quantified and characterized in a number of ways, depending 

on the level of detail needed and habitat traits of interest. For 

many sites, detailed floristic composition, plant structure, 

patch size, and even characteristics such as Normalized 

Difference Vegetation Index (NDVI) have been described 

in agency reports and scientific journal articles (Allison and 

others, 2003; Hatten and Paradzick, 2003; Koronkiewicz and 

others, 2006a; Hatten and Sogge, 2007; Moore, 2007; Schuetz 

and Whitfield, 2007; Ellis and others, 2008). For purposes of 

this survey protocol, we take a relatively simple approach and 

broadly describe and classify breeding sites based on plant 

species composition and habitat structure. Clearly, these are 

not the only important components, but they are conspicuous 

to human perception and easily observed and recorded. Thus, 

they have proven useful in conceptualizing, selecting and 

evaluating suitable survey habitat, and in predicting where 

breeding flycatchers are likely to be found. 

Breeding habitat types commonly used by Southwestern 

Willow Flycatchers are described below. The general 

categories are based on the composition of the tree/shrub 

vegetation at the site—native broadleaf, exotic, and mixed 

native/exotic. In the field, breeding habitats occur along 

a continuum of plant species composition (from nearly 

monotypic to mixed species) and vegetation structure (from 

simple, single stratum patches to complex, multiple strata 

patches). The images in figures 2–7 illustrate some of the 

variation in flycatcher breeding habitat, and other examples 

can be found in numerous publications and agency reports, 

and on the USGS photo gallery web site (http://sbsc.wr.usgs.

gov/SBSCgallery/). The intent of the descriptions and 

photographs is to provide a general guide for identifying 

suitable habitat in which to conduct surveys.

Native broadleaf.—Southwestern Willow Flycatchers 

breed across a great elevational range, and the characteristics 

of their native broadleaf breeding sites varies between high 

elevation sites and those at low and mid-elevation sites. 

High elevation sites (fig. 2) range from nearly monotypic 

dense stands of willow to mixed stands of native broadleaf 

trees and shrubs, 2–7 m in height with no distinct overstory 

layer; often associated with sedges, rushes, nettles, and other 

herbaceous wetland plants; usually very dense structure in 

lower 2 m; live foliage density is high from the ground to the 

canopy. Vegetation surrounding the patch can range from open 

meadow, to agricultural lands, to pines or upland shrub.

At low and mid-elevations (fig. 3), flycatcher breeding 

sites can be composed of single species (often Goodding’s 

willow (Salix gooddingii), S. exigua, or other willow species) 

or mixtures of native broadleaf trees and shrubs including (but 

not limited to) cottonwood, willows, boxelder (Acer negundo), 

ash (Fraxinus spp.), alder (Alnus spp.), and buttonbush 

(Cephalanthus spp.), height from 3 to 15 m; characterized 

by trees of different size classes; often a distinct overstory of 

cottonwood, willow or other broadleaf tree, with recognizable 

subcanopy layers and a dense understory of mixed species; 

exotic/introduced species may be a rare component, 

particularly in the understory.

Monotypic exotic.—(fig. 4) Breeding sites also can 

include nearly monotypic, dense stands of exotics such 

as saltcedar (Tamarix spp.) or Russian olive (Elaeagnus 

angustifolia), 4–10 m in height forming a nearly continuous, 

closed canopy (with no distinct overstory layer); lower 2 m 

commonly very difficult to penetrate due to dense branches, 

however, live foliage density may be relatively low 1–2 m 

above ground, but increases higher in the canopy; canopy 

density uniformly high.
Section 1. Natural History 5

Figure 2. Examples of Southwestern Willow Flycatcher breeding habitat in native broadleaf vegetation at 

high-elevation sites. 

Little Colorado River near Greer, Arizona. Photograph 

courtesy of Arizona Game and Fish Department, 1996.

Aerial view of Little Colorado River near Greer, Arizona. Photograph by 

USGS, 1995.

McIntyre Springs, Colorado. Photograph by USGS, 2002.

Rio Grande State Wildlife Area, Colorado. Photograph by USGS, 2002.

Parkview Fish Hatchery, New Mexico. Photograph by USGS, 2000.

Tierra Azul, New Mexico. Photograph by USGS, 2005.
6 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

Hassayampa River, Arizona. Photograph by USGS, 2003.

Figure 3. Examples of Southwestern Willow Flycatcher breeding habitat in native broadleaf vegetation at low and mid-elevation sites.

Santa Ynez River, California, Photograph by USGS, 1996. 

Bosque del Apache, Rio Grande, New Mexico. Photograph courtesy of Bureau 

of Reclamation, 2008.

Kern River, California. Photograph by USGS, 1995.

Kern River, California. Photograph by USGS, 1995. 

San Luis Rey River, California. Photograph by USGS, 2005.
Section 1. Natural History 7

Salt River, Arizona. Photograph courtesy of Bureau of Reclamation, 1996.

Aerial view of Topock Marsh, Colorado River, Arizona. Photograph by USGS, 

1996.

Topock Marsh, Colorado River, Arizona. Photograph by USGS, 1996.

Rio Grande, New Mexico. Photograph by USGS, 2005.

Orrilla Verde, Rio Grande, New Mexico. Photograph by USGS, 2006.

Aerial view of Salt River, Arizona. Photograph by USGS, 1996.

Figure 4. Examples of Southwestern Willow Flycatcher breeding 

habitat in exotic vegetation.
8 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

Mixed native/exotic—(fig. 5) These sites include dense 

mixtures of native broadleaf trees and shrubs (such as those 

listed above) mixed with exotic/introduced species, such 

as saltcedar or Russian olive; exotics are often primarily in 

the understory, but may be a component of overstory; the 

native and exotic components may be dispersed throughout 

the habitat or concentrated as a distinct patch within a larger 

matrix of habitat; overall, a particular site may be dominated 

primarily by natives or exotics, or be a more-or-less equal 

mixture. 

Regardless of the plant species composition or height, 

occupied sites almost always have dense vegetation in 

the patch interior (fig. 6). These dense patches are often 

interspersed with small openings, open water, or shorter/

sparser vegetation, creating a mosaic that is not uniformly 

dense.

Gila River, Arizona. Photograph by USGS, 2002. Roosevelt Lake, Arizona. Photograph by USGS, 1999.

Verde River River, Arizona. Photograph by USGS, 2002. Virgin River, Utah. Photograph by USGS, 1997.

Figure 5. Examples of Southwestern Willow Flycatcher breeding habitat in mixed native/exotic vegetation.
Section 1. Natural History 9

Gila River, Arizona. Photograph by USGS, 2002. Kern River, California. Photograph by USGS, 1999.

Rio Grande, New Mexico. Photograph by USGS, 2007. Salt River, Arizona. Photograph by USGS, 1999.

Rio Grande, New Mexico. Photograph by USGS, 2005.

Rio Grande, New Mexico. Photograph by USGS, 2007.

Figure 6. Examples of dense vegetation structure within breeding habitats of Southwestern Willow Flycatcher.
10 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

Riparian patches used by breeding flycatchers vary in 

size and shape, ranging from a relatively contiguous stand of 

uniform vegetation to an irregularly shaped mosaic of dense 

vegetation with open areas. Southwestern Willow Flycatchers 

have nested in patches as small as 0.8 ha (for example, in 

the Grand Canyon) and as large as several hundred hectares 

(for example, at Roosevelt Lake, Ariz., or Elephant Butte 

Reservoir, New Mex.). They have only rarely been found 

nesting in isolated, narrow, linear riparian habitats that are less 

than 10 m wide, although they will use such linear habitats 

during migration.

Flycatcher territories and nests typically are adjacent 

to open water, cienegas, marshy seeps, or saturated soil, and 

within riparian areas rooted in standing water. However, in 

the Southwest, hydrological conditions at a site can vary 

remarkably within a season, between years, and among nearby 

sites (fig. 7). Surface water or saturated soil may only be 

present early in the breeding season (that is, May and part 

of June), especially in dry years. Similarly, vegetation at a 

patch may be immersed in standing water during a wet year, 

but be hundreds of meters from surface water in dry years 

(Ahlers and Moore, 2009). This is particularly true of reservoir 

sites, such as the Kern River at Lake Isabella, Calif., Tonto 

Creek and Salt River at Roosevelt Lake, and the Rio Grande 

near Elephant Butte Reservoir. Natural or human-caused 

river channel modifications and altered subsurface flows (for 

example, from agricultural runoff), can lead to a total absence 

of water or visibly saturated soil at a site for several years. 

Other potentially important aspects of Southwestern 

Willow Flycatcher habitat include distribution and isolation 

of vegetation patches, hydrology, food base (arthropods), 

parasites, predators, environmental factors (for example 

temperature, humidity), and interspecific competition (U.S. 

Fish and Wildlife Service, 2002). Population dynamics 

Rio Grande at San Marcial, New Mexico, with flowing water beneath the 

territories. Photograph by USGS, 2007.

Rio Grande at San Marcial, New Mexico, with dry substrate. Photograph by 

USGS, 2007.

Tonto Creek inflow to Roosevelt Lake, Arizona, during a dry year. Photograph 

by USGS, 2004.

Figure 7. Examples of the variable hydrologic conditions at breeding habitats of Southwestern Willow Flycatcher.

Tonto Creek inflow to Roosevelt Lake, Arizona, during high-water year. 

Photograph by USGS, 2005.
Section 1. Natural History 11

factors, such as demography (for example, survivorship 

rates, fecundity), distribution of breeding groups across the 

landscape, flycatcher dispersal patterns, migration routes, 

the tendency for adults and surviving young to return to their 

previous year breeding site, and conspecific sociality also 

influence where flycatchers are found and what habitats they 

use (U.S. Fish and Wildlife Service, 2002). 

It is critically important to recognize that the ultimate 

measure of habitat suitability is not simply whether or not a 

site is occupied. Habitat suitability occurs along a gradient 

from high to poor to unsuitable; the best habitats are those in 

which flycatcher reproductive success and survivorship result 

in a stable or growing population. Some occupied habitats 

may be acting as population sources, while others may be 

functioning as population sinks (Pulliam, 1988). Therefore, 

it can take extensive research to determine the quality of any 

given habitat patch. Furthermore, productivity and survival 

rates can vary widely among years (Paxton and others, 

2007; Ellis and others, 2008; Ahlers and Moore, 2009), so 

conclusions based on short-term datasets or data extrapolated 

from one area to another may be erroneous. It also is important 

to note that not all unoccupied habitat is unsuitable; some sites 

with suitable habitat may be geographically isolated or newly 

established, such that they are not yet colonized by breeding 

flycatchers. There also may simply not be enough flycatchers 

in a given area to fill all available habitat in particular 

locations (U.S. Fish and Wildlife Service, 2002). A better 

understanding of which habitats or sites are sinks or sources 

can be especially helpful in site conservation and restoration 

planning.

As described earlier, migrant Willow Flycatchers may 

occur in riparian habitats that are structurally unsuitable for 

breeding (for example, too sparse, smaller patch size, etc.), 

and in non-riparian habitats. Such migration stopover areas, 

even though not used for breeding, may be critically important 

resources affecting local and regional flycatcher productivity 

and survival (U.S. Fish and Wildlife Service, 2002, 2005).

Breeding Chronology and Biology

Unless otherwise noted, the information that follows 

and upon which the generalized breeding season chronology 

(fig. 8) is based comes from Unitt (1987), Whitfield (1990), 

Maynard (1995), Sogge and others (2003b), Paxton and others 

(2007), Schuetz and Whitfield (2007), and Ellis and others 

(2008). Extreme or record dates for any stage of the breeding 

cycle may vary by 1–2 weeks from the dates presented, 

depending on the geographic area, extreme weather events, 

yearly variation and other factors. Higher elevation areas, in 

particular, have delayed chronology (Ahlers and White, 2000).

Figure 8. Generalized migration and breeding chronology for the Willow Flycatcher in the Southwest. 

Extreme or record dates may occur slightly earlier or later than indicated.

Generalized Breeding Season Chronology 

Arrival on Territories

Nest Building 

Eggs and Incubation

Chicks in Nest

Fledging from Nest

? Depart Sites ?

Northbound Migration Southbound Migration 

April May June July August September
12 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

Both sexes can breed beginning in their second year. 

Male Southwestern Willow Flycatchers generally arrive 

at breeding areas first; older males typically arrive before 

younger ones. Although females usually arrive a few weeks 

after males, some older females are present at sites before 

late-arriving males. Adult flycatchers will sometimes wander 

extensively through large riparian sites before and after 

breeding, possibly as a way to evaluate potential breeding 

habitat (Cardinal and others, 2006). 

Males establish and defend their territories through 

singing and aggressive interactions. Females settle on 

established territories, and may choose a territory more for its 

habitat characteristics than for the traits of its territorial male. 

Territory size tends to be larger when a male first arrives, then 

gets smaller after a female pairs with the male (Cardinal and 

others, 2006). Similarly, male song rate is very high early 

in the season, then declines after pairing (Yard and Brown, 

2003). Not all males are successful in attracting mates in a 

given year, and as a result unpaired territorial males occur 

at many breeding sites. Unpaired males are usually a small 

percentage of any local population, but can comprise as 

much as 15–25 percent of the territories in some populations 

(Munzer and others, 2005; Ahlers and Moore, 2009).

Although the Willow Flycatcher as a species is 

considered predominantly monogamous during the breeding 

season (Sedgwick, 2000), some Southwestern Willow 

Flycatcher populations have a relatively high degree of 

polygyny whereby one male can have more than one breeding 

female in its territory. Polygynous males generally have two 

females in their territory, but up to four have been recorded 

(Davidson and Allison, 2003; Pearson and others, 2006). 

Polygyny rates can vary between sites, and among years at a 

given site. At some sites, polygynous males have much higher 

productivity than monogamous males (Paxton and others, 

2007).

Nest building within the territory usually begins within a 

week or two after pair formation. Egg laying begins as early 

as mid-May, but more often starts in late May to mid-June. 

Chicks can be present in nests from late May through early 

August. Young typically fledge from nests from mid-June 

through mid-August; later fledglings are often products of 

re-nesting attempts. Breeding adults generally depart from 

their territories in early to mid-August, but may stay later 

if they fledged young late in the season. Males that fail to 

attract or retain mates, and males or pairs that are subject 

to significant disturbance, such as repeated nest parasitism 

or predation may leave territories by early July. Fledglings 

probably leave the breeding areas a week or two after adults, 

but few details are known.

Southwestern Willow Flycatcher territory size varies 

widely, probably due to differences in population density, 

habitat quality (including vegetation density and food 

availability), and nesting stage. Studies have reported 

estimated territory sizes ranging from 0.06 to 2.3 ha (Sogge 

and others, 1995; Whitfield and Enos, 1996; Bureau of 

Reclamation, 2009). At Roosevelt Lake, Ariz., measurements 

of home ranges, which include the defended territory and 

sometimes adjacent use areas, averaged 0.4 ha for actively 

breeding males; home range can be much larger for preand post-breeding males (Paxton and others, 2007). During 

incubation and nestling phases territory size, or at least the 

activity centers of pairs, can be very small. Flycatchers may 

increase their activity area after young are fledged, and use 

non-riparian habitats adjacent to the breeding area (Cardinal 

and others, 2006). This variability among sites, individual 

territories, and over time illustrates the challenge of defining 

a minimum habitat patch size for breeding flycatchers, or 

estimating the number of territories based simply on the size 

of a given breeding site.

At some breeding sites, non-territorial adult “floaters” 

will be present among the territorial population. Floaters are 

quieter and less aggressive than territorial adults, and therefore 

are harder to detect and frequently overlooked. Most floaters 

are young males, and float for only a single year. At Roosevelt 

Lake, floaters typically accounted for 3–8 percent of the 

known adult population, although the rate was much higher 

in drought years when habitat quality was lower (Paxton 

and others, 2007). The presence of floaters in a population 

may indicate that there is not enough high quality habitat to 

support all potentially territorial individuals present in a given 

breeding season. 

Nests and Eggs

Historically, 75–80 percent of reported Southwestern 

Willow Flycatcher nests were placed in willows (Phillips, 

1948; Phillips and others, 1964; Hubbard, 1987; Unitt, 1987). 

Southwestern Willow Flycatchers still commonly place their 

nests in native plants, but will often build nests in exotics, 

such as saltcedar and Russian olive (Sogge and Marshall, 

2000; Stoleson and Finch, 2003; Durst and others, 2008a). 

In Arizona, most nests are in saltcedar or willows (Paradzick 

and Woodward, 2003; McLeod and others, 2007). In a unique 

situation in San Diego County, Calif., the flycatcher nests in 

coast live oak (Quercus agrifolia) along the San Luis Rey 

River (Haas, 2003), where oak became the dominant plant 

species adjacent to the river following willow removal in 

the 1950s. In another unusual situation, flycatchers in the 

Cliff-Gila Valley in New Mex. nest in tall boxelder (Stoleson 

and Finch, 2003). Southwestern Willow Flycatcher nests also 

have been found in buttonbush, black twinberry (Lonicera 

involucrata), Fremont cottonwood (Populus fremontii), alder 

(Alnus spp.), blackberry (Rubus ursinus), baccharis (Baccharis

spp.), and stinging nettle (Urtica spp.). Overall, flycatcher nest 

site selection appears to be driven more by plant structure than 

by species composition.
Section 1. Natural History 13

Southwestern Willow Flycatchers build open cup nests 

approximately 8 cm high and 8 cm wide (outside dimensions), 

exclusive of any dangling material at the bottom. Females 

build the nest with little or no assistance from the males. 

Nests typically are placed in the fork of a branch with the 

nest cup supported by several small-diameter vertical stems. 

Nest height is highly variable and depends on the available 

plant structure within the territory; nests have been found 

from 0.6 m to approximately 20 m above ground. In any given 

habitat type or nest substrate, nests can be placed wherever 

suitable twig structure and vegetative cover are present.

Egg laying generally begins from mid-May through 

mid-June, depending on the geographic area and elevation. 

Willow Flycatcher eggs are buffy or light tan, approximately 

18 mm long and 14 mm wide, with brown markings in a 

wreath at the blunt end. Clutch size is usually three or four 

eggs for first nests. Only the female develops a brood patch 

and incubates the eggs. Incubation lasts 12–13 days from the 

date the last egg is laid, and all eggs typically hatch within 

24–48 hours of each other. 

Flycatcher chicks are altricial and weigh only about 1–2 

g at hatching, but grow rapidly and are ready to leave the nest 

at 12–15 days of age (Sedgwick, 2000; Paxton and Owen, 

2002). The female provides most or all initial care of the 

young, although the role of the male increases with the age 

and size of nestlings. After Willow Flycatchers fledge at 12–15 

days of age, they stay close to the nest and each other for 

3–5 days, and adults continue feeding the fledged young for 

approximately 2 weeks. Recently fledged birds may repeatedly 

return to and leave the nest during this period (Spencer and 

others, 1996). Both male and female adults feed the fledged 

young, which give frequent, loud “peep” calls.

Southwestern Willow Flycatchers readily re-nest 

following an unsuccessful nesting attempt, although rarely 

more than once (Ellis and others, 2008). They also will 

sometimes nest again (double brood) following a successful 

nesting attempt, although this is more uncommon than 

re-nesting and varies between sites and years. From 2002 to 

2008 at Elephant Butte Reservoir, approximately 13 percent 

of the pairs produced two successful nests per year (Ahlers 

and Moore, 2009). The productivity gains from pairs having 

successful second nests are important drivers of positive 

population growth (Paxton and others, 2007; Moore and 

Ahlers, 2009). 

Replacement nests are built in the same territory, either 

in the same plant or at a distance of as much as 20 m from 

the previous nest. Reuse of old nests is uncommon, but does 

occur (Yard and Brown, 1999; Darrell Ahlers, Bureau of 

Reclamation, unpub. data, 2009). Replacement nest building 

and egg laying can occur (uncommonly) as late as the end 

of July or early August. Pairs may attempt a third nest if the 

second fails. However, clutch size, and therefore potential 

productivity, decreases with each nest attempt (Whitfield and 

Strong, 1995; Ellis and others, 2008).

Food and Foraging

The breeding season diet of Southwestern Willow 

Flycatchers is relatively well documented (DeLay and others, 

2002; Drost and others, 2003; Durst, 2004; Wiesenborn and 

Heydon, 2007; Durst and others, 2008b). Breeding flycatchers 

are exclusively insectivorous, and consume a wide range of 

prey taxa ranging in size from small leafhoppers (Homoptera) 

to large dragonflies (Odonata). Major prey taxa include bugs 

(Hemiptera), bees and wasps (Hymenoptera), flies (Diptera), 

and leafhoppers; however, diet can vary widely between 

years and among different habitat types. There is no known 

differences in diet by sex, but there are differences between 

adult and nestling diet in the proportions of some arthropod 

groups. Differences in the composition of arthropods in 

flycatcher diet have been documented between native and 

exotic habitats, and between years within particular breeding 

sites; however, flycatchers appear able to tolerate substantial 

variation in relative prey abundance, except in extreme 

situations such as severe droughts (Durst and others, 2008b).

Willow Flycatchers of all subspecies forage primarily by 

sallying from a perch to perform aerial hawking and gleaning 

(Sedgwick, 2000; Durst, 2004). Males and females forage with 

similar maneuvers, although males may forage higher in the 

tree canopy than females. Foraging frequently takes place at 

external edges or internal openings within a habitat patch, or at 

the top of the upper canopy. 

Site Fidelity and Survivorship

Based on studies of banded birds, most adult 

Southwestern Willow Flycatchers that survive from one year 

to the next will return to the same river drainage, often in 

proximity to the same breeding site (U.S. Fish and Wildlife 

Service, 2002; McLeod and others, 2007; Paxton and others, 

2007). However, it is common for individual flycatchers to 

return to different sites within a breeding area, and even to 

move between breeding areas, from one year to the next. 

Some of this movement may be related to breeding success 

and habitat quality. At Roosevelt Lake, those birds that moved 

to different sites within a breeding area had on average higher 

productivity in the year following the move than in the year 

before the move (Paxton and others, 2007). At Roosevelt 

Lake and on the San Pedro and Gila Rivers, movement out 

of breeding patches also increased with the relative age of a 

patch, which may indicate a preference for younger riparian 

vegetation structure. 

In addition to movements within a breeding site, 

long-distance movements within and between drainages have 

been observed (Paxton and others, 2007), at distances up to 

approximately 450 km. Dispersal of first-year flycatchers 

is more extensive than adult birds, as typical for most bird 

species. 
14 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

Survivorship within the breeding season can be very 

high, averaging 97 percent at Roosevelt Lake (Paxton and 

others, 2007). Between-year survivorship of adults can be 

highly variable, but appears to be similar to that of most small 

passerine birds studied, with estimates generally ranging 

from approximately 55 to 65 percent (Stoleson and others, 

2000; McLeod and others, 2007; Paxton and others, 2007; 

Schuetz and Whitfield, 2007). Males and females have similar 

survivorship rates. 

Estimated survivorship of young birds (from hatching 

to the next breeding season) is highly variable, depending in 

part on how the estimates are generated (Stoleson and others, 

2000). Generally reported as between 15 and 40 percent, 

juvenile survivorship typically is lower than adult survivorship 

(Whitfield and Strong, 1995; Stoleson and others, 2000; 

McLeod and others, 2007). Early fledging young have higher 

survivorship than those that leave the nest later in the season 

(Whitfield and Strong, 1995; Paxton and others, 2007). Most 

flycatchers survive for only 1–2 adult years, and mean life 

expectancy in Arizona was estimated to be 1.9 years following 

fledging. However, some individuals live much longer. The 

maximum reported ages of banded Southwestern Willow 

Flycatchers are 9–11 years (Sedgwick, 2000; Paxton and 

others, 2007).

Overall, the Southwestern Willow Flycatcher population 

appears to persist as one or more widely dispersed 

metapopulations (Busch and others, 2000; U.S. Fish and 

Wildlife Service, 2002), with movement of individuals, 

and thus genetic exchange, occurring across the landscape. 

However, the amount of movement and interchange is lower 

among sites that are farther apart or more isolated. Some sites 

serve as population sources while others may be sinks; some 

sites will be ephemeral over periods of years or decades. 

Flycatcher movement and dispersal among sites is important 

for initial site colonization and subsequent recolonization. 

There are few general predictors for the persistence of 

breeding sites. Relatively large populations, such as the Kern 

River Preserve, San Pedro River, Elephant Butte Reservoir, 

and the Gila River have persisted for 10 or more years. 

However, such large sites can be subject to major changes 

in population numbers, and even potential extirpation, due 

to changes in local hydrology, site inundation, drought, etc. 

(Moore, 2005; Paxton and others, 2007). Although some small 

populations may be ephemeral and last only a few years (Durst 

and others, 2008a), others have remained occupied for much 

longer periods (Kus and others, 2003). Breeding populations 

also may reappear at unoccupied sites following 1–5 year 

absences. Suitable flycatcher habitat also can develop—and 

poor quality habitat can improve—relatively quickly in some 

sites, under favorable hydrological conditions. For example, 

at Roosevelt Lake and the San Pedro River (AZ), the age 

of riparian vegetation when first colonized was as young 

as 3 years (Paxton and others, 2007). In the same study, 

flycatchers moved back into older habitat patches when nearby 

younger, occupied habitat was inundated or scoured away. 

Overall, the vegetation and flycatcher occupancy of a 

habitat patch or river drainage are often dynamic; few if any 

sites remain static over time. The amount of suitable flycatcher 

habitat can substantially increase or decrease in just a few 

years, at local and regional scales. Flycatchers can respond 

quickly to habitat changes, colonizing new sites if available 

and abandoning others. Therefore, one cannot assume that 

local, regional, or rangewide flycatcher population numbers 

will remain stable over time. 

Threats to the Flycatcher and Habitat

The greatest historical factor in the decline of the 

Southwestern Willow Flycatcher is the extensive loss, 

fragmentation, and modification of riparian breeding habitat 

(U.S. Fish and Wildlife Service, 2002). Large-scale losses 

of southwestern wetlands have occurred, particularly the 

cottonwood-willow riparian habitats historically used by 

the Southwestern Willow Flycatcher (Unitt, 1987; General 

Accounting Office, 1988; Dahl, 1990; State of Arizona, 1990). 

Changes in the riparian plant community have frequently 

reduced, degraded, and eliminated nesting habitat for the 

flycatcher, curtailing its distribution and abundance. 

Habitat losses and changes have occurred and 

continue to occur because of urban, recreational, and 

agricultural development, water diversion and impoundment, 

channelization, livestock grazing, and replacement of native 

habitats by introduced plant species (Marshall and Stoleson, 

2000; U.S. Fish and Wildlife Service, 2002). Hydrological 

changes, natural or man-made, can greatly reduce the quality 

and extent of flycatcher habitat. Although riparian areas are 

often not considered as fire-prone, several Southwestern 

Willow Flycatcher breeding sites were destroyed by fire over 

the past decade (U.S. Fish and Wildlife Service, 2002), and 

others are at risk to similar catastrophic loss. Fire danger in 

these riparian systems may be exacerbated by increases in 

exotic vegetation, such as saltcedar, diversions or reductions of 

surface water, increased recreational activity, and drawdown 

of local water tables.

Although the degradation of many river systems and 

associated riparian habitat is a key cause of their absence, 

Southwestern Willow Flycatchers do not require free-running 

rivers or “pristine” riparian habitats. Most of the largest 
Section 1. Natural History 15

Southwestern Willow Flycatcher populations in the last 

decade were found in reservoir drawdown zones, such as at 

Roosevelt Lake and Elephant Butte Reservoir. Many breeding 

populations are found on regulated rivers (Graf and others, 

2002). In addition, the vegetation at many smaller flycatcher 

breeding sites is supported by artificial water sources such as 

irrigation canals, sewage outflow, or agricultural drainages 

(U.S. Fish and Wildlife Service, 2002). Although rising water 

levels could be detrimental to breeding flycatchers within a 

reservoir drawdown zone, reservoir fluctuations can simulate 

river dynamics with cycles of destruction and establishment of 

riparian vegetation, depositing rich sediments and flushing salt 

accumulations in the soil (Paxton and others, 2007). Therefore, 

managed and manipulated rivers and reservoirs have the 

potential to play a positive role by providing flycatcher 

breeding habitat. However, because rivers and reservoirs are 

not managed solely to create and maintain flycatcher habitat, 

the persistence of riparian vegetation in these systems—and 

any flycatchers breeding therein—is not assured.

Although the historic degradation and loss of native 

riparian negatively affected the Southwestern Willow 

Flycatcher, this species does not show an inherent preference 

for native vegetation. Instead, breeding habitat selection 

is based primarily on vegetation structure, density, size, 

and other stand characteristics, and presence of water or 

saturated soils (U.S. Fish and Wildlife Service, 2002). In fact, 

approximately 25 percent of known territories are found in 

habitat composed of 50 percent or greater exotic vegetative 

component—primarily saltcedar (Durst and others, 2008a). 

Saltcedar also can be an important habitat component in 

sites dominated by native vegetation (U.S. Fish and Wildlife 

Service, 2002, 2005). Despite suggestions that flycatchers 

breeding in saltcedar are suffering negative consequences 

and that removal of saltcedar is therefore a benefit (DeLoach 

and others, 2000; Dudley and DeLoach, 2004), there is 

increasing and substantial evidence that this is not the case. 

For example, Paxton and others (2007) found that flycatchers 

did not suffer any detectable negative consequences from 

breeding in saltcedar. This is consistent with the findings 

of Owen and others (2005) and Sogge and others (2006). 

Therefore, the rapid or large-scale loss of saltcedar in occupied 

flycatcher habitats, without rapid replacement of suitable 

native vegetation, could result in reduction or degradation 

of flycatcher habitat (U.S. Fish and Wildlife Service, 2002; 

Sogge and others, 2008).

In evaluating Southwestern Willow Flycatcher use of 

either native or exotic habitat, it is important to recognize that 

throughout the Southwest, there are many saltcedar-dominated 

and native-dominated habitats in which flycatchers do not 

breed (U.S. Fish and Wildlife Service, 2002; Sogge and 

others, 2006). Therefore, the use of any riparian patch—native 

or exotic—as breeding habitat will be site specific and will 

depend on the spatial, structural, and ecological characteristics 

of that particular patch and the potential for flycatchers to 

colonize and maintain populations within it.

Drought can have substantial negative effects on 

breeding flycatchers and their breeding habitat by reducing 

riparian vegetation vigor and density, and reducing prey 

availability (Durst, 2004; Paxton and others, 2007; Bureau 

of Reclamation, 2009). For example, the extreme drought of 

2002 caused near complete reproductive failure of the large 

flycatcher population at Roosevelt Lake; among approximately 

150 breeding territories, only two nests successfully fledged 

young in that year (Ellis and others, 2008). If future climate 

change produces more frequent or more sustained droughts, 

as predicted by many climate change models (for example, 

Seager and others, 2007), southwestern riparian habitats could 

be reduced in extent or quality. This scenario would present 

a challenge to the long-term sustainability of Southwestern 

Willow Flycatcher populations. 

Brood parasitism by the Brown-headed Cowbird 

(Molothrus ater) was initially considered another significant 

threat to the Southwestern Willow Flycatcher (Whitfield, 

1990; Harris, 1991; U.S. Fish and Wildlife Service, 1993, 

1995; Whitfield and Strong, 1995; Sferra and others, 

1997). Cowbirds lay their eggs in the nest of other species 

(the “hosts”), which raise the young cowbirds—often at 

the expense of reduced survivorship of their own young. 

Southwestern Willow Flycatchers seldom fledge any flycatcher 

young from nests that are parasitized by cowbirds (Whitfield 

and Sogge, 1999). Although parasitism negatively impacts 

some Southwestern Willow Flycatcher populations, especially 

at small and isolated breeding sites, it is highly variable and 

no longer considered among the primary rangewide threats 

to flycatcher conservation (U.S. Fish and Wildlife Service, 

2002). Cowbird abundance, and therefore parasitism, tends to 

be a function of habitat type and quality, and the availability of 

suitable hosts, not specific to the flycatcher. Therefore, largescale cowbirds control may not always be warranted unless 

certain impact thresholds are met (U.S. Fish and Wildlife 

Service, 2002; Rothstein and others, 2003; Siegle and Ahlers, 

2004).
16 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

Section 2. Survey Protocol

The fundamental principles of the methodology described 

in this version have remained the same since the original 

Tibbitts and others (1994) and subsequent Sogge and others 

(1997a) protocols: the use of vocalization play-back, repeated 

site visits, and confirmation of flycatcher identity via the 

species-characteristic song. This newest protocol incorporates 

guidelines of the 2000 USFWS addendum, and includes 

changes based on our improved understanding of Willow 

Flycatcher biology and the significance of potential threats, 

and the availability of new survey technologies. 

Several factors work together to make Southwestern 

Willow Flycatcher surveys challenging. Difficulties include 

the flycatcher’s physical similarities with other species and 

subspecies; accessing the dense habitat they occupy; time 

constraints based on their breeding period; and vocalization 

patterns. Given these challenges, no methodology can assure 

100-percent detection rates. However, the survey protocol 

described herein has proven to be an effective tool for locating 

flycatchers, and flycatchers generally are detectable when the 

protocol is carefully followed. Since 1995, hundreds of sites 

have been surveyed and thousands of flycatchers detected 

using the two previous versions of the survey protocol. 

The Willow Flycatcher is 1 of 10 regularly occurring 

Empidonax flycatchers found in North America, all of which 

look very much alike. Like all Empidonax, Willow Flycatchers 

are nondescript in appearance, making them difficult to see in 

dense breeding habitat. Although the Willow Flycatcher has 

a characteristic fitz-bew song that distinguishes it from other 

birds (including other Empidonax), Willow Flycatchers are not 

equally vocal at all times of the day or during all parts of the 

breeding season. Because Southwestern Willow Flycatchers 

are rare and require relatively dense riparian habitat, they may 

occur only in a small area within a larger riparian system, thus 

decreasing detectability during general bird surveys. Migrating 

Willow Flycatchers (of all subspecies) often sing during 

their migration through the Southwest, and could therefore 

be confused with local breeders. In addition, Southwestern 

Willow Flycatchers are in breeding areas for only 3–4 months 

of the year. Surveys conducted too early or late in the year 

would fail to find flycatchers even at sites where they breed.

These life history characteristics and demographic factors 

influence how Southwestern Willow Flycatcher surveys 

should be conducted and form the basis upon which this 

protocol was developed. This protocol is based on the use of 

repeated call-playback surveys during pre-determined periods 

of the breeding season, to confirm presence or to derive a high 

degree of confidence regarding their absence at a site. Such 

species-specific survey techniques are necessary to collect 

reliable presence/absence information for rare species (Bibby 

and others, 1992).

The primary objective of this protocol is to provide 

a standardized survey technique to detect Southwestern 

Willow Flycatchers, determine breeding status, and facilitate 

consistent and standardized data reporting. The survey 

technique will, at a minimum, help determine presence or 

absence of the species in the surveyed habitat for that breeding 

season. Ultimately, the quality of the survey that is conducted 

will depend on the preparation, training, and in-the-field 

diligence of the individual surveyor.

This protocol is designed for use by persons who are 

non-specialists with Empidonax flycatchers or who are not 

expert birders. However, surveyors must have sufficient 

knowledge, training, and experience with bird identification 

and surveys to distinguish the Willow Flycatcher from other 

non-Empidonax species, and be able to recognize the Willow 

Flycatcher’s primary song. A surveyor’s dedication and 

attitude, willingness to work early hours in dense, rugged 

and wet habitats, and their ability to remain alert and aware 

of important cues also are important. Surveys conducted 

improperly or by unqualified, inexperienced, or complacent 

personnel may lead to inaccurate results and unwarranted 

conclusions.

Surveys conducted by qualified personnel in a consistent 

and standardized manner will enable continued monitoring 

of general population trends at and between sites, and 

between years. Annual or periodic surveys in cooperation 

with State and Federal agencies should aid resource managers 

in gathering basic information on flycatcher status and 

distribution at various spatial scales. Identifying occupied and 

unoccupied sites will assist resource managers in assessing 

potential impacts of proposed projects, avoiding impacts to 

occupied habitat, identifying suitable habitat characteristics, 

developing effective restoration management plans, and 

assessing species recovery.

The earlier versions of this protocol (Tibbitts and others, 

1994; Sogge and others, 1997a) were used extensively and 

successfully for many years. Hundreds of flycatcher surveys 

conducted throughout the Southwest since 1994 revealed 

much about the usefulness and application of this survey 

technique. Three important lessons were: (1) the call-playback 

technique works and detects flycatchers that would have 

otherwise been overlooked; (2) multiple surveys at each 

site are important; and (3) with appropriate effort, general 

biologists without extensive experience with Empidonax can 

find and verify Willow Flycatcher breeding sites. 

This revised protocol is still based on call-playback 

techniques and detection of singing individuals. However, 

it includes changes in the timing and number of surveys to 

increase the probability of detecting flycatchers and to help 

determine if they are breeders or migrants. It also incorporates 

the basic premise of the USFWS 2000 addendum to the 

1997 protocol by requiring a minimum of five surveys in all 

“project-related” sites. A detailed description of surveys and 
Section 2. Survey Protocol 17

timing is discussed in section, “Timing and Number of Visits.” 

Changes in the survey data sheets make them easier to use and 

submit, and allow reporting all site visits within a single year 

on one form. The new survey forms also are formatted such 

that the data on the respective forms can be easily incorporated 

into the flycatcher range-wide database.

This protocol is intended to determine if a habitat patch 

contains territorial Southwestern Willow Flycatchers, and is 

not designed establish the exact distribution and abundance of 

flycatchers at a site. Determining precise flycatcher numbers 

and locations requires many more visits and additional 

time observing the behavior of individual birds. This 

survey protocol also does not address issues and techniques 

associated with nest monitoring or other flycatcher research 

activities. Those efforts are beyond the scope usually needed 

for most survey purposes, and require advanced levels of 

experience and skills to gather useful data and avoid potential 

negative effects to the flycatcher. If nest monitoring is a 

required component of your study, refer to Rourke and others 

(1999) for appropriate nest monitoring techniques (available 

for download at http://sbsc.wr.usgs.gov/cprs/research/projects/

swwf/reports.asp).

Biologists who are not expert birders or specialists 

with regard to Empidonax flycatchers can effectively use 

this protocol. However, users should attend a U.S. Fish and 

Wildlife Service-approved Southwestern Willow Flycatcher 

survey training workshop, and have knowledge and experience 

with bird identification, surveys, and ecology sufficient to 

effectively apply this protocol.

Permits

Federal endangered species recovery permits are 

required for surveys in all USFWS regions where the 

Southwestern Willow Flycatcher breeds (application forms 

can be downloaded at http://www.fws.gov/forms/3-200-55.

pdf). State permits also may be required before you can survey 

within any of the States throughout the Southwestern Willow 

Flycatcher’s range: be certain to check with the appropriate 

State wildlife agency in your area. It usually takes several 

months to receive permits, so apply early to avoid delays 

in starting your surveys. You also must obtain permission 

from government agencies and private landowners prior to 

conducting any surveys on their lands.

Pre-Survey Preparation

The degree of effort invested in pre-survey preparation 

will have a direct effect on the quality and efficiency of 

the surveys conducted. Pre-survey preparation is often 

overlooked, but can prove to be one of the more important 

aspects in achieving high-quality survey results.

Surveyors should study calls, songs, drawings, 

photographs, and videos of Willow Flycatchers. Several 

web sites describe life history requirements, and provide 

photographs and vocalizations. It is especially critical for 

surveyors to be familiar with Willow Flycatcher vocalizations 

before going in the field. Although the fitz-bew song is the 

basis of verifying detections using this protocol, Willow 

Flycatchers use many other vocalizations that are valuable in 

locating birds and breeding sites. We strongly encourage that 

all surveyors learn as many vocalizations as possible and refer 

to the on-line “Willow Flycatcher Vocalizations; a Guide for 

Surveyors” (available at http://sbsc.wr.usgs.gov/cprs/research/

projects/swwf/wiflvocl.asp). Several commercial bird song 

recordings include Willow Flycatcher vocalizations, but these 

recordings typically have only a few vocalizations and the 

dialects may differ from those heard in the Southwest.

If possible, visit known Willow Flycatcher breeding 

sites to become familiar with flycatcher appearance, behavior, 

vocalizations, and habitat. Such visits are usually part of the 

standardized flycatcher survey workshops. All visits should 

be coordinated with USFWS, State wildlife agencies, and 

the property manager/owner, and must avoid disturbance to 

territorial flycatchers. While visiting these sites, carefully 

observe the habitat characteristics to develop a mental image 

of the key features of suitable habitat. 

Surveyors must be able to identify, by sight and 

vocalizations, other species likely to be found in survey areas 

that may be confused with Southwestern Willow Flycatchers. 

These include Bell’s Vireo (Vireo bellii), Western Woodpewee (Contopus sordidulus), young or female Vermillion 

Flycatchers (Pyrocephalus rubinus), and other Empidonax

flycatchers. At a distance, partial song or call notes of Bell’s 

Vireo, Ash-throated Flycatchers (Myiarchus cinerascens) 

and some swallows can sound considerably like a fitz-bew. 

Surveyors also should be able to identify Brown-headed 

Cowbirds by sight and vocalizations. It is worthwhile to 

make one or more pre-survey trips to the survey sites or other 

similar areas to become familiar with the local bird fauna. You 

might consider obtaining a species list relative to your area 

and become familiar with those species by site and sound.

Prior to conducting any presence/absence surveys in your 

respective State or USFWS Region, contact the respective 

flycatcher coordinators to discuss the proposed survey 

sites and determine if the sites have been surveyed in prior 

years. If possible, obtain copies of previous survey forms 

and maintain consistency with naming conventions and site 

boundaries. Study the forms to determine if flycatchers have 

been previously detected in the site, record locations of any 

previous detections, and read the comments provided by prior 

surveyors. While surveying, be sure to pay special attention to 

any patches where flycatchers have previously been detected.
18 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

Familiarity with the survey site prior to the first surveys 

is the best way to be prepared for the conditions you will 

experience. Determine the best access routes to your sites 

and always have a back-up plan available in the event of 

unforeseen conditions (for example, locked gates, weather, 

etc.). Know the local property boundaries and where the 

potential hazards may be, including deep water, barbed wire 

fencing, and difficult terrain. Be prepared to work hard and 

remain focused and diligent in a wide range of physically 

demanding conditions. At many sites, these include heat, cold, 

wading through flowing or stagnant water, muddy or swampy 

conditions, crawling through dense thickets (often on hands 

and knees), and exposure to snakes, skunks, and biting insects. 

It is imperative that all surveyors exercise the adage 

“safety first.” Be aware of safety hazards and how to avoid 

them, and do not allow the need to conduct surveys to 

supersede common sense and safety. Inform your coworkers 

where you will be surveying and when you anticipate 

returning. Always take plenty of water and know how to 

effectively use your equipment, especially compass, Global 

Positioning System (GPS), and maps.

Equipment 

The following equipment is necessary to conduct the 

surveys:

1. USGS topographic maps of the area: A marked copy 

is required to be attached to survey data sheets submitted 

at the end of the season. Be sure to always delineate the 

survey area and clearly mark any flycatcher detections. 

If the survey area differed between visits; delineate each 

survey individually.

2. Standardized survey form: Always bring more copies 

than you think you need.

3. Lightweight audio player: Be sure the player has 

adequate volume to carry well; use portable speakers if 

necessary. Several digital devices, such as CD players 

and MP3 players, are currently available and can be 

connected to external amplified speakers for broadcasting 

the flycatcher vocalizations. However, not all are equally 

functional or effective in field conditions; durability, 

reliability, and ease of use are particularly important. 

Talk to experienced surveyors for recommendations on 

particular models and useful features.

4. Extra player and batteries: In the field, dirt, water, 

dust, and heat often cause equipment failure, and having 

backup equipment helps avoid aborting a survey due to 

equipment loss or failure.

5. Clipboard and permanent (waterproof) ink pen: We 

recommend recording survey results directly on the 

survey data form, to assure that you collect and record all 

required data and any field notes of interest.

6. Aerial photographs: Aerial photographs can significantly 

improve your surveys by allowing you to accurately 

target your efforts, thus saving time and energy in the 

field. Previously, aerial images were often expensive and 

difficult to obtain. However, it is now easy to get free or 

low-cost images from sources, such as Google© Earth. 

Even moderate resolution images generally are better 

than none. For higher resolution aerial photographs, 

check with local planning offices and/or State/Federal 

land-management agencies for availability. Take color 

photocopies, not the original aerial photographs, with you 

in the field. Aerial photographs also are very useful when 

submitting your survey results but cannot be substituted in 

lieu of the required topographic map.

7. Binoculars and bird field guide: Although this protocol 

relies primarily on song detections to verify flycatcher 

presence, good quality binoculars are still a crucial field 

tool to help distinguish between possible Southwestern 

Willow Flycatchers and other species. Use a pair with 

7–10 power magnification that can provide crisp images 

in poor lighting conditions. A good field guide also is 

essential for the same reason.

8. GPS unit: A GPS unit is needed for determining survey 

coordinates and verifying the location of survey plots 

on topographic maps. All flycatcher detections should 

be stored as waypoints and coordinates recorded on 

the survey form. A wide variety of fairly inexpensive 

GPS units are currently available. Most commercially 

available units will provide accuracy within 10 m, which 

is sufficient for navigating and marking locations.

9. Compass: Surveyors should carry a compass to help 

them while navigating larger habitat patches. This is 

an important safety back-up device, because GPS units 

can fail or lose power. Most GPS units have a feature 

to provide an accurate bearing to stored waypoints (for 

example, previous flycatcher detections, your parked 

vehicle, etc.); however, many units do not accurately 

display the direction in which the surveyor is traveling 

slowly through dense vegetation. A compass set to 

the proper bearing provides a more reliable method to 

navigate the survey site and relocate previously marked 

locations.

The following equipment also is recommended:

10. Camera: These are very helpful for habitat photographs, 

especially at sites where flycatchers are found. Small 

digital cameras are easily portable and relatively 

inexpensive.

11. Survey flagging: Used for marking survey sites or areas 

where flycatcher are detected. Check with the local land 

owner or management agency before flagging sites. Use 

flagging conservatively so as to not attract people or 

predators.

12. Field vest: A multi-pocket field vest can be very useful 

for carrying field equipment and personal items. We 

recommend muted earth-tone colors.
Section 2. Survey Protocol 19

13. Cell phone and/or portable radio: In addition to 

providing an increased level of safety, cell phones or 

portable radios may be used by surveyors to assist each 

other in identifying territories and pairs in dense habitats, 

or where birds are difficult to hear.

In addition to the necessary equipment mentioned above, 

personal items, such as food, extra water or electrolyte drink, 

sunscreen, insect repellent, mosquito net, first-aid kit, whistle, 

and a light jacket, also should be considered. Being prepared 

for unforeseen difficulties, and remaining as comfortable as 

conditions allow while surveying are important factors to 

conducting thorough and effective surveys. 

All survey results (both negative and positive) should 

be recorded directly on data forms when possible. These 

data forms have been designed to prompt surveyors to 

record key information that is crucial to interpretation of 

survey results and characterization of study sites. Even if no 

flycatchers are detected or habitat appears unsuitable, this is 

valuable information and should be recorded. Knowing where 

flycatchers are not breeding can be as important as knowing 

where they are; therefore, negative data are important. 

Standardized data forms are provided in appendix 1, or can be 

downloaded online. Always check for updated forms prior to 

each year’s surveys.

Willow Flycatcher surveys are targeted at this species 

and require a great deal of focused effort. Surveyors must 

be constantly alert and concentrate on detecting a variety of 

flycatcher cues and responses. Therefore, field work, such as 

generalized bird surveys (for example, point counts or walking 

transects) or other distracting tasks, should not be conducted in 

conjunction with Willow Flycatcher surveys. Avoid bringing 

pets or additional people who are not needed for the survey. 

Dress in muted earth-tone colors, and avoid wearing bright 

clothing.

Willow Flycatcher Identification

The Southwestern Willow Flycatcher is a small bird, 

approximately 15 cm long and weighing about 11–12 g. Sexes 

look alike and cannot be distinguished by plumage. The upper 

parts are brownish-olive; a white throat contrasts with the pale 

olive breast, and the belly is pale yellow. Two white wing bars 

are visible (juveniles have buffy wing bars) and the eye ring 

is faint or absent. The upper mandible is dark and the lower 

mandible light. The tail is not strongly forked. When perched, 

the Willow Flycatcher often flicks its tail upward. As a group, 

the Empidonax flycatchers are very difficult to distinguish 

from one another by appearance. The Willow Flycatcher also 

looks very similar to several other passerine species you may 

encounter in the field.

Given that Willow Flycatchers look similar to other 

Empidonax flycatchers that may be present at survey sites, 

the most certain way to verify Willow Flycatchers in the field 

is by their vocalization. For the purpose of this protocol, 

identification of Willow Flycatchers cannot be made by sight 

alone; vocalizations are a critical identification criterion, and 

specifically the primary song fitz-bew. Willow Flycatchers 

have a variety of vocalizations (see Stein, 1963; Sedgwick, 

2000), but two are most commonly heard during surveys or in 

response to call-playback:

1. Fitz-bew. This is the Willow Flycatcher’s characteristic 

primary song. Note that fitz-bews are not unique to the 

southwestern subspecies; all Willow Flycatchers sing this 

characteristics song. Male Willow Flycatchers may sing 

almost continuously for hours, with song rates as high 

as one song every few seconds. Song volume, pitch, and 

frequency may change as the season progresses. During 

prolonged singing bouts, fitz-bews are often separated 

by short britt notes. Fitz-bews are most often given by a 

male, but studies have shown female Willow Flycatchers 

also sing, sometimes quite loudly and persistently 

(although generally less than males). Flycatchers often 

sing from the top of vegetation, but also will vocalize 

while perched or moving about in dense vegetation.

2. Whitt. This is a call often used by nesting pairs on their 

territory, and commonly is heard even during periods 

when the flycatchers are not singing (fitz-bewing). The 

whitt call appears to be a contact call between sexes, as 

well as an alarm call, particularly when responding to 

disturbance near the nest. Whitt calls can be extremely 

useful for locating Willow Flycatchers later in the season 

when fitz-bewing may be infrequent, but are easily 

overlooked by inexperienced surveyors. When flycatcher 

pairs have active nests and particularly once young have 

hatched, whitts may be the most noticeable vocalization. 

However, many species of birds whitt, and a whitt is 

not a diagnostic characteristic for Willow Flycatchers. 

For example, the “whitt” of the Black-headed Grosbeak 

(Pheucticus melanocephalus) and Yellow-breasted 

Chat (Icteria virens) are often confused with that of the 

flycatcher. 

The fitz-bew and whitt calls are the primary vocalizations 

used to locate Willow Flycatchers. However, other less 

common Willow Flycatcher vocalizations can be very useful 

in alerting surveyors to the presence of flycatchers. These 

include twittering vocalizations typically given during 

interactions between flycatchers and sometimes between 

flycatchers and other birds, bill snapping, britt’s, and wheeo’s. 

Because these sounds can be valuable in locating territories 

(Shook and others, 2003), they should be studied prior to 

going in the field. Willow Flycatcher vocalization recordings 

are available from Federal and State agency contacts and 

online at http://sbsc.wr.usgs.gov/cprs/research/projects/swwf/. 

Standardized recordings of Southwestern Willow Flycatchers 

also are available online at http://www.naturesongs.com/

tyrrcert.html#tyrr. Specifically, only fitz-bews and britts

should be used for conducting surveys, to provide more robust 

comparative results among sites and years.
20 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

Willow Flycatcher song rates are highest early in the 

breeding season (late May–early June), and typically decline 

after eggs hatch. However, in areas with many territorial 

flycatchers or where an unpaired flycatcher is still trying 

to attract a mate, or where re-nesting occurs, singing rates 

may remain high well into July. Isolated pairs can be much 

quieter and harder to detect than pairs with adjacent territorial 

flycatchers. At some sites, pre-dawn singing (0330–

0500 hours) appears to continue strongly at least through 

mid-July (Sogge and others, 1995). Singing rates may increase 

again later in the season, possibly coinciding with re-nesting 

attempts (Yard and Brown, 2003). The social dynamics of 

adjacent territories can strongly influence vocalization rates. 

A single “fitz-bew” from one flycatcher may elicit multiple 

responses from adjacent territories. When these interactions 

occur, it is a good opportunity to distinguish among territories 

and provides the surveyor with an estimate of territory 

numbers in the immediate area.

There are some periods during which Willow Flycatchers 

do not sing and even the use of call-playback sometimes fails 

to elicit any response. This can be particularly true late in the 

breeding season. Early and repeated surveys are the best way 

to maximize the odds of detecting a singing flycatcher and 

determining its breeding status.

Timing and Number of Visits

No survey protocol can guarantee that a Southwestern 

Willow Flycatcher, if present, will be detected on any single 

visit. However, performing repeated surveys during the early 

to mid-nesting season increases the likelihood of detecting 

flycatchers and aids in determining their breeding status. A 

single survey, or surveys conducted too early or late in the 

breeding cycle, do not provide definitive data and are of 

limited value. 

For purposes of this survey protocol, we have divided 

the Southwestern Willow Flycatcher breeding season into 

three basic survey periods, and specified a minimum number 

of survey visits for each period (fig. 9). Although the Sogge 

and others (1997a) protocol recommended a minimum of one 

survey in each period, we now recommend a differing number 

of visits for general surveys versus project-related studies. 

General surveys are conducted for the sole purpose of 

determining whether Willow Flycatchers are present or absent 

from a respective site, when there is no foreseeable direct or 

indirect impact to their habitat from a known potential project 

or change in site management. In such cases, a minimum of 

one survey visit is required in each of the three survey periods.

Project-related surveys are conducted to determine the 

presence or absence of Willow Flycatchers within a site when 

there is a potential or foreseeable impact to their habitat due to 

a potential project or change in site management. Additional 

surveys are required for project-related studies in order to 

derive a greater degree of confidence regarding the presence or 

absence of Willow Flycatchers. 

All successive surveys must be at least 5 days apart; 

surveys conducted more closely are not considered to be 

separate surveys. Although a minimum of three or five 

surveys are required for general and project-related purposes, 

respectively, if the habitat patches are large, contiguous and 

extremely dense, additional surveys are strongly encouraged 

to ensure full coverage of the site.

If you are uncertain whether three general surveys or 

five project-related surveys are required for your respective 

study, contact your USFWS flycatcher coordinator. As noted 

earlier, this survey protocol will help determine if territorial 

flycatchers are present and their approximate locations; if your 

project requires fine-scale estimates of flycatcher numbers or 

distribution at a site, you may need to conduct more intensive 

efforts that include additional surveys, nest searches, and nest 

monitoring.

Survey Period 1: May 15–31.—For both general and 

project-related surveys: a minimum of one survey is required. 

The timing of this survey is intended to coincide with the 

period of high singing rates in newly arrived males, which 

tends to begin in early to mid-May. This is one of the most 

reliable times to detect flycatchers that have established their 

territories, so there is substantial value to conducting period 1 

surveys even though not all territorial males may yet have 

arrived. Migrant Willow Flycatchers of multiple subspecies 

will likely be present and singing during this period. Because 

both migrant and resident Willow Flycatchers are present 

during this period, and relatively more abundant then in 

subsequent surveys, it is an excellent opportunity to hone 

your survey and detection skills and gain confidence in your 

abilities. Detections of flycatchers during period 1 also provide 

insight on areas to pay particular attention to during the next 

survey period.

 Survey Period 2: June 1–24.—For general surveys: 

a minimum of one survey is required. For project-related 

surveys, a minimum of two surveys are required. Note 

that this differs from the minimum of one survey that was 

recommended in this period under the previous protocol 

(Sogge and others, 1997a). During this period, the earliest 

arriving males may already be paired and singing less, but 

later arriving males should still be singing strongly. Period 2 

surveys can provide insight about the status of any flycatchers 

detected during survey period 1. For example, if a flycatcher 

is detected during survey period 1 but not survey period 2, the 

first detection may have been a migrant. Conversely, detecting 

a flycatcher at the same site during periods 1 and 2 increases 

the likelihood that the bird is not a migrant, although it does 

not necessarily confirm it. Survey period 2 also is the earliest 

time during which you are likely to find nesting activity by 

resident birds at most sites. Special care should be taken 

during this period to watch for activity that will verify whether 

the flycatchers that are present are attempting to breed. A little 

extra time and diligence should be spent at all locations where 

flycatchers were detected during survey period 1. 
Section 2. Survey Protocol 21

General surveys 

Project surveys 

Survey Period 1 Survey Period 2 Survey Period 3 

Survey Visit Timing, Numbers, and Detection Interpretation 

Minimum 1 survey this period

Minimum 1 survey this period

Minimum 1 survey this period

Minimum 2 surveys this period

Minimum 1 survey this period

Minimum 2 surveys this period

Flycatchers very vocal and

responsive this period. Birds

detected during this period could be

migrants or territorial. If detected

only in Period 1, birds are likely

migrants. Evidence of breeding can

confirm territorial status.

Territorial birds generally nesting and

less vocal. Birds detected during this

period could be migrants or territorial. 

If detected only in Period 2, birds are 

probably migrants unless other 

evidence of breeding noted.

Flycatchers are generally much less

vocal during this period. All birds

detected in Period 3 are considered

territorial. Observation of breeding

activities can help determine if

territorial birds are paired and

nesting.

May 15 June 1 June 24 July 17

Figure 9. Recommended numbers and timing of visits during each survey period for general surveys and project surveys. General 

surveys are those conducted when there is no foreseeable direct or indirect impact to their habitat from a known potential project or 

change in site management. Project-related surveys are conducted when there is a potential or foreseeable impact to their habitat due 

to a potential project or change in site management.

Survey Period 3: June 25–July 17.—For general surveys, 

a minimum of one survey is required. For project-related 

surveys, a minimum of two surveys are required. Virtually 

all Southwestern Willow Flycatchers should have arrived on 

their territories by this time. Flycatcher singing rates probably 

have lessened, and most paired flycatchers will have initiated 

or even completed their first round of nesting activity. Migrant 

Willow Flycatchers should no longer be passing through the 

Southwest; therefore, any flycatchers that you detect are likely 

to be either territorial or nonbreeding floaters. Surveyors 

should determine if flycatchers detected during surveys in 

periods 1 or 2 are still present, and watch closely for nesting 

activity. Flycatchers that have completed a first nesting attempt 

may resume vigorous singing during this period. Extra time 

and diligence should be spent at all locations where flycatchers 

were detected during survey periods 1 or 2. 

At high elevation sites (above 2,000 m), Southwestern 

Willow Flycatcher arrival and initiation of breeding activities 

may occur in early June, and possibly later in some years 

due to weather or migration patterns. Therefore, flycatcher 

breeding chronology may be delayed by 1 or 2 weeks at such 

sites, and surveys should be conducted in the latter part of 

each period. 

It may not require multiple surveys to verify 

Southwestern Willow Flycatcher presence or breeding status. 

If, for example, Willow Flycatchers are observed carrying 

nest material during survey periods 1 or 2, this is conclusive 

verification they are breeders as opposed to migrants, 

regardless of what is found during period 3. However, it 

requires a minimum of three surveys for general studies and 

five surveys for project-related studies to determine with 

relative confidence that Southwestern Willow Flycatchers 

probably are not breeding at a site in that year, based on lack 

of detections. 

We strongly encourage additional follow-up surveys to 

sites where territorial Southwestern Willow Flycatchers are 

verified or suspected. Extra surveys provide greater confidence 

about presence or absence of flycatchers at a site, as well as 

help in estimating the number of breeding territories or pairs, 

and determining breeding status and the outcome of breeding 

efforts. Pre-survey visits the evening before the survey or 

post-survey follow-up later in the morning can help confirm 

breeding status when surveyors are not under time constraints. 

However, avoid returning to a site so often as to damage the 

habitat, establish or enlarge trails, or cause undue disturbance 

to the flycatchers.
22 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

Survey Methods

The survey methods described below fulfill the primary 

objectives of documenting the presence or absence of Willow 

Flycatchers, and determining their status as territorial versus 

migrant. This protocol primarily is a call-playback technique, 

a proven method for eliciting response from nearby Willow 

Flycatchers (Seutin, 1987; Craig and others, 1992), both 

territorial and migrants. The premise of the call-playback 

technique is to simulate a territorial intrusion by another 

Willow Flycatcher, which generally will elicit a defensive 

response by the territorial bird, increasing its detectability. 

At each site, surveyors should broadcast a series of recorded 

Willow Flycatcher fitz-bews and britts, and look and listen 

for responses. In addition to maximizing the likelihood of 

detecting nearby flycatchers, this method also allows for 

positive identification by comparing the responding bird’s 

vocalizations to the known Willow Flycatcher recording.

Documenting Presence /Absence—Begin surveys 

as soon as there is enough light to safely walk (about 

1 hour before sunrise) and end by about 0900–1030 hours, 

depending on the temperature, wind, rain, background noise, 

and other environmental factors. Use your best professional 

judgment whether to conduct surveys that day based on 

local field conditions. If the detectability of flycatchers is 

being reduced by environmental factors, surveys planned for 

that day should be postponed until conditions improve. If 

observers are camped in or near potential Willow Flycatcher 

habitat, afternoons and evenings can be spent doing site 

reconnaissance and planning a survey strategy for the 

following morning. If camped immediately adjacent to survey 

sites, surveyors can awaken early and listen for flycatchers 

singing during the predawn period (0330–0500 hours), when 

territorial males often sing loudly.

Conduct surveys from within rather than from the 

perimeter of the sites, while limiting the breaking of 

vegetation or damaging the habitat. If surveys cannot be 

conducted from within the habitat, walk along the perimeter 

and enter the patch at intervals to broadcast the vocalizations 

and listen for responses. Flycatchers often respond most 

strongly if the recording is played from within the habitat and 

territory, rather than from the periphery. In addition, it can be 

surprisingly difficult to hear singing Willow Flycatchers that 

are even a short distance away amidst the noise generated 

by other singing and calling birds, roads, noisy streams, and 

other extraneous sounds. Therefore, it is preferable to survey 

from within the habitat, but always move carefully to avoid 

disturbing habitat or nests. Surveying from the periphery 

should not be conducted only for the sake of convenience, 

but is allowable for narrow linear reaches or when absolutely 

necessary due to safety considerations.

Because flycatchers may be clustered within only a 

portion of a habitat patch, it is critical to survey all suitable 

habitat within the patch. Small linear sites may be thoroughly 

covered by a single transect through the patch. For larger sites, 

choose a systematic survey path that assures complete patch 

coverage throughout the length and breadth of the site. This 

may require multiple straight transects, serpentine, zig-zag, 

or criss-cross routes. Aerial photographs and previous survey 

forms are valuable tools to help plan and conduct surveys, and 

to assure complete coverage. Always move carefully through 

the habitat to avoid disturbing vegetation or nests. 

Initially approach each site and stand quietly for 

1–2 minutes or longer, listening for spontaneously singing 

flycatchers. A period of quiet listening is important because 

it helps acclimate surveyors to background noises that can 

be quite loud due to roads, aircraft, machinery, waterways, 

and other sounds. It also allows surveyors to recognize 

and shift attention away from the songs and calls of other 

bird species, letting them focus on listening for flycatchers. 

Although it happens rarely, some singing Willow Flycatchers 

will actually stop vocalizing and approach quietly in response 

to a broadcast song, perhaps in an effort to locate what they 

perceive as an intruding male. Therefore, playing a recording 

before listening for singing individuals has at least some 

potential of reducing detectability.

If you do not hear singing flycatchers during the initial 

listening period, broadcast the Willow Flycatcher song 

recording for 10–15 seconds; then listen for approximately 

1 minute for a response. Repeat this procedure (including a 

10-second quiet pre-broadcast listening period) every 20–30 m 

throughout each survey site, more often if background noise is 

loud. The recording should be played at about the volume of 

natural bird calls, and not so loud as to cause distortion of the 

broadcast. We recommend that the playback recording include 

a series of fitz-bews interspersed with several britts.

Response to the broadcast call could take several forms. 

Early in the breeding season (approximately May–mid-June), 

a responding Willow Flycatcher will usually move toward 

the observer and fitz-bew or whitt from within or at the top 

of vegetation. Territorial Willow Flycatchers almost always 

vocalize strongly when a recording is played in their territory 

early in the season. If there are several flycatchers present 

in an area, some or all may start singing after hearing the 

recording or the first responding individual. Flycatchers can 

often hear the recording from far away but will not usually 

move outside of their territory, so listen for distant responses. 

Also, stay alert and listen for flycatchers vocalizing behind 

you that may not have responded when you were first in their 

territory. Another common flycatcher response is alarm calls 

(whitts) or interaction twitters from within nearby vegetation, 

particularly once nesting has begun. Willow Flycatchers will 

often sing after a period of whitting in response to a recording, 

so surveyors hearing whitts should remain in the area and 

quietly listen for fitz-bews for several minutes. Because some 

flycatchers may initially respond by approaching quietly, 

particularly during periods 2 and 3, it is critical to watch 

carefully for responding birds. 
Section 2. Survey Protocol 23

If you detect flycatchers that appear particularly agitated, 

it is possible that you are in close proximity to their nest. 

Agitated flycatchers may swoop down at the surveyor, snap 

their beaks, and otherwise appear distressed. Exercise extreme 

caution so as to not accidently disturb the nest, and move 

slowly away from the immediate area. 

For the purpose of this protocol, detection of a fitz-bew

song is essential to identify a bird as a Willow Flycatcher. 

Similar appearing species (including other Empidonax

flycatchers) occur as migrants, and even breeders, at potential 

Willow Flycatcher sites. A few of these other species may even 

approach a broadcast Willow Flycatcher song and respond 

with vocalizations. In order to standardize interpretation 

of survey results and assure a high degree of confidence in 

surveys conducted by biologists of varying experience and 

skill, positive identification must be based on detection of the 

Willow Flycatcher’s most unique characteristic—its song. It 

is important to remember that the whitt call is not unique to 

Willow Flycatchers, and therefore cannot serve as the basis 

of a positive identification. However, whitts are extremely 

useful for locating flycatchers and identifying areas needing 

follow-up visits. Loud, strong whitting may indicate a nearby 

nest, dictating that surveyors exercise extra caution moving 

through the area.

Whenever a verified or suspected Willow Flycatcher 

is detected, be careful not to overplay the song recording. 

Excessive playing could divert the bird from normal breeding 

activities or attract the attention of predators and brood 

parasites. Wildlife management agencies may consider 

overplaying the recording as “harassment” of the flycatcher, 

and this is not needed to verify species identification. 

Although flycatchers usually sing repeatedly once prompted, 

even a single fitz-bew is sufficient for verification. If you have 

played a recording several times and a bird has approached 

but has not fitz-bewed, do not continue playing the recording. 

If a potential Willow Flycatcher responds, approaches or 

whitts but does not sing, it is best to carefully back away 

and wait quietly. If it is a Willow Flycatcher, it probably will 

sing within a short time (5–10 minutes). Another option is to 

return to the same site early the following morning to listen 

for or attempt to elicit singing again. If you are still uncertain, 

record the location with your GPS, record comments on the 

survey form, and follow-up on the detection during subsequent 

surveys. If possible, request the assistance of an experienced 

surveyor to determine positive identification.

If more habitat remains to be surveyed, continue onward 

once a flycatcher is detected and verified. In doing so, move 

30–40 m past the current detection before again playing the 

recording, and try to avoid double-counting flycatchers that 

have already responded. Willow Flycatchers, particularly 

unpaired males, may follow the broadcast song for 50 m or 

more.

Looking For and Recording Color Bands.—Several 

research projects have involved the capture and banding of 

Willow Flycatchers at breeding sites across the Southwest. 

In such projects, flycatchers are banded with one or more 

small colored leg bands, including a federal numbered band. 

As a result, surveyors may find color-banded individuals 

at their survey sites, and identification and reporting of the 

band combination can provide important data on flycatcher 

movements, survivorship, and site fidelity.

To look for bands, move to get a good view of the 

flycatcher’s legs. This may be difficult in dense vegetation, 

but flycatchers commonly perch on more exposed branches 

at the edges of their territory or habitat patch. If bands are 

seen, carefully note the band colors. If there is more than 

one band on a leg, differentiate the top (farthest up the leg) 

from the bottom (closest to the foot), and those on the bird’s 

left leg versus the right leg. If you are unsure of the color, do 

not guess. Instead, record the color as unknown. Incorrect 

color-band data are worse than incomplete data, so only record 

colors of which you are certain. The fact that a banded bird 

was seen, even without being certain of its color combination, 

is very important information. Record the color-band 

information on the survey form, and report the sighting to the 

appropriate State or Federal contact as soon as you return from 

the survey that day.

Determining the Number of Territories and Pairs.—

Accurately determining the number of breeding territories and 

pairs can be more difficult than determining simple presence 

or absence. Flycatcher habitat is usually so dense that visual 

detections are difficult, and seeing more than one bird at a 

time is often impossible. Flycatchers sing from multiple song 

perches within their territories, and may be mistaken for more 

than one flycatcher. A flycatcher responding to or following a 

surveyor playing a recording may move considerable distances 

in a patch and thus be counted more than once. Territorial 

male flycatchers often sing strongly, but so do many migrants 

and some females, particularly in response to call-playback 

(Seutin, 1987; Unitt, 1987; Sogge and others, 1997b). 

Rangewide, many territorial male flycatchers are unmated, 

particularly those in small breeding groups. For these reasons, 

each singing flycatcher may not represent a territory or a 

mated pair. Following the established survey protocol and 

carefully observing flycatcher behavior can help determine 

if you have detected migrants, territorial birds, breeders, 

unmated birds, or pairs.

Given sufficient time, effort and observation, it is 

usually possible to approximate the number of territories 

and pairs. First, listen carefully for simultaneously singing 

flycatchers. Note the general location of each bird—especially 

concurrently singing individuals—on aerial photographs, map, 

or a site sketch. Spend some time watching each flycatcher 

to determine approximate boundaries of its territory, and 

how it interacts with other flycatchers. If one or more singing 
24 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

birds stay primarily in mutually exclusive areas, they can be 

considered as separate territories. To determine if a flycatcher 

is paired, watch for interactions within a territory. Refer to the 

section, “Determining Breeding Status” for signs of pairing 

and breeding activity. Do not report a territorial male as a pair 

unless you observe one or more of the signs listed below. In 

some cases, it may be possible only to estimate the number of 

singing individuals. In other cases, it may take multiple site 

visits to differentiate territories or pairs. 

Determining Breeding Status.—One way to determine 

if the flycatchers found at a particular site are migrants or 

territorial is to find out if they are still present during the 

“non-migrant” period, which generally is from about June 15 

to July 20 (Unitt, 1987). A Willow Flycatcher found during 

this time probably is a territorial bird, although there is a 

small chance it could be a non-territorial floater (Paxton and 

others, 2007). If the management question is simply whether 

the site is a potential breeding area, documenting the presence 

of a territorial flycatcher during the non-migrant period may 

meet all survey objectives, and the site may not need to be 

resurveyed during the remainder of that breeding season.

However, in some cases, surveyors will be interested 

in knowing not only if territorial Southwestern Willow 

Flycatchers are present at a site, but also whether breeding 

or nesting efforts are taking place. Some males maintain 

territories well into July yet never succeed in attracting a mate, 

so unpaired males are not uncommon (McLeod and others, 

2007; Ellis and others, 2008; Ahlers and Moore, 2009). Thus, 

an assumption that each singing male represents a breeding 

pair may not be well founded, especially in small populations. 

If it is important to determine whether a pair is present and 

breeding in that territory, move a short distance away from 

where the bird was sighted, find a good vantage point, and 

sit or lie quietly to watch for evidence of breeding. Signs of 

breeding activity include:

a. observation of another unchallenged Willow Flycatcher in 

the immediate vicinity (indicates possible pair);

b. whitt calls between nearby flycatchers (indicates possible 

pair);

c. interaction twitter calls between nearby flycatchers 

(indicates possible pair);

d. countersinging or physical aggression against another 

flycatcher or bird species (suggests territorial defense);

e. physical aggression against cowbirds (suggests nest 

defense);

f. observation of Willow Flycatchers copulating (verifies 

attempted breeding);

g. flycatcher carrying nest material (verifies nesting attempt, 

but not nest outcome);

h. flycatcher carrying food or fecal sac (verifies nest with 

young, but not nest outcome);

i. locating an active nest (verifies nesting). Recall that 

general survey permits do not authorize nest searching or 

monitoring, and see section, “Special Considerations”;

j. observation of adult flycatchers feeding fledged young 

(verifies successful nesting).

You may be able to detect flycatcher nesting activity, 

especially once the chicks are being fed. Adults feed chicks at 

rates of as many as 30 times per hour, and the repeated trips 

to the nest tree or bush are often quite evident. Be sure to 

note on the flycatcher survey form any breeding activity that 

is observed, including detailed descriptions of the number of 

birds, and specific activities observed. Also note the location 

of breeding activities on an aerial photograph, map, or sketch 

of the area.

The number of flycatchers found at a site also can provide 

a clue as to whether they are migrants or territorial birds. Early 

season detections of single, isolated Willow Flycatchers often 

turn out to be migrants. However, discovery of a number of 

Willow Flycatchers at one site usually leads to verification 

that at least some of them remain as local breeders. This 

underscores the importance of completing a thorough survey 

of each site to be confident of the approximate number of 

flycatchers present.

In some cases, regardless of the time and diligence 

of your efforts, it will be difficult to determine the actual 

breeding status of a territorial male. In these instances, use 

your best professional judgment, or request the assistance of 

an experienced surveyor or an agency flycatcher coordinator to 

interpret your observations regarding breeding status. 

Reporting Results.—There is little value in conducting 

formal surveys if the data are not recorded and submitted. 

Fill in all appropriate information on the Willow Flycatcher 

survey form while still in the field, and mark the location of 

detections on a copy of the USGS topographic map. Make a 

habit of reviewing the form before you leave any site—trying 

to remember specific information and recording it later can 

lead to missing and inaccurate data. Note the location of 

the sighting on an aerial photograph or sketch of the site. 

Attaching photographs of the habitat also is useful. Whenever 

a Willow Flycatcher territory or nest site is confirmed, 

notify the USFWS or appropriate State wildlife agency as 

soon as you return from the field. The immediate reporting 

of flycatcher detections or nests may differ among USFWS 

regions and States—discuss these reporting procedures with 

your respective State and USFWS flycatcher coordinators.

Complete a survey form (appendix 1) for each site 

surveyed, whether or not flycatchers are detected. “Negative 

data” (that is, a lack of detections) are important to document 

the absence of Willow Flycatchers and help determine what 

areas have already been surveyed. Make and retain a copy of 

each survey form, and submit the original or a legible copy. 

Electronic copies of the survey forms also are acceptable and 

are available online (http://sbsc.wr.usgs.gov/cprs/research/

projects/swwf/). All survey forms must be submitted to 

the USFWS and the appropriate State wildlife agency by 

the specified deadline identified in your permits. Timely 

submission of survey data is a permit requirement, and will 

ensure the information is included in annual statewide and 

regional reports.
Section 2. Survey Protocol 25

Special Considerations

To avoid adverse impacts to Willow Flycatchers, follow 

these guidelines when performing all surveys:

1. Obtain all necessary Federal, State, and agency permits 

and permissions prior to conducting any surveys. Failure 

to do so leaves you liable for violation of the Endangered 

Species Act, various State laws, and prosecution for 

trespass.

2. Do not play the recording more than necessary or 

needlessly elicit vocal responses once Willow Flycatchers 

have been located and verified. This may distract 

territorial birds from caring for eggs or young, or 

defending their territory. If flycatchers are vocalizing upon 

arrival at the site, and your objective is to determine their 

presence or absence at a particular site—there is no need 

to play the recording. Excessive playing of the recording 

also may attract the attention of predators or brood 

parasites. Stop playing the survey recording as soon as 

you have confirmed the presence of a Willow Flycatcher, 

and do not play the recording again until you have moved 

30–40 m to the next survey location.

3. Proceed cautiously while moving through Willow 

Flycatcher habitat. Continuously check the area around 

you to avoid disturbance to nests of Willow Flycatchers 

and other species. Do not break understory vegetation, 

even dead branches, to create a path through the surveyed 

habitat.

4. Do not approach known or suspected nests. Nest searches 

and monitoring require specific State and Federal permits, 

have their own specialized methodologies (Rourke and 

others, 1999), and are not intended to be a part of this 

survey protocol. 

5. If you find yourself close to a known or suspected 

nest, move away slowly to avoid startling the birds or 

force‐fledging the young. Avoid physical contact with 

the nest or nest tree, to prevent physical disturbance and 

leaving a scent. Do not leave the nest area by the same 

route that you approached. This leaves a “dead end” trail 

that could guide a potential predator to the nest/nest tree. 

If nest monitoring is a component of the study, but you 

are not specifically permitted to monitor the nest, store a 

waypoint with your GPS, affix flagging to a nearby tree 

at least 10 m away, and record the compass bearing to the 

nest on the flagging. Report your findings to an agency 

flycatcher coordinator or a biologist who is permitted to 

monitor nests.

6. If you use flagging to mark an area where flycatchers are 

found, use it conservatively and make certain the flagging 

is not near an active nest. Check with the property owner 

or land-management agency before flagging to be sure 

that similar flagging is not being used for other purposes 

in the area. Unless conducting specific and authorized/

permitted nest monitoring, flagging should be placed no 

closer than 10 m to any nest. Keep flagging inconspicuous 

from general public view to avoid attracting people or 

animals to an occupied site, and remove it at the end of 

the breeding season.

7. Watch for and note the presence of potential nest 

predators, particularly birds, such as Common 

Ravens (Corvus corax), American Crows (Corvus 

brachyrhynchos), jays, and magpies. If such predators are 

in the immediate vicinity, wait for them to leave before 

playing the recording.

8. Although cowbird parasitism is no longer considered 

among the primary threats to flycatcher conservation it 

remains useful to note high concentrations of cowbirds 

in the comment section of the survey form. While 

conducting surveys, avoid broadcasting the flycatcher 

vocalizations if cowbirds are nearby, especially if you 

believe you may be close to an active flycatcher territory. 

The intent of not broadcasting flycatcher vocalizations 

is to reduce the potential for attracting cowbirds to a 

flycatcher territory or making flycatcher nests more 

detectable to cowbirds.

9. Non-indigenous plants and animals can pose a significant 

threat to flycatcher habitat and may be unintentionally 

spread by field personnel, including those conducting 

flycatcher surveys. Simple avoidance and sanitation 

measures can help prevent the spread of these organisms 

to other environments. To avoid being a carrier of 

non-indigenous plants or animals from one field site to 

another visually inspect and clean your clothing, gear, 

and vehicles before moving to a different field site. A 

detailed description on how to prevent and control the 

spread of these species is available by visiting the Hazard 

Analysis and Critical Control Point Planning for Natural 

Resource Management web site (http://www.haccp-nrm.

org). One species of particular interest is the tamarisk 

leaf-beetle (Diorhabda spp.). If you observe defoliation 

of saltcedar while conducting flycatcher surveys and 

believe that Diorhabda beetles may be responsible, notify 

your USFWS coordinator immediately. Other non-native 

species of concern in survey locations are the quagga 

mussel (Dreissena rostriformis bugensis), cheatgrass 

(Bromus tectorum), red brome (Bromus rubens), giant 

salvinia (Salvinia molesta), water milfoil (Myriophyllum 

spicatum), parrot’s feather (M. aquaticum), and amphibian 

chytrid fungus (Batrachochytrium dendrobatidis).
26 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

Acknowledgments

The authors’ work on this protocol was supported by 

the U.S. Geological Survey, the Bureau of Reclamation, 

and the U.S. Fish and Wildlife Service. We are indebted to 

numerous colleagues who over the years provided feedback 

on the previous survey protocols and helped shape this current 

revision; in particular we thank Allen Graber, William Haas, 

Tom Koronkiewicz, Barbara Kus, Henry Messing, Theresa 

Olson, Chuck Paradzick, Ruth Valencia, Mary Whitfield, and 

Sartor O. Williams, III. Greg Beatty, Peter Beck, Nathan 

Darnel, Robert Doster, Gjon Hazard, Ronald Kirby, Eben 

Paxton, Linda Sogge, and Leilani Takano provided helpful 

feedback on early drafts of this document. Eben Paxton 

also provided assistance with graphics. Revisions to the 

survey forms were a culmination of recommendations from 

many surveyors and data compilers. We especially thank 

Francoise Leonard, Shay Stump, Heather English, Barbara 

Kus, Scott Durst, Hira Walker, Greg Beatty, and Dave Moore 

for providing their insight from years of experience collecting 

data and interpreting field forms. We are especially grateful to 

Greg Beatty for his support of our efforts and for the key role 

he has played in helping standardize Southwestern Willow 

Flycatcher survey efforts across the Southwest.

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Sferra, S.J., Corman, T.E., Paradzick, C.E., Rourke, J.W., 

Spencer, J.A., and Sumner, M.W., 1997, Arizona Partners in 

Flight Southwestern Willow Flycatcher survey—1993–1996 

summary report: Nongame and Endangered Wildlife 

Program Technical Report 113, Arizona Game and Fish 

Department, Phoenix, Arizona, 46 p.

Shook, R.S., Stoleson, S.H., and Boucher, P., 2003, A field 

evaluation of the Southwestern Willow Flycatcher survey 

protocol: Studies in Avian Biology, v. 26, p. 177-179.

Siegle, R., and Ahlers, D., 2004, Brown-headed Cowbird 

management techniques manual: Techniques Manual by the 

Bureau of Reclamation, Technical Service Center, Denver, 

Colorado.

Sogge, M.K., Koronkiewicz, T.J.; van Riper, C., and Durst, 

S.L., 2007a, Willow Flycatcher nonbreeding territory 

defense behavior in Costa Rica: Condor, v. 109, p. 475-480.

Sogge, M.K., Kus, B.E., Sferra, S.J., and Whitfield, 

M.J., 2003b, Ecology and conservation of the Willow 

Flycatcher—Studies in Avian Biology 26: Cooper 

Ornithological Society, Camarillo, CA, 210 p.

Sogge, M.K., and Marshall, R.M., 2000, Chapter 5: A 

survey of current breeding habitats, in Finch, D.M., and 

Stoleson, S.H., eds., Status, ecology, and conservation of 

the Southwestern Willow Flycatcher: U.S. Forest Service 

Rocky Mountain Research Station General Technical 

Report-60, p. 43-56.

Sogge, M.K., Marshall, R.M., Tibbitts, T.J., and Sferra, S.J. 

1997a, A Southwestern Willow Flycatcher natural history 

summary and survey protocol: National Park Service 

Technical Report NPS/NAUCPRS/NRTR-97/12, 37 p.

Sogge, M.K., Paxton, E.H., and Tudor, A.A., 2006, Saltcedar 

and Southwestern Willow Flycatchers: lessons from 

long-term studies in central Arizona, in Aguirre-Bravo, 

C., Pellicane, P.J., Burns, D.P., and Draggan, S., eds., 

Monitoring science and technology symposium: unifying 

knowledge for sustainability in the Western hemisphere: 

September 20-24, 2004, Denver, Colorado: Proceedings 

RMRS-P-42CD, U.S. Department of Agriculture, Forest 

Service, Rocky Mountain Research Station, Fort Collins, 

Colorado, p. 238–241.

Sogge, M.K., Sferra, S.J., McCarthey, T.D., Williams, S.O., 

and Kus, B.E., 2003a, Distribution and characteristics 

of Southwestern Willow Flycatcher breeding sites and 

territories: Studies in Avian Biology, v. 26, p. 5-11.

Sogge, M.K., Sferra, S.J., and Paxton, E.H., 2008, Saltcedar as 

habitat for birds—Implications to riparian restoration in the 

Southwest: Restoration Ecology, v. 16, p. 146-154.

Sogge, M.K., Tibbitts, T.J., and Petterson, J., 1997a, Status and 

breeding ecology of the Southwestern Willow Flycatcher in 

the Grand Canyon: Western Birds, v. 28, p. 142-157.

Sogge, M.K., Tibbitts, T.J., van Riper, C., and May, T., 1995, 

Status of the Southwestern Willow Flycatcher along the 

Colorado River in Grand Canyon National Park—1995, 

Summary report: National Biological Service Colorado 

Plateau Research Station/Northern Arizona University, 26 p.

Spencer, J.A., Sferra, S.J., Corman, T.E., Rourke, J.W., and 

Sumner, M.W., 1996, Arizona Partners in Flight 1995 

Southwestern Willow Flycatcher survey: Nongame and 

Endangered Wildlife Program Technical Report 79, Arizona 

Game and Fish Department, Phoenix, Arizona, 46 p.

State of Arizona, 1990, Final report and recommendations 

of the Governor’s riparian habitat task force, Executive 

Order 89-16: Streams and riparian resources, Phoenix, 

Arizona, October 1990, 28 p. 

Stein, R.C., 1963, Isolating mechanisms between populations 

of Traill’s Flycatchers: Proceedings of the American 

Philosophical Society, v. 107, no. 1, p. 21-50.

Stoleson, S.H., and Finch, D.M., 2003, Microhabitat use by 

breeding Southwestern Willow Flycatchers on the Gila 

River, NM: Studies in Avian Biology, v. 26, p. 91-95.

Stoleson, S.H., Whitfield, M.J., and Sogge, M.K., 2000, 

Chapter 8: Demographic characteristics and population 

modeling, in Finch D.M., and Stoleson, S.H., eds., Status, 

ecology, and conservation of the Southwestern Willow 

Flycatcher: U.S. Forest Service Rocky Mountain Research 

Station General Technical Report-60, p. 84-94.

Tibbitts, T.J., Sogge, M.K., and Sferra, S.J., 1994, A 

survey protocol for the Southwestern Willow Flycatcher 

(Empidonax traillii extimus): National Park Service 

Technical Report NPS/NAUCPRS/NRTR-94/04.

Unitt, P., 1987, Empidonax traillii extimus: an endangered 

subspecies: Western Birds, v. 18, no. 3, p. 137-162. 

U.S. Fish and Wildlife Service, 1991, Notice of review: 

animal candidate review for listing as endangered or 

threatened species, November 21, 1991: Federal Register 

56:58804-58836. 

U.S. Fish and Wildlife Service, 1993, Proposal to list the 

Southwestern Willow Flycatcher as an endangered species 

and to designate critical habitat, July 23, 1993: Federal 

Register 58:39495-39522. 

U.S. Fish and Wildlife Service, 1995, Final Rule Determining 

Endangered Status for the Southwestern Willow Flycatcher: 

Federal Register 60:10694 (February 27, 1995).
30 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

U.S. Fish and Wildlife Service, 1997, Final determination 

of critical habitat for the Southwestern Willow 

Flycatcher (Empidonax traillii extimus): Federal Register 

62(140):39129-39147.

U.S. Fish and Wildlife Service, 2002, Southwestern Willow 

Flycatcher (Empidonax traillii extimus) final recovery plan: 

U.S. Fish and Wildlife Service, Albuquerque, New Mexico.

U.S. Fish and Wildlife Service, 2005, Designation of critical 

habitat for the Southwestern Willow Flycatcher (Empidonax 

traillii extimus), Final Rule: Federal Register 70:60886–

61009 (October 19, 2005).

Utah Division of Wildlife Resources, 1997, Utah Sensitive 

Species List – March 1997: Utah Division of Wildlife 

Resources, Salt Lake City, Utah, 28 p.

Whitfield, M.J., 1990, Willow Flycatcher reproductive 

response to brown-headed cowbird parasitism: Chico, 

California, California State University, Masters theses, 25 p. 

Whitfield, M.J., and Enos, K., 1996, A Brown-headed Cowbird 

control program and monitoring for the Southwestern 

Willow Flycatcher, South Fork Kern River, California, 

1996: Report to the U.S. Army Corps of Engineers, 

Sacramento District and the California Department of Fish 

and Game. 

Whitfield, M.J., and Sogge, M.K., 1999, Range-wide impacts 

of Brown-headed Cowbird parasitism on the Southwestern 

Willow Flycatcher (Empidonax traillii extimus), 1999: 

Studies in Avian Biology, v. 18, p. 182-190.

Whitfield, M.J., and Strong, C.M., 1995, A Brown-headed 

Cowbird control program and monitoring for the 

Southwestern Willow Flycatcher, South Fork Kern River, 

California: California Department of Fish and Game, 

Bird and Mammal Conservation Program Report 95-4, 

Sacramento, California, 17 p.

Wiesenborn, W.D., and Heydon, S.L., 2007, Diet of 

Southwestern Willow Flycatcher compared among breeding 

populations in different habitats: Wilson Journal of 

Ornithology, v. 119, p. 547–557.

Wilbur, S.R., 1987, Birds of Baja California: Berkeley, 

California, University of California Press. 

Yard, H.K., and Brown, B.T., 1999, Willow Flycatcher nest 

resuse in Arizona: Journal of Field Ornithology, v. 70, 

p. 211–213. 

Yard, H.K., and Brown, B.T., 2003, Singing behavior of the 

Southwestern Willow Flycatchers in Arizona: Studies in 

Avian Biology, v. 26, p. 125–130. 
Appendix 1 31

 Willow Flycatcher (WIFL) Survey and Detection Form (revised April 2010)

Site Name__________________________________________________ State______ County ___________________________ 

USGS Quad Name ____________________________________________ Elevation _______________________ (meters) 

Creek, River, Wetland, or Lake Name________________________________________________________________________ 

Is copy of USGS map marked with survey area and WIFL sightings attached (as required)? Yes___ No____ 

Survey Coordinates: Start: E___________________ N_______________________ UTM Datum_______(See instructions) 

 Stop: E___________________ N_______________________ UTM Zone ________ 

If survey coordinates changed between visits, enter coordinates for each survey in comments section on back of this page. 

** Fill in additional site information on back of this page **

Survey # 

Observer(s) 

(Full Name)

Date (m/d/y) 

Survey time 

Number 

of Adult 

WIFLs 

Estimated 

Number of 

 Pairs 

Estimated 

Number of 

Territories

Nest(s) Found?

Y or N 

If Yes, number 

of nests 

Comments (e.g., bird behavior; 

evidence of pairs or breeding; 

potential threats [livestock, 

cowbirds, Diorhabda spp.]). If 

Diorhabda found, contact 

USFWS and State WIFL 

coordinator 

GPS Coordinates for WIFL Detections 

(this is an optional column for documenting 

individuals, pairs, or groups of birds found on 

each survey). Include additional sheets if 

necessary. 

# Birds Sex UTM E UTM N 

 

 

 

 

Survey # 1 

Observer(s) Date

Start 

Stop 

Total hrs ___ 

# Birds Sex UTM E UTM N 

 

 

 

 

Survey # 2 

Observer(s)

Date

Start 

Stop 

Total hrs ___ 

# Birds Sex UTM E UTM N 

 

 

 

 

Survey # 3 

Observer(s) Date

Start 

Stop 

Total hrs ___ 

# Birds Sex UTM E UTM N

 

 

 

 

Survey # 4 

Observer(s) Date

Start 

Stop 

Total hrs ___ 

# Birds Sex UTM E UTM N 

 

 

 

 

Survey # 5 

Observer(s) Date

Start 

Stop 

Total hrs ___ 

Total 

Adult 

Residents 

Total 

Pairs 

Total 

Territories

Total 

Nests 

Overall Site Summary 

Totals do not equal the sum of 

each column. Include only 

resident adults. Do not include 

migrants, nestlings, and 

fledglings. 

Be careful not to double count 

individuals. 

Total Survey Hrs________

 

Were any Willow Flycatchers color-banded? Yes___ No ___ 

If yes, report color combination(s) in the comments 

section on back of form and report to USFWS. 

Reporting Individual _____________________________________ Date Report Completed________ ____________________ 

US Fish and Wildlife Service Permit #________________________State Wildlife Agency Permit #________________________ 

Submit form to USFWS and State Wildlife Agency by September 1st. Retain a copy for your records.

Appendix 1. Willow Flycatcher Survey and Detection Form

Always check the U.S. Fish and Wildlife Service Arizona Ecological Services Field Office web site (http://www.fws.gov/

southwest/es/arizona/) for the most up-to-date version. 
32 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

Fill in the following information completely. Submit form by September 1st. Retain a copy for your records.

Reporting Individual __________________________________________________Phone # __________________________

Affiliation __________________________________________________________ E-mail ___________________________

Site Name___________________________________________________________Date Report Completed ______________

Did you verify that this site name is consistent with that used in previous years? Yes ____ No _____ Not Applicable ___

If site name is different, what name(s) was used in the past?________________________________________________________

If site was surveyed last year, did you survey the same general area this year? Yes ____ No ____ If no, summarize below.

Did you survey the same general area during each visit to this site this year? Yes ____ No ____ If no, summarize below.

Management Authority for Survey Area : Federal____ Municipal/County ____ State ____ Tribal ____ Private ____

Name of Management Entity or Owner (e.g., Tonto National Forest) _______________________________________________

Length of area surveyed: ___________ (meters)

Vegetation Characteristics: Mark the category that best describes the predominant tree/shrub foliar layer at this site (check one):

_____ Native broadleaf plants (entirely or almost entirely, > 90% native, includes high-elevation willow)

_____ Mixed native and exotic plants (mostly native, 50 - 90% native)

_____ Mixed native and exotic plants (mostly exotic, 50 - 90% exotic)

_____ Exotic/introduced plants (entirely or almost entirely, > 90% exotic)

Identify the 2-3 predominant tree/shrub species in order of dominance. Use scientific name. 

_______________________________________________________________________________________________________

Average height of canopy (Do not include a range): _______________________________ (meters)

Attach copy of USGS quad/topographical map (REQUIRED) of survey area, outlining survey site and location of WIFL detections. 

Attach sketch or aerial photo showing site location, patch shape, survey route, location of any WIFLs or WIFL nests detected. 

Attach photos of the interior of the patch, exterior of the patch, and overall site; describe any unique habitat features.

Comments (attach additional sheets if necessary)

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

_______________________________________________________________________________________________________

Territory Summary Table. Provide the following information for each verified territory at your site.

Attach additional sheets if necessary

Territory

Number

All Dates

Detected 

UTM N UTM E Pair 

Confirmed?

Y or N

Nest 

Found?

Y or N

Description of How You Confirmed 

Territory and Breeding Status

(e.g., vocalization type, pair interactions, 

nesting attempts, behavior)
Appendix 2 33

Appendix 2. Willow Flycatcher Survey Continuation Sheet / Territory Summary 

Table

Always check the U.S. Fish and Wildlife Service Arizona Ecological Services Field Office web site (http://www.fws.gov/

southwest/es/arizona/) for the most up-to-date version. 

Willow Flycatcher Survey Continuation Sheet 

(For reporting additional detections and territories; append to Survey and Detection form) 

 Reporting Individual __________________________________________________Phone # __________________________ 

 Affiliation __________________________________________________________ E-mail ___________________________ 

 Site Name___________________________________________________________Date Report Completed ______________ 

Territory 

Number 

All Dates 

Detected UTM E UTM N 

Pair 

Confirmed? 

Y or N 

Nest 

Found? 

Y or N 

Description of How You Confirmed Territory 

and Breeding Status (e.g., vocalization type, pair 

interactions, nesting attempts, behavior) 

 

 

 

 

 

 

 

Comments____________________________________________________________________________________________

_____________________________________________________________________________________________________

_____________________________________________________________________________________________________

_____________________________________________________________________________________________________

_____________________________________________________________________________________________________

_____________________________________________________________________________________________________

_____________________________________________________________________________________________________

_____________________________________________________________________________________________________

_____________________________________________________________________________________________________

_____________________________________________________________________________________________________

_____________________________________________________________________________________________________

_____________________________________________________________________________________________________

_____________________________________________________________________________________________________

_____________________________________________________________________________________________________

_____________________________________________________________________________________________________

_____________________________________________________________________________________________________

_____________________________________________________________________________________________________

_____________________________________________________________________________________________________

_____________________________________________________________________________________________________ 
34 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

These instructions are provided as guidance for completing the 

standard survey form. It is particularly important to provide the 

correct type and format of information for each field. Complete 

and submit your survey forms to both the appropriate State 

Willow Flycatcher coordinator and the U.S. Fish and Wildlife 

Service (USFWS) by September 1 of the survey year. You also 

may complete forms digitally (Microsoft© Word or Excel) and 

submit them via email with attached or embedded topographic 

maps and photographs.

Page 1 of Survey Form

Site Name. Standardized site names are provided by the 

flycatcher survey coordinators for each State and should be 

consistent with the naming of other sites that might be in the area. 

If the site is new, work with your State or USFWS flycatcher 

coordinator to determine suitable site names before the beginning 

of the survey season. If the site was previously surveyed, use the 

site name from previous years (which can be obtained from the 

State or USFWS flycatcher coordinator). If you are uncertain if 

the site was previously surveyed, contact your State or USFWS 

flycatcher coordinator.

USGS Quad Name. Provide the full quad name, as shown on the 

appropriate standard 7.5-minute topographic maps.

Creek, River, Wetland, or Lake Name. Give the name of the 

riparian feature, such as the lake or watercourse, where the survey 

is being conducted. 

Survey Coordinates. Provide the start and end points of the 

survey, which will indicate the linear, straight-line extent of 

survey area, based on Universal Transverse Mercator coordinates 

(UTMs). California surveyors only: provide latitude/longitude 

geographic coordinates instead of UTMs in the UTM fields and 

identify them as such. If the start and end points of the survey 

changed significantly among visits, enter separate coordinates for 

each survey in the comments section on the back of the survey 

sheet. Note that we do not need the coordinates for the detailed 

path taken by the surveyor(s). 

Datum. Indicate the datum in which the coordinates are 

expressed: NAD27, WGS84, or NAD83. The datum can be found 

in the settings of most GPS units. Note that Arizona prefers 

NAD27 and New Mexico prefers NAD83. 

Zone. Provide the appropriate UTM zone for the site, which is 

displayed along with the coordinates by most GPS units. Zones 

for California are 10, 11, or 12. The zone for Arizona is 12. Zones 

for New Mexico are 12 or 13.

Survey #. Survey 1 – 5. See the protocol for an explanation of the 

number of required visits for each survey period. Note: A survey 

is defined as a complete protocol-based survey that occurs over 

no more than 1 day. If a site is so large as to require more than 

a single day to survey, consider splitting the site into multiple 

subsites and use separate survey forms for each. Casual site visits, 

pre-season or supplemental visits, or follow-up visits to check on 

the status of a territory should not be listed in this column, but 

should be documented in the Comments section on page 2 or in 

the survey continuation sheet. 

Date. Indicate the date that the survey was conducted, using the 

format mm/dd/yyyy.

Start and Stop. Start and stop time of the survey, given in 

24-hour format (e.g., 1600 hours rather than 4:00 p.m.).

Total hours. The duration of time (in hours) spent surveying the 

site, rounded to the nearest tenth (0.1) hour. For single-observer 

surveys, or when multiple observers stay together throughout 

the survey, total the number of hours from survey start to end. If 

two or more observers surveyed sections of the site concurrently 

and independently, sum the number of hours each observer spent 

surveying the site. 

Number of Adult WIFLs. The total number of individual adult 

Willow Flycatchers detected during this particular survey. Do not 

count nestlings or recently fledged birds. 

Number of Pairs. The number of breeding pairs. Do not assume 

that any bird is paired; designation of birds as paired should be 

based only on direct evidence of breeding behaviors described 

in the protocol. If there is strong evidence that the detected bird 

is unpaired, enter “0”. If it is unknown whether a territorial bird 

is paired, enter “–”. Note that the estimated number of pairs can 

change over the course of a season.

Number of Territories. Provide your best estimate of the number 

of territories, defined as a discrete area defended by a resident 

single bird or pair. This is usually evidenced by the presence of 

a singing male, and possibly one or more mates. Note that the 

estimated number of territories may change over the course of a 

season.

Nest(s) Found? Yes or No. If yes, indicate the number of nests. 

Renests are included in this total.

Comments about this survey. Describe bird behavior, evidence 

of pairs or breeding, evidence of nest building, evidence of 

nestlings/fledglings, nesting, vocalizations (e.g., interaction 

twitter calls, whitts, britts, wheeos, fitz-bews/countersinging), 

potential threats (e.g., livestock, cowbirds, saltcedar leaf beetles 

[Diorhabda spp.] etc.). If Diorhabda beetles are observed, contact 

your USFWS and State flycatcher coordinator immediately. 

Please be aware that permits are needed for nest monitoring.

GPS Coordinates for WIFL Detections. Provide the number 

of birds (e.g., unpaired, paired, or groups of birds) and 

corresponding UTMs. If known, provide the sex of individuals.

Overall Site Summary. For each of these columns, provide your 

best estimate of the overall total for the season. Do not simply 

total the numbers in each column. In some cases where consistent 

numbers were detected on each survey, the overall summary is 

easy to determine. In cases where numbers varied substantially 

among the different surveys, use professional judgment and logic 

to estimate the most likely number of adults, pairs, and territories 

that were consistently present. Be careful not to double count 

individuals. Record only territorial adult Southwestern Willow 

Flycatchers, do not include migrants, nestlings, or fledglings in 

the overall summary. In complex cases, consult with your State 

or USFWS flycatcher coordinator.

Appendix 3. Instructions for Completing the Willow Flycatcher Survey and 

Detection Form and the Survey Continuation Sheet
Appendix 3 35

Total Survey Hours. The sum of all hours spent surveying the 

site.

Were any WIFLs color-banded? Circle or highlight “Yes” 

or “No”. If yes, report the sighting and color combination (if 

known) in the comments section on back of form, and contact 

your USFWS coordinator within 48 hours after returning from the 

survey. Note that identifying colors of bands is difficult and might 

require follow-up visits by experienced surveyors. 

Reporting Individual. Indicate the full first and last name of the 

reporting individual.

Date Report Completed. Provide the date the form was 

completed in mm/dd/yyyy format.

U.S. Fish and Wildlife Service Permit #. List the full number 

of the required federal permit under which the survey was 

completed.

State Wildlife Agency Permit #. If a State permit is required 

by the State in which the survey was completed, provide the full 

number of the State permit. State permits are required for Arizona 

and California. State permits are recommended for New Mexico.

Page 2 of Survey Form

Affiliation. Provide the full name of the agency or other 

affiliation (which is usually the employer) of the reporting 

individual.

Phone Number. Self-explanatory; include the area code.

E-mail. Self-explanatory.

Was this site surveyed in a previous year? Indicate “Yes”, 

“No”, or “Unknown.”

Did you verify that this site name is consistent with that 

used in previous years? Indicate “Yes” or “No”. This can be 

determined by checking survey forms from previous years or 

consulting with agency flycatcher coordinators.

If site name is different, what name(s) was used in the past?

Enter the full site name that was used in previous years.

If site was surveyed last year, did you survey the same general 

area this year? Indicate “Yes” or “No”. If no, indicate the reason 

and how the survey varied in the Comments section.

Did you survey the same general area during each visit to 

this site this year? If no, indicate the reason in the Comments 

section and delineate the differing route of each survey on the 

topographical map. 

Management Authority for Survey Area. Mark the appropriate 

management authority.

Name of Management Entity or Owner (e.g., Tonto National 

Forest). Provide the name of the organization or person(s) 

responsible for management of the survey site. 

Length of area surveyed. Estimate the linear straight-line 

distance of the length of the area surveyed, in kilometers. This is 

not an estimate of the total distance walked throughout the survey 

site. Do not provide a range of distances.

Vegetation Characteristics: Mark only one of the categories that 

best describes the predominant tree/shrub foliar layer at the site. 

Native broadleaf habitat is composed of entirely or almost 

entirely (i.e., > 90%) native broadleaf plants.

Mostly native habitat is composed of 50–90% native plants with 

some (i.e., 10–50%) non-native plants.

Mostly exotic habitat is composed of 50–90% non-native plants 

with some (i.e., 10–50%) native plants.

Exotic/introduced habitat is composed entirely or almost entirely 

(i.e., > 90%) of non-native plants.

Identify the 2–3 predominant tree/shrub species in order of 

dominance. Identify by scientific name. 

Average height of canopy. Provide the best estimate of the 

average height of the top of the canopy throughout the patch. 

Although canopy height can vary, give only a single (not a range) 

overall height estimate.

Attach the following: (1) copy of USGS quad/topographical 

map (REQUIRED) of survey area, outlining survey site 

and location of WIFL detections; (2) sketch or aerial photo 

showing site location, patch shape, survey route, location 

of any detected WIFLs or their nests; (3) photos of the 

interior of the patch, exterior of the patch, and overall site. 

Describe any unique habitat features in Comments. Include 

the flycatcher territory number and GPS location. You also may 

include a compact disc of photographs.

Comments. Include any information that supports estimates of 

total territory numbers and breeding status. You may provide 

additional information on bird behavior, banded birds, evidence 

of pairs or breeding, nesting, potential threats (e.g., livestock, 

cowbirds, saltcedar leaf beetles [Diorhabda spp.] etc.), and 

changes in survey length and route throughout the season. Attach 

additional pages or use the continuation sheet if needed.

Table. If Willow Flycatchers are detected, complete the table at 

the bottom of the form. Identify flycatchers by territory number 

and include the dates detected, UTMs, whether or not pairs were 

detected, and whether or not nests were located. Also describe the 

observation. For example, the surveyor might have observed and 

heard a bird fitz-bew from an exposed perch, heard and observed 

two birds interacting and eliciting a twitter call, heard a bird 

fitz-bew while observing another carrying nesting material, heard 

birds from territory 1 and 2 countersinging, etc. This information 

provides supporting information for territory and breeding status. 

Use the continuation sheet if needed.
36 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher

Appendix 4. Example of a Completed Willow Flycatcher Survey and Detection 

Form (with map)

Site Name: State: County:

Elevation:

X No

Start: E N UTM Datum:

Stop: E N UTM Zone:

Nest(s)

Found?

Y or N

If Yes, 

number of 

nests

Survey # 1 # Birds Sex UTM N

Observer(s): 1 M 3,714,926

D. Savage 1 M 3,714,628

1 M 3,714,778

1 M 3,715,009

1 M 3,714,732

Survey # 2 # Birds Sex UTM N

Observer(s): 1 M 3,714,926

S. Kennedy 1 M 3,714,628

2 M/F 714,778

2 M/F 3,715,009

2 M/F 3,714,732

2 M/F 3,714,640

1 M 3,714,524

Survey # 3 # Birds Sex UTM N

Observer(s): 1 M 3,714,926

S. Kennedy 1 M 3,714,628

2 M/F 3,714,778

2 M/F 3,715,009

2 M/F 3,714,732

2 M/F 3,714,640

2 M/F 3,714,524

Survey # 4 # Birds Sex UTM N

Observer(s): 1 M 3,714,926

D. Moore 1 M 3,714,628

2 M/F 3,714,778

2 M/F 3,715,009

2 M/F 3,714,732

2 M/F 3,714,640

2 M/F 3,714,524

Survey # 5 # Birds Sex UTM N

Observer(s): 1 M 3,714,628

D. Moore 2 M/F 3,714,778

2 M/F 3,715,009

2 M/F 3,714,732

2 M/F 3,714,640

2 M/F 3,714,524

Yes No X

21.8

Start:

6:00

Stop: 4

UTM E

UTM E

305,276

305,084

306,009

304,339

**Fill in additional site information on back of this page**

Suitable breeding habitat dispersed throughout site. 

WIFLs were very vocal, and covering large areas.

No obvious signs of pairing were observed.

Approximately 10 head of cattle were found within 

this site.

UTM E

305,131

305,191

Stop: 305,394

 Is copy of USGS map marked with survey area and WIFL sightings attached (as required)? Yes

Creek, River, or Lake Name: Rio Grande

If survey coordinates changed between visits, enter coordinates for each survey in comments section on back of this page.

3,715,506 (See instructions)

3,711,922

Survey Coordinates: NAD 83

13

Date:

Y (3)

Stop:

Stop:

Site is no longer flooded, but saturated soils persist 

throughout most of site. No change in territory 

numbers or status. All SWFL pairs very quiet - 

only a few whits and fitz-bews. Light rain over 

night, vegetation was saturated early in the morning.

Lots of mosquitos!

Site beginning to dry out, some portions still 

muddy. One of the unpaired males could not be 

detected. It was hard to hear SWFLs due to breezy 

conditions early in the morning.

305,084

305,191

305,394

Were any WIFLs color-banded?

Date:

5:30

10:00

5:30

Stop:

10:00

Start:

4.5

305,191

305,394

305,084

305,001

10:15

Total hrs:

Start:

Date:

5

Total hrs:

11

7/1/2009 305,276

5

10:00

305,394

7 Y (4)

305,010

305,001

305,131

305,191

305,394

305,001

305,010

UTM E

305,084

Willow Flycatcher (WIFL) Survey and Detection Form (revised April, 2010)

Paraje Well 1,356

Socorro

USGS Quad Name:

DL-08

(meters)

7

Portions of site still flooded. All territories found in 

Survey 2 are still active. The two males found 

during Surveys #1 and #2, still believed to be 

unpaired. All other territories are believed to be 

paired. Several cows observed in vicinity of active 

territories.

305,276

305,131

305,191

305,001

305,010

Portions of site are flooded, 1-2 ft deep. Two males 

found during 1st survey appear unpaired. Three 

pairs confirmed based on nesting, and another pair 

suspected based on vocal interactions and 

nonaggressive behavior with another flycatcher.

Two additional territories (1 pair and 1 unpaired 

male) found during this survey.

305,131

Total hrs:

Start:

Y (4)

4.5

N

4.3

6/10/2009

4.5

6/21/2009

11

12 7

5/24/2009

Be careful not to double count 

individuals.

Overall Site Summary

Totals do not equal the sum of each 

column. Include only resident adults.

Do not include migrants, nestlings, and 

fledglings.

Start:

5:45

10:15

Total hrs:

New Mexico

State Wildlife Agency Permit #:

Date Report Completed:

Submit form to USFWS and State Wildlife Agency by September 1st. Retain a copy for your records.

0 5

5

5

7/10/2009

12

Total Adult 

Residents Total Pairs Total

Territories

Total hrs:

6:00

Reporting Individual: Darrell Ahlers 8/20/2009

US Fish & Wildlife Service Permit #: TE819475-2 N/A

4 If yes, report color combination(s) in the comments

section on back of form and report to USFWS.

4.0

Date:

6

Total Nests

Y (4)

UTM E

305,131

305,010

Total survey hrs: 12 5 7

305,276

Survey #

Observer(s)

(Full Name)

Date (m/d/y) 

Survey Time 

Number of 

Adult

WIFLs

Estimated

Number of 

Pairs

Estimated

Number of 

Territories

Comments (e.g., bird behavior; evidence of pairs or 

breeding; potential threats [livestock, cowbirds, 

Diorhabda spp.]). If Diorhabda found, contact 

USFWS and State WIFL coordinator.

GPS Coordinates for WIFL Detections

(this is an optional column for documenting individuals, 

pairs, or groups of birds found on 

each survey). Include additional sheets if necessary.

Date:

305,084
Appendix 4 37

Phone #

Affiliation E-mail

Site Name

Yes x No

Yes x No

Yes x No

Federal X Municipal/County State Tribal Private

Length of area surveyed: 

X

(meters)

Nest Found? 

Y or N

N

N

Y

Y

Y

Y

N

3,714,732

3,714,640

3,714,524

Was this site surveyed in a previous year? Yes__x__ No____ Unknown____

Vegetation Characteristics: Check (only one) category that best describes the predominant tree/shrub foliar layer at this site:

UTM N

3,714,926

3,714,628

3,714,778

N extended presence at site from 5/24 through 7/10, 

no evidence of pairing 2 (Unpaired male) 5/24, 6/10,6/21,7/1, 7/10 305,131

 Pair confirmed based on vocalizations and 

observation of unchallenged WIFL

4 (Pair w/nest) 5/24, 6/10,6/21,7/1, 7/10 Y

3 (Pair) 5/24, 6/10,6/21,7/1, 7/10 305,191 Y

6/10,6/21,7/1, 7/10 305,001

305,084

6 (Pair w/nest)

(303) 445-2233

Confirmed breeding status with nest

Y Confirmed breeding status with nest

6

If no, summarize below.

Bureau of Reclamation

If site was surveyed last year, did you survey the same general area this year? 

Did you survey the same general area during each visit to this site this year? 

Mixed native and exotic plants (mostly exotic, 50 - 90% exotic)

Attach additional sheets if necessary

7 (Pair w/nest) 6/10,6/21,7/1, 7/10 305,010 Y

Reporting Individual

Identify the 2-3 predominant tree/shrub species in order of dominance. Use scientific name.

Salix Gooddingii, Populus spp., Tamarix spp.

Not Applicable

Management Authority for Survey Area:

Average height of canopy (Do not include a range): 

If name is different, what name(s) was used in the past? 

Territory Summary Table. Provide the following information for each verified territory at your site.

If no, summarize below.

Attach the following: 1) copy of USGS quad/topographical map (REQUIRED) of survey area, outlining survey site and location of WIFL detections;

8/20/2009

dahlers@usbr.gov

Date report Completed

Bureau of Reclamation

Confirmed breeding status with nest

305,394

Description of How You Confirmed

Territory and Breeding Status

(e.g., vocalization type, pair interactions, 

nesting attempts, behavior)

Territory Number UTM E

Pair

Confirmed?

Y or N

5 (Pair w/nest) 5/24, 6/10,6/21,7/1, 7/10

3,715,009 Confirmed breeding status with nest

Y

2) sketch or aerial photo showing site location, patch shape, survey route, location of any detected WIFLs or their nests; 

305,276 N extended presence at site from 5/24 through 7/1, no 

evidence of pairing 1 (Unpaired male)

All Dates Detected

Comments (such as start and end coordinates of survey area if changed among surveys, supplemental visits to sites, unique habitat features. 

Attach additional sheets if necessary.

3) photos of the interior of the patch, exterior of the patch, and overall site. Describe any unique habitat features in Comments.

Great habitat with saturated or flooded soils throughout most of the site on 1st survey. Site began to dry by the end of the breeding season. SWFL 

territories are dominated by Gooddings willow, however Tamarix spp. tends to be increasing in density compared to previous years. Site is supported 

by flows from the Low Flow Conveyance Channel.

5/24, 6/10,6/21,7/1

Exotic/introduced plants (entirely or almost entirely, > 90% exotic)

DL-08

Darrell Ahlers

2.5 (km)

Native broadleaf plants (entirely or almost entirely, > 90% native)

Mixed native and exotic plants (mostly native, 50 - 90% native)

Did you verify that this site name is consistent with that used in previous yrs?

Not applicable

Name of Management Entity or Owner (e.g., Tonto National Forest)

Fill in the following information completely. Submit form by September 1 st . Retain a copy for your records.
38 A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher
Publishing support provided by the U.S. Geological Survey

Publishing Network, Tacoma Publishing Service Center

For more information concerning the research in this report, contact

 Mark Sogge

U.S. Geological Survey

2255 Gemini Drive, 

Flagstaff, AZ 86001
Sogge and others— A Natural History Summary and Survey Protocol for the Southwestern Willow Flycatcher—Techniques and Methods 2A-10