A Southwestern Willow Flycatcher Natural History Summary ......A Southwestern Willow Flycatcher...

National Park Service Colorado Plateau Research Station

U.S. Department of the Interior at Northern Arizona University

A Southwestern Willow FlycatcherNatural History Summary and Survey Protocol

Technical Report NPS/NAUCPRS/NRTR-97/12

Mark K. SoggeUSGS Colorado Plateau Research Station/Northern Arizona University

Robert M. MarshallU.S. Fish and Wildlife Service, Phoenix, AZ

Susan J. SferraArizona Game and Fish Department, Phoenix, AZ

Timothy J. TibbittsNational Park Service, Organ Pipe National Monument, AZ

May 1997

List of Figures ................................................................................................................................................ v

List of Tables .................................................................................................................................................. v

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

Section I: Natural History ............................................................................................................................. 3

Breeding Range and Taxonomy .......................................................................................................... 3

Migration and Winter Range ............................................................................................................... 3

Habitat ................................................................................................................................................... 4

Breeding Chronology and Biology................................................................................................... 13

Nests and Eggs......................................................................................................................... 14

Site Fidelity and Persistence................................................................................................... 15

Threats to the Flycatcher and Habitat .................................................................................... 15

Section II: The Survey Protocol ................................................................................................................. 17

Permits ................................................................................................................................................ 18

Pre-survey Preparation ..................................................................................................................... 18

Equipment ........................................................................................................................................... 19

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

Physical Description ................................................................................................................ 19

Vocalizations ............................................................................................................................. 20

Special Considerations............................................................................................................ 20

Timing and Number of Visits ............................................................................................................ 21

Survey 1: 15-31 May ................................................................................................................ 21

Survey 2: 1-21 June ................................................................................................................. 21

Survey 3: 22 June-10 July ...................................................................................................... 22

Survey Methods ................................................................................................................................. 23

Documenting Presence/Absence ........................................................................................... 23

Looking for and Recording Color Bands ............................................................................... 24

Determining the Number of Territories and Pairs ................................................................. 25

Determing Breeding Status ..................................................................................................... 25

Documenting Presence of Cowbirds ..................................................................................... 26

Reporting Results .................................................................................................................... 27

Acknowledgments ....................................................................................................................................... 28

Contacts .................................................................................................................................................... 29

Literature Cited ............................................................................................................................................ 31

Appendix 1: Willow Flycatcher Survey and Detection Form (rev. 4/97) ................................................ 37

TABLE OF CONTENTS

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Figure 1. Breeding ranges of the willow flycatcher subspecies. ............................................................. 3

Figure 2. Willow flycatcher breeding and wintering ranges. .................................................................... 4

Figure 3. Examples of some of the variation in southwestern willow flycatcher breeding habitat.

Figure 3a. Little Colorado River, AZ .................................................................................................. 7

Figure 3b. Little Colorado River, AZ.................................................................................................. 7

Figure 3c. Tonto Creek, AZ ................................................................................................................. 7

Figure 3d. Rio Grande, NM ................................................................................................................. 7

Figure 3e. Colorado River at Lake Mead, AZ ................................................................................... 7

Figure 3f. Gila River, AZ ..................................................................................................................... 7

Figure 3g. Kern River, CA ................................................................................................................... 7

Figure 3h. Santa Ynez River, CA ........................................................................................................ 7

Figure 3i. Verde River, AZ ................................................................................................................. 11

Figure 3j. Rio Grande, NM ................................................................................................................ 11

Figure 3k. Lower Colorado River, AZ .............................................................................................. 11

Figure 3l. Lower San Pedro River, AZ ............................................................................................. 11

Figure 3m. Salt River, AZ.................................................................................................................. 11

Figure 3n. Colorado River, AZ ......................................................................................................... 11

Figure 3o. Lower San Pedro River, AZ ............................................................................................ 11

Figure 4. Generalized breeding chronology for the willow flycatcher in the Southwest. ................... 13

LIST OF TABLES

Table 1. Interpretation of willowflycatcher survey results (assuming no observer error). ................. 22

LIST OF FIGURES

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A Southwestern Willow Flycatcher Natural History Summary and Survey Protocol

The southwestern willow flycatcher (Empi-donax traillii extimus) is an endangered speciescurrently known to breed at only about 75 sites inriparian areas throughout the southwest. Theknown breeding population is estimated at between300 and 500 pairs. The flycatcher nests only in denseriparian vegetation associated with streams, rivers,lakes, springs, and other watercourses and wetlands.

E.t. extimus populations have declined duringthe twentieth-century, primarily because of habi-tat loss and modification (see Threats, page 15). In1991 the U.S. Fish and Wildlife Service (USFWS)designated the southwestern willow flycatcher as acandidate category 1 species (USFWS 1991). InJuly 1993, the USFWS proposed to list E.t. exti-mus as an endangered species and to designatecritical habitat (USFWS 1993). A final ruling list-ing E.t. extimus as endangered was published inFebruary 1995, although designation of criticalhabitat was postponed (USFWS 1995).

The southwestern willow flycatcher is also listedas an endangered species or species of concern inArizona (Arizona Game and Fish Department, inprep.), New Mexico (New Mexico Departmentof Game and Fish 1996), California (California De-partment of Fish and Game 1991), and Utah (UtahDivision of Wildlife Resources 1997).

Sound management and conservation of anendangered species requires current, detailed in-formation on the species’ abundance, distribution,and natural history. Unfortunately, there is rela-

tively little published information available on E.t.extimus. Most existing data is found in agency orconsulting firm reports, unpublished museumrecords, or researcher databases. Access to such in-formation is difficult, limiting the data’s value.

From a management and conservation perspec-tive, it is crucial that the maximum possible numberof southwestern willow flycatcher breeding areasbe identified and monitored. It is also imperativeto determine potential habitat areas where willowflycatchers do not currently occur. Effective, stan-dardized survey protocols and consistent reportingare crucial to conservation and management of en-dangered species, on both local and regional levels.However, the willow flycatcher is a difficult spe-cies to survey for and identify, and inconsistent orineffective surveys are of little value and wouldhinder regional and rangewide analyses.

We developed this document to provide up-to-date information about southwestern willowflycatcher biology and to furnish a standardized sur-vey protocol. The first section summarizes thecurrent state of knowledge regarding southwest-ern willow flycatcher natural history, based on awide array of published and unpublished litera-ture. Emphasis is given to information relevant toflycatcher conservation and management, and toconducting and interpreting surveys. The secondsection details a standard survey protocol that pro-vides for consistent data collection, reporting, andinterpretation.

BACKGROUND

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Breeding Range and TaxonomyFour subspecies of willow flycatcher are com-

monly recognized in North America (Hubbard1987, Unitt 1987). The subspecies occupy distinctbreeding ranges (Figure 1) and are differentiatedprimarily by subtle differences in color and mor-phology. The breeding range of the southwesternwillow flycatcher includes southern California(from the Santa Ynez River south), Arizona, NewMexico, southwestern Colorado, extreme south-ern portions of Nevada and Utah, and westernTexas (although recent breeding records from westTexas are lacking). Records of probable breedingsouthwestern willow flycatchers in Mexico are fewand restricted to extreme northern Baja Califor-nia del Norte and Sonora (Unitt 1987, Wilbur1987).

The southwestern willow flycatcher was de-scribed by A. R. Phillips (1948), from a collectionby G. Monson from the San Pedro River in south-

eastern Arizona. It is generally paler than otherwillow flycatcher subspecies, although this differ-ence is indistinguishable without considerableexperience and training, and study skins as com-parative reference material. The southwesternsubspecies differs in morphology (primarily wingformula) but not overall size. The taxonomic sta-tus of E.t. extimus was critically reviewed andconfirmed by Hubbard (1987), Unitt (1987), andBrowning (1993), and accepted by most authors(e.g., Aldrich 1951, Behle and Higgins 1959,Phillips et al. 1964, Oberholser 1974, Monson andPhillips 1981, Harris et al. 1988, Schlorff 1990,Harris 1991, USFWS 1991 and 1992).

Migration and Winter RangeWillow flycatchers (all subspecies) breed in

North America, but winter in Mexico, CentralAmerica, and possibly northern South America(Phillips 1948, Stiles and Skutch 1989, Peterson

Figure 1. Breeding ranges of the willow flycatcher subspecies. Adapted from Unitt 1987 and Browning 1993.

SECTION I: NATURAL HISTORY

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1990, Ridgely and Tudor 1994, Howell and Webb1995). Specific wintering sites for the southwest-ern race are currently unknown. Southwesternwillow flycatchers typically arrive on breedinggrounds between early May and early June(Muiznieks et al. 1994, Maynard 1995, Sferra etal. 1997). Because arrival dates vary annually andgeographically, northbound migrant willow fly-catchers (of all races) pass through areas where E.t.extimus have already begun nesting. Similarly,southbound migrants in late July and August mayoccur where southwestern willow flycatchers arestill breeding (Unitt 1987).

HabitatThe southwestern willow flycatcher breeds in

dense riparian habitats in all or part of seven south-western states, from sea level in California to over

2600 m in Arizona and southwestern Colorado.Although other willow flycatcher subspecies maybreed in shrubby habitats away from water, E.t.extimus breeds only in dense riparian vegetationnear surface water or saturated soil. Other charac-teristics such as dominant plant species, size andshape of habitat patch, canopy structure, vegeta-tion height, etc., vary widely among sites, asdescribed below.

Southwestern willow flycatcher breeding habi-tat can be broadly described and classified basedon plant species composition and habitat structure.These two habitat characteristics are the most con-spicuous to human perception, but are not the onlyimportant components. However, they have provenuseful in conceptualizing, selecting and evaluatingsuitable survey habitat, and in predicting wherebreeding flycatchers are likely to be found.

Narrative descriptions of four general habitattypes used throughout the southwestern willowflycatcher’s range are provided below. The photo-graphs in Figure 3 provide examples of some ofthe variation in southwestern willow flycatcherbreeding habitat. The habitat “types” describedbelow include a continuum of plant species com-position (from nearly monotypic to mixed species)and vegetation structure (from simple, single stra-tum patches to complex, multiple strata patches).The intent of the descriptions and photographs isto provide a general guide for evaluating suitablesurvey habitat.

Monotypic high-elevation willow: [Figures 3a-b]Nearly monotypic, dense stands of willow (oftenSalix exigua or S. geyeriana above 2300 m in Ari-zona), 3 - 7 m in height with no distinct overstorylayer; often associated with sedges, rushes, nettlesand other herbaceous wetland plants; usually verydense structure in lower 2 m; live foliage density ishigh from the ground to the canopy.

Monotypic exotic: [Figures 3c-d] Nearly mono-typic, dense stands of exotics such as saltcedar(Tamarix spp.) or Russian olive (Elaeagnus

Figure 2. Willow flycatcher breeding and winteringranges.

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Breeding

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angustifolia), 4 - 10 m in height forming a nearlycontinuous, closed canopy (with no distinct over-story layer); lower 2 m often very difficult topenetrate due to dense branches, however, livefoliage density may be relatively low, 1 - 2 m aboveground, but increases higher in the canopy; canopydensity uniformly high.

Native broadleaf dominated: [Figure 3e - h] Com-posed of single species (often Goodding’s [Salixgoodingii]or other willow species) or mixtures ofnative broadleaf trees and shrubs including (but notlimited to) cottonwood (Populus spp.), willows,boxelder (Acer negundo), ash (Fraxinus spp.), alder(Acnus spp.), and buttonbush (Cephalanthusoccidentalis), height from 3 - 15 m; characterizedby trees of different size classes; often (but not al-ways) a distinct overstory of cottonwood, willowor other broadleaf tree, with recognizablesubcanopy layers and a dense understory of mixedspecies; exotic/introduced species may be a rarecomponent, particularly in the understory.

Mixed native/exotic: [Figure 3i - l] Dense mix-tures of native broadleaf trees and shrubs (such asthose listed above) mixed with exotic/introducedspecies such as saltcedar or Russian olive; exoticsare often primarily in the understory, but may be acomponent of overstory; the native and exoticcomponents may be dispersed throughout the habi-tat or concentrated as a distinct patch within a largermatrix of habitat; overall, a particular site may bedominated primarily by natives or exotics, or be amore-or-less equal mixture.

Regardless of the plant species composition orheight, occupied sites always have dense vegeta-tion in the patch interior (Figures 3m - o). Thesedense patches are often interspersed with smallopenings, open water, or shorter/sparser vegeta-tion, creating a mosaic that is not uniformly dense.

Riparian patches used by breeding flycatchersvary in size and shape, and may be a relativelydense, linear, contiguous stand (Figure 3e) or an

irregularly-shaped mosaic of dense vegetation withopen areas (Figure 3a). Southwestern willow fly-catchers have nested in patches as small as 0.8 ha(e.g., Grand Canyon) and as large as several hun-dred hectares (e.g., Roosevelt Lake, AZ; LakeMead, AZ). However, flycatchers have not beenfound nesting in narrow, linear riparian habitatsthat are less than 10 m wide, although they willuse such linear habitats during migration.

Flycatcher territories and nests are typically nearopen water, cienegas, marshy seeps, or saturatedsoil, and flycatchers sometimes nest where the nestplants are in standing water (Sferra et al. 1997, M.Whitfield and R. McKernan unpublished data).However, in the Southwest, hydrological condi-tions at a site can vary remarkably within a seasonand between years. At some locations, particularlyduring drier years, water or saturated soil is onlypresent early in the breeding season (i.e., May andpart of June). At other sites, vegetation may beimmersed in standing water during a wet year, butbe hundreds of meters from surface water in dryyears. This is particularly true of reservoir sites suchas the Kern River at Lake Isabella (CA), TontoCreek and Salt River at Roosevelt Lake (AZ), andthe Rio Grande near Elephant Butte Reservoir(NM). There may be a total absence of water orvisibly saturated soil for several years at some breed-ing sites where the river channel has been recentlymodified (e.g., by creation of pilot channels),subsurface flows altered (e.g., from agriculturalrunoff), or the river channel has changed naturally(Sferra et al. 1997). However, we do not knowhow long such sites will continue to supportriparian vegetation and/or remain occupied bybreeding flycatchers.

Other potentially important aspects of south-western willow flycatcher habitat includedistribution and isolation of vegetation patches,hydrology, prey types and abundance, parasites,predators, environmental factors (e.g., temperature,humidity), and interspecific competition. Popula-tion attributes such as demography (i.e., birth anddeath rates, age-specific fecundity), distribution of

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Figure 3a. Little Colorado River (Apache Co.)2510 m - Monotypic Geyer willow habitat in-fluenced by beaver activity and surrounded bywet meadow and ponderosa pine forest. The nu-merous openings and standing water create amosaic that is not obvious from ground level(compare with 3b), exemplifying how aerialphotos help determine extent of habitat andsurvey routes. Note roadway in lower right forscale.

Figure 3b. Ground view of 3a. Notice willowsare low stature (height <4 m), very dense, butlacking any overstory. Standing water presentdue to beaver activity. Flycatchers often foragein the openings adjacent to nesting sites.

Legends for Photos

Figure 3c. Tonto Creek inflow to RooseveltLake (Gila Co.) 650 m - Nearly monotypic standof saltcedar 7 - 10 m tall, very dense through-out with high canopy cover, but no distinctoverstory. Drought conditions prevailed at thetime of this photograph. However, in previousyears saltcedar trees have been in several centi-meters of standing water in early June.

Figure 3d. Rio Grande at San Juan Pueblo (RioArriba Co.) 1720 m - This habitat adjacent tothe Rio Grande is comprised mostly of Rus-sian olive. The Russian olive is 7 - 10 m in heightand very dense. Several large cottonwoods arealso interspersed providing a hint of an over-story and exemplifying part of the continuumfrom monotypic to mixed stands.

Figure 3e. Lake Mead delta (Coconino Co.)365 m - This photo of the Colorado River in-flow to Lake Mead demonstrates the potentialfor large tracts of native riparian habitat to de-velop on managed river systems. This 450+ hastand is comprised mostly of Goodding’s wil-low with some coyote willow (S. exigua) andsaltcedar interspersed. The Goodding’s willowsaveraged 7 m in height. Willows were used byflycatchers even when nest tree bottoms wereinundated by up to 78 cm of water.

Figure 3f. Gila River (Pinal Co.) 515 m - Habitatcomprised mostly of Goodding’s willow withcottonwood interspersed. Characterized by treesof different age and size classes, downed or over-hanging trees creating dense tangles in lowerstrata, and a distinct overstory of cottonwoodand willow up to 12 m in height.

Figure 3g. South Fork Kern River (Kern Co.)775 m - This multilayered native riparian wood-land is comprised of cottonwood and two speciesof willow (S. laevigata, S. gooddingii) with a denseunderstory of stinging nettle (Baccharis salicifolia)and hoary nettle (Urtica dioica). Although notobvious in photo, water is present throughoutthe patch and is typically within 3 m of nesttrees.

Figure 3h. Santa Ynez River (Santa Barbara Co.)120 m - Another example of native riparianhabitat comprised of multiple species (cotton-wood, willow, boxelder), a dense understory, andmultiple vegetation strata adjacent to flowingwater. Understory species include arroyo wil-low (S. lasiolepis), coyote willow (B. salicifolia),and poison oak (Taxicodendron diversilobum) inaddition to young cottonwood and tree willow.

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Legends for Photos

Figure 3i. Verde River (Yavapai Co.) 1025 m -This small (1.5 ha) mixed native/exotic ripar-ian habitat is typical of many flycatcher nestingsites in Arizona. Cottonwood, boxelder, andGoodding’s willow dominate the canopy, whilesaltcedar is the predominant understory species.Dense understory and high foliage volume inall strata. In addition to the mainstem of theVerde River in foreground, a small spring keepsflowing water throughout the interior of thispatch.

Figure 3j. Rio Grande at San Marcial (SocorroCo.) 1360 m - An example of an extensive standof willow (Goodding’s and coyote), cottonwood,and saltcedar above Elephant Butte Reservoir.Dense stands of young trees and a uniformcanopy height (5 - 6 m) characterize some areas,while in others cottonwood and willow form anoverstory above dense saltcedar. In some yearsbases of flycatcher nest trees are inundated; indrought years water may be diverted far upstreamfrom this site.

Figure 3k. Lower Colorado River at LakeHavasu (Mohave Co.) 140 m - Along the lake’sshore this tall (12 m), multi-storied cottonwood-willow gallery forest has a dense understory ofsaltcedar and younger cottonwood and willowand is adjacent to a cattail marsh.

Figure 3l. Cook’s Lake along the San PedroRiver (Pinal Co.) 645 m - Note the density ofthe understory, which is comprised of button-bush, willow, saltcedar, and velvet ash (also see3l). A willow flycatcher nest is visible 2.5 cmright of and 0.5 cm below, the upper left cornerof photo.

Figure 3m. Salt River inflowto Roosevelt Lake (Gila Co.)650 m - Interior portion of fly-catcher habitat. Note thedensity just above ground levelof this monotypic saltcedarstand (also see 3c). Plant struc-ture contains little live foliage.

Figure 3n. Colorado River inGrand Canyon (Coconino Co.)855 m - Note the height anddensity of this decadent stand ofnearly monotypic salt-cedar.External edge shown includesmuch live foliage, but internalportion resembles 3m.

Figure 3o. Cook’s Lake alongSan Pedro River (Pinal Co.) 645m - This photo shows the multi-storied structure of thisbuttonbush swamp. Dense but-tonbush is primary understorycomponent (with some saltce-dar interspersed) whileGoodding’s willow and velvetash form a distinct canopy andoverstory.

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breeding groups across the landscape, flycatcher dis-persal patterns, migration routes, site fidelity,philopatry, and conspecific sociality also influencewhere flycatchers are found and what habitats theyuse. Most of these factors need further study, butmay be critical to understanding current popula-tion dynamics and habitat use. Refer to Wiens(1989 and 1996) for additional discussion of habi-tat selection and influences on bird species andcommunities.

The ultimate measure of habitat suitability isnot simply whether or not a site is occupied. Suit-able habitats are those in which flycatcherreproductive success and survivorship results in astable or growing population. Without long-termdata showing which sites have stable or growingpopulations, we cannot determine which habitatsare suitable or optimal for breeding southwesternwillow flycatchers. Some occupied habitats maybe acting as population sources, while others maybe functioning as population sinks (Pulliam 1988).

Migrant willow flycatchers may occur in non-riparian habitats and/or be found in riparianhabitats unsuitable for breeding. Such migration

stopover areas, even though not used for breeding,may be critically important resources affecting lo-cal and regional flycatcher productivity and survival.

Breeding Chronology and BiologyFigure 4 presents a generalized breeding chro-

nology for willow flycatchers in the southwest.Unless otherwise noted, the information that fol-lows and upon which Figure 4 is based, comesfrom Unitt 1987, Brown 1988, Whitfield 1990,Skaggs 1995, Sogge 1995a and 1995b, Maynard1995, Petterson and Sogge 1996, Sferra et al. 1997,and Sogge et al.(in press). Extreme or record datesfor any stage of the breeding cycle may vary asmuch as a week from the dates presented.

Males generally arrive at breeding areas first,with females typically arriving a week or two later.Males are usually monogamous, but polygynyrates of 10-20% annually have been recorded atthe Kern River Preserve in California (Whitfield,pers. comm.). Nest building usually begins withina week of pair formation. Egg laying begins (rarely)as early as late May, but more often starts in earlyto mid-June. Chicks can be present in nests from

Figure 4. Generalized breeding chronology for the willow flycatcher in the Southwest.Extreme or record dates may occur slightly earlier or later than indicated.

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mid-June through early August. Young typicallyfledge from nests from late June through mid-August; later fledglings are often products ofrenesting attempts. Adults depart from breedingterritories as early as mid-August, but may stay untilmid-September if they fledged young late in theseason (M. Whitfield and W. Haas, unpublisheddata). Males that fail to attract or retain mates, andmales or pairs that are subject to significant distur-bance (such as repeated nest parasitism, predation,etc.) may leave territories earlier (mid-July). Fledg-lings probably leave the breeding areas a week ortwo after adults, but few details are known.

Southwestern willow flycatcher territory sizevaries, probably due to differences in populationdensity, habitat quality, and nesting stage. Early inthe season, territorial flycatchers may move sev-eral hundred meters between singing locations,although this has been noted only at sites with oneor two territorial males (Sogge et al. 1995, Pettersonand Sogge 1996, R. Marshall pers. obs.). It is notknown if such movements represent defense of theentire area encompassed by singing locations. Dur-ing incubation and nestling phases territory size,or at least the activity centers of pairs, can be verysmall. Estimated territory sizes are 0.24 - 1.3 hafor monogamous males and 1.1 - 2.3 ha for po-lygynous males at the Kern River (Whitfield andEnos 1996), 0.06 - 0.2 ha for birds in 0.6 - 0.9 hapatches on the Colorado River (Sogge et al. 1995)and 0.2 - 0.5 ha in a 1.5 ha patch on the VerdeRiver (Sogge 1995b). Flycatchers may increase theiractivity area after young are fledged, and use non-riparian habitats adjacent the breeding area.

Nests and EggsSouthwestern willow flycatchers build open

cup nests approximately 8 cm high and 8 cm wide(outside dimensions), exclusive of any danglingmaterial at the bottom. Nests are typically placedin the fork of a branch with the nest cup supportedby several small-diameter vertical stems. The mainforked branch may be oriented vertically, horizon-tally, or at an angle, and stem diameter for the main

supporting branch can be as small as 3 - 4 cm.Vertical stems supporting the nest cup are typically1 - 2 cm in diameter.

Nest height varies considerably, and may becorrelated with height of nest plant, overall canopyheight, and height of the vegetation strata that con-tains small twigs and live growth. Southwesternwillow flycatcher nests have been found from 0.6- 18 m above the ground. Flycatchers using mainlynative broadleaf riparian habitats often nest rela-tively low (usually 2 - 3 m above ground), whereasthose using mixed native/exotic and monotypicexotic riparian habitats often nest higher (usually4 - 7 m above ground). However, in any habitattype, nests may be placed at any height where ap-propriate twig structure and plant cover occurs.

Historically, 75 - 80 % of southwestern willowflycatcher nests were placed in willows (HerbertBrown field notes 1902, Phillips 1948, Phillips etal. 1964, Hubbard 1987, Unitt 1987, San DiegoNatural History Museum 1995). Currently, the fly-catcher nests in a variety of plant species. At themonotypic willow stands that characterize highelevation sites in Arizona, Geyer willow was usedalmost exclusively for nesting (Sferra et al. 1997).At the inflow to Lake Mead on the Colorado River,Goodding’s willow was the primary nesting sub-strate (R. McKernan unpublished data). Along theGila River in Grant County, New Mexico, 76%of flycatcher nests were placed in boxelder (thedominant understory species), with the remainderin other native and exotic plants (Skaggs 1995).At the inflows of Tonto Creek and Salt River toRoosevelt Lake in Gila County, Arizona, both ofwhich include nearly monotypic stands of saltcedar,all flycatcher nests were placed in saltcedar (Sferraet al. 1997). On the San Luis Rey River in SanDiego County, California, approximately 90% offlycatcher nests were in live oak (Quercus agrifolia),which became the dominant plant species adja-cent the river following willow removal in the1950s (W. Haas, pers. comm.). Southwestern wil-low flycatcher nests have also been found inbuttonbush, black twinberry (Lonicera involucrata),

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Fremont cottonwood, alder (Alnus spp.), blackberry(Rubus ursinus), baccharis (baccharis spp.) and sting-ing nettle (Urtica spp.).

Willow flycatcher eggs are buffy or light tan,approximately 18 mm long and 14 mm wide, withbrown markings in a wreath at the blunt end.Clutch size is usually 3 or 4 eggs for first nests.Incubation lasts 12 - 13 days from the date the lastegg is laid, and all eggs typically hatch within 24 -48 hrs of each other.

The female provides most or all initial care ofthe young, though the role of the male increaseswith the age and size of nestlings. Young willowflycatchers fledge at 12 - 15 days of age, and stayclose to the nest and each other for 3 - 5 days.Recently fledged birds may repeatedly return toand leave the nest during this period (Spencer etal. 1996). Fledglings stay in the natal area a mini-mum of 14 - 15 days after fledging, possibly muchlonger. Male and female adults both feed thefledged young, which beg loudly (typically a “peep”call).

Second clutches within a single breeding sea-son are uncommon if the first nest is successful,though this may vary between sites and years.Willow flycatchers often attempt another nest ifthe first nest is unsuccessful. Replacement nestsare built in the same territory, either in the samenest plant or at a distance of up to 20 m from theprevious nest. In one case, renesting flycatchersreused the same nest (W. Haas, pers. comm.).Replacement nest building and egg laying canoccur (uncommonly) as late as late-July or earlyAugust. Pairs may attempt a third nest if thesecond fails (Sferra et al. 1997, Whitfield pers.comm.). Clutch size (and therefore potential pro-ductivity) decreases with each nest attempt(Whitfield and Strong 1995).

Site Fidelity and PersistenceMost existing information on southwestern

willow flycatcher site fidelity comes from studiesby Whitfield (1990), Whitfield and Strong (1995),and Whitfield and Enos (1996) at the Kern River

Preserve (CA). Twenty-one of 58 nestlings (36%)banded since 1993 returned to the study site tobreed. Since 1989, 18 of 67 birds (31%) banded asadults returned to breed at the study site for atleast one year. Six of the 67 (9%) returned to breedfor two years. Nestling return rates, which are afunction of overwinter survival and site fidelity,varied with fledging date. Among banded juvenileflycatchers that were recaptured in subsequent years,Whitfield and Strong (1995) found significantlyhigher return rates in juveniles fledged on orbefore July 20th compared with those fledgedafter July 20th (22% vs 6%, respectively).

Little is known about southwestern willow fly-catcher movement between breeding sites, or aboutthe persistence of breeding sites. “Large” popula-tions such as the Kern River Preserve (CA), SanPedro River (AZ), and Gila River (NM) have per-sisted for 10 or more years. On the other hand,small populations may be ephemeral and last onlya few years. Between 1992 and 1995, a small popu-lation on the Verde River in Arizona decreased fromfour pair to two pairs (Sogge 1995b), and wasabsent in 1996 (Sferra et al. 1997). Breeding popu-lations may also reappear at unoccupied sitesfollowing 1-5 yr absences (Sogge and Tibbitts1994, Sogge et al. in press). Therefore, one cannotassume a habitat is unsuitable or unoccupied inthe long term based on flycatchers absence duringonly a single year, especially if there is evidence ofrecent occupancy.

Threats to the Flycatcher and HabitatThe most significant historical factor in the de-

cline of the southwestern willow flycatcher is theextensive loss, fragmentation, and modification of ri-parian breeding habitat. Large scale losses of south-western wetlands have occurred, particularly thecottonwood-willow riparian habitats of thesouthwestern willow flycatcher (Phillips et al. 1964,Johnson and Haight 1984, Katibah 1984, Johnsonet al. 1987, Unitt 1987, General Accounting Office1988, Dahl 1990, State of Arizona 1990). Changesin the riparian plant community havr reduced,

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degraded and eliminated nesting habitat for the wil-low flycatcher, curtailing its distribution and numbers(Serena 1982, Cannon and Knopf 1984, Taylor andLittlefield 1986, Unitt 1987, Schlorff 1990). Habitatlosses and changes have occurred (and continue tooccur) because of urban, recreational, and agricul-tural development, water diversion and impound-ment, channelization, livestock grazing, and replace-ment of native habitats by introduced plant species(see USFWS 1993 and Tibbitts et al. 1994 for de-tailed discussions of threats and impacts). Hy-drological changes, natural or man-made, can greatlyreduce the quality and extent of flycatcher habitat.Although riparian areas are often not considered asfire-prone, several sites with relatively large num-bers of breeding willow flycatchers wererecentlydestroyed by fire (Paxton et al. 1996), and manyothers are at risk to similar catastrophic loss. Firedanger in these riparian systems may be exacerbatedby conversion from native to exotic vegetation (suchas salt cedar), diversions or reductions of surfacewater, and drawdown of local water tables.

Brood parasitism by the brown-headed cow-bird is another significant and widespread threatto the southwestern willow flycatcher(Rowley1930, Garret and Dunn 1981, Brown1988, Whitfield 1990, Harris 1991, Sogge 1995aand 1995b, USFWS 1993 and 1995, Whitfieldand Strong 1995, Sferra et al. 1997). Althoughsome host species seem capable of simultaneouslyraising both cowbirds and their own chicks, suchis not the case with southwestern willow fly-catchers. Of the hundreds of flycatcher nestsmonitored throughout the Southwest between1988 and 1996, only two are known to havesuccessfully fledged both flycatchers and cow-birds. In all other cases, parasitism causes completenest failure or the successful rearing of onlycowbird chicks (Brown 1988, Whitfield 1990,Whitfield and Strong 1995, Sogge 1995a and1995b, Maynard 1995, Sferra et al. 1997, Soggeet al. in press). Therefore, once a southwesternwillow flycatcher nest is parasitized, it has almostno chance of producing flycatcher young.

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The primary objectives of this protocol are toprovide a standardized survey technique to detectsouthwestern willow flycatchers and determinebreeding status, and provide consistent and stan-dardized data reporting. The survey technique will,at a minimum, help determine presence or absenceof the species in the surveyed habitat for that breed-ing season.

This protocol is designed for use by personswho are non-specialists with Empidonax flycatchersor who are not expert birders. However, surveyorsmust have sufficient knowledge, training, andexperience with bird identification and surveys todistinguish the willow flycatcher from other non-Empidonax species, and recognize the willowflycatcher’s primary song. Surveys conductedimproperly or by unqualified or inexperienced per-sonnel may lead to unwarranted and inaccurateresults.

Surveys conducted by qualified personnel in aconsistent and standardized manner will enablecontinued monitoring of general population trendsat and between sites. Annual or periodic surveys incooperation with state and federal agencies shouldaid resource managers in fulfilling their basicinformation needs for the southwestern willowflycatcher.

The first version of this protocol (Tibbitts etal. 1994) has been used extensively and success-fully for three years. Hundreds of flycatcher surveysconducted throughout the Southwest since 1994have taught us much about the usefulness andapplication of this survey technique. Two impor-tant lessons are: (1) the tape-playback techniqueworks and detects flycatchers that would have beenoverlooked; and (2) with appropriate effort,general biologists without extensive experiencewith Empidonax can find and verify willow fly-catcher breeding sites.

This revised protocol is still based on tape-playback techniques and detection of singingindividuals. However, it includes changes in the

A number of factors conspire to make south-western willow flycatcher surveys relatively difficultand anything but straightforward. The willow fly-catcher is one of ten Empidonax flycatchers commonin North America, all of which look very muchalike. Like all Empidonax, willow flycatchers arenondescript in appearance, making them difficult tosee in dense breeding habitat. Although the willowflycatcher has a characteristic fitz-bew song whichdistinguishes it from other birds (including otherEmpidonax), willow flycatchers are not vocal at alltimes of the day or during all parts of the breedingseason. Because southwestern willow flycatchers arerare and require relatively dense riparian habitat,they may occur only in a small area within a largerriparian system, thus decreasing detectability dur-ing general bird surveys. Migrating willowflycatchers (of all subspecies) often sing during theirmigration through the Southwest, and could there-fore be confused with local breeders. In addition,southwestern willow flycatchers are in breedingareas for only 3-4 months of the year. Surveys con-ducted too early or late in the year would fail tofind flycatchers even at sites where they breed.

These life history characteristics and demographicfactors influence how southwestern willow fly-catcher surveys should be conducted. This protocolis based on the use of repeated tape-playbacksurveys during pre-determined periods of thebreeding season, to confirm presence or absenceat a site. Such species-specific survey techniquesare necessary to collect reliable presence/absenceinforma- tion for rare species (Verner 1985, Bibbyet al. 1992, Reed 1996).

Currently, federal endangered species per-mits are required for surveys in all USFWSregions where the southwestern willow fly-catcher breeds. State permits may also be requiredbefore you can survey within any of the statesthroughout the southwestern willow flycatcher’srange: be certain to check with the appropriatestate wildlife agency in your area.

SECTION 2: THE SURVEY PROTOCOL

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timing and number of surveys to increase the prob-ability of detecting flycatchers and to helpdetermine if they are breeders or migrants. Changesin the survey data sheets make them easier to useand submit, and allow reporting all site visits withina single year on one form.

This protocol does not address issues and tech-niques associated with nest monitoring or other fly-catcher research activities. Those efforts are beyondthe scope usually needed, and require advancedlevels of experience and skills to gather useful dataand avoid potential negative effects to the flycatcher.

Biologists who are not expert birders or spe-cialists with regard to Empidonax flycatchers caneffectively use this protocol. However, users mustattend the mandatory southwestern willow fly-catcher survey training workshop, and haveknowledge and experience with bird identifica-tion and ecology sufficient to effectively apply thisprotocol. See Contacts section (page 29)for a list-ing of agencies offering survey training workshop.

PermitsCurrently, all USFWS regions within the

southwestern willow flycatcher breeding rangerequire that all persons conducting surveys perthis protocol obtain endangered species permits. Itmay take several months to receive permits, soapply early to avoid delays in starting your surveys.State permits may also be required. Check withthe appropriate state wildlife agency. You must alsoobtain permission from government agencies andprivate landowners prior to conducting any surveyson their lands.

Pre-survey PreparationSurveyors should study drawings and photo-

graphs of willow flycatchers, and where possible,examine study skins or mounts. It is critical forsurveyors to be familiar with willow flycatcher vo-calizations before going in the field. Although thefitz-bew song is the basis of verifying detectionsusing this protocol, willow flycatchers use manyother vocalizations that are valuable in locating birds

and breeding sites. We strongly encourage that allsurveyors learn as many vocalizations as possible(see Stein 1963). If possible, study recordings ofsouthwestern subspecies; tapes are available throughthe contacts listed at the end of this protocol.Several commercial bird song tapes include willowflycatcher vocalizations, but these tapes typicallyinclude only a few vocalizations and the dialectsmay differ from those in the southwest.

If possible, visit known willow flycatcher breed-ing sites (but only after obtaining landowner ormanagement agency permission) to become famil-iar with flycatcher appearance, behavior,vocalizations, and habitat. Such visits are usuallypart of the standardized flycatcher survey work-shops. All visits should be coordinated withUSFWS, State wildlife agencies, and the propertymanager/owner, and must avoid disturbance toresident flycatchers.

Surveyors must be able to identify, by sight andvocalizations, other species likely to be found insurvey areas which may be confused with south-western willow flycatchers. These include Bell’s vireo(Vireo bellii), western wood-pewee (Contopussordidulus), young or female vermillion flycatchers(Pyrocephalus rubinus), and other Empidonax fly-catchers. At a distance, partial song or call notes ofBell’s vireo, ash-throated flycatchers (Myiarchuscinerascens) and some swallows can sound consider-ably like a fitz-bew. Surveyors should also be ableto identify (by sight and sound) brown-headedcowbirds. It is worthwhile to make one or morepre-survey trips to the survey sites (or other similarareas) to become familiar with the local bird fauna.

Be prepared to work hard and remain focusedand diligent in a wide range of physically demand-ing conditions. At many sites these include heat,cold, wading or swimming through flowing or stag-nant water, muddy or swampy conditions, crawlingthrough dense thickets (often on hands and knees),and exposure to snakes, skunks, and biting insects.Familiarity with the survey site prior to the firstsurveys is the best way to be prepared for the con-ditions you will experience.

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EquipmentThe following equipment is necessary to con-

duct the surveys:(1) USGS topographic maps of the area (a

marked copy to be attached to survey datasheet). Be sure to ALWAYS submit a copy of atopo map with survey area and flycatchersightings clearly marked.

(2) Standardized survey form (bring more cop-ies than you think you need).

(3) Lightweight tape player (with adequate vol-ume to carry well; use portable speakers ifnecessary).

(4) Extra tape player and batteries (dirt, wa-ter, dust and heat often cause equipment failure,and having backup equipment helps avoidaborting a survey due to equipment loss).

(5) Willow flycatcher tapes; two or more tapes persurveyor (tapes DO get damaged and wear outin the field, extra tapes are very important).One tape per surveyor can be obtained throughthe contacts listed in the back of this protocol(you will have to make your own copies).

(6) Clipboard and permanent (waterproof)ink pen (we recommend recording survey re-sults directly on the survey data form, to assurethat you collect and record all required data).

(7) Aerial photograph (if available). Aerial pho-tographs can significantly improve your surveysby allowing you to accurately target your ef-forts, thus saving time (and energy) in the field.Check with local planning offices and/or state/federal land management agencies for availabil-ity. Take color xerox copies, not the originalaerials, with you in the field. Aerials are alsovery useful when submitting your survey re-sults, but cannot be submitted in place of atopographic map.

(8) Binoculars and bird field guide.

The following equipment is recommended:(1) Camera and film (for habitat photos—

especially at sites where flycatchers are found).

(2) GPS unit—for determining survey coordi-nates and verifying location of survey plots ontopo maps.

(3) Survey flagging (conservative earth-tonecolors)—for marking survey sites and/orareas where flycatcher are detected. Check withthe local land owner or management agencybefore flagging sites.All survey results (both negative and positive)

should be recorded directly on data forms whenpossible. These data forms have been designed toprompt surveyors to record key information crucialto interpretation of survey results and character-ization of study sites. Even if no flycatchers are de-tected or habitat appears unsuitable, this is valuableinformation and should be recorded. Standardizeddata forms are provided in Appendix 1.

Willow flycatcher surveys are targeted at thisspecies and require a great deal of focused efforts.Surveyors must be constantly alert and concen-trate on detecting flycatcher responses. Therefore,field work such as generalized bird surveys (e.g.,point counts or walking transects) or other dis-tracting tasks should not be conducted duringwillow flycatcher surveys. Avoid bringing pets oradditional people who are not needed for the survey.Dress in muted earth-tone colors, and avoid wearingbright clothing.

Willow Flycatcher Identification :Physical Description

The southwestern willow flycatcher is asmall bird, approximately 15 cm long and weigh-ing about 11-12 g. Sexes look alike, and cannotbe distinguished by plumage. The upper partsare brownish-olive; a white throat contrasts withthe pale olive breast, and the belly is pale yellow.Two white wing bars are visible (juveniles havebuffy wing bars), and the eye ring is faint orabsent. The upper mandible is dark, and thelower mandible light. The tail is not strongly forked.When perched, the willow flycatcher often flicksits tail upward. The Empidonax flycatchers are a dif-ficult groups of birds to distinguish by appearance.

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For the purpose of this protocol, identificationof willow flycatchers cannot be made by sightalone; vocalizations are a critical identificationcriterion.

Vocalizations

Given that willow flycatchers look a lot likeother Empidonax flycatchers that may be present atsurvey sites, the most certain way to verify willowflycatchers in the field is by their vocalization.Willow flycatchers have a variety of vocalizations(see Stein 1963, McCabe 1991), but two are mostcommonly heard during surveys or in response totape-playback:

(1) Fitz-bew. This is the willow flycatcher’scharacteristic primary song (note that it is notunique to the southwestern subspecies). Male wil-low flycatchers may sing almost continuously forhours, with song rates as high as one song everyfew seconds. Song volume, pitch, and frequencymay change as the season progresses. During pro-longed singing bouts, fitz-bews are often separatedby short britt notes. Fitz-bews are most often givenby a male, but studies have shown female willowflycatchers also sing, sometimes quite loudly andpersistently (though generally less than males). Fly-catchers often sing from the top of vegetation, butwill also vocalize while perched or moving aboutin dense vegetation.

(2) Whitt. This is a call often used by birds ontheir territory, and is commonly heard even dur-ing periods when the flycatchers are not singing(fitz-bewing). The whitt call appears to be a contactcall between sexes, as well as an alarm call, par-ticularly when responding to disturbance near thenest. Whitt calls can be extremely useful for locat-ing willow flycatchers later in the season (whenfitz-bewing may be infrequent), but are easily over-looked by inexperienced surveyors. Whenflycatcher pairs have active nests (particularly onceyoung have hatched), whitts may be the mostnoticeable vocalization. However, many species ofbirds whitt, and a whitt is not a diagnostic charac-teristic for willow flycatchers.

The fitz-bew and whitt calls are the primary vo-calizations used to locate willow flycatchers.However, other less common willow flycatchervocalizations can be very useful in alerting survey-ors to the presence of flycatchers. These includetwittering vocalizations (typically given during in-teractions between flycatchers and sometimesbetween flycatchers and other birds), bill snapping,and wheeo’s. Because these sounds can be valuablein locating territories, they should be studied priorto going in the field. Willow flycatcher vocaliza-tion tapes are available from the agency contactslisted at the end of this protocol. Refer to Stein(1963) for detailed discussions of flycatcher vocal-izations.

Willow flycatcher song rates are highest earlyin the breeding season (late May - early June), andappear to decline after eggs hatch (Flett and Sand-ers 1987, Sogge and Tibbitts 1992). However, inareas with many territorial flycatchers or where anunpaired flycatcher is still trying to attract a mate,singing rates may be high well into July (Craig etal. 1992, Sogge 1995b). Isolated pairs can be muchquieter and harder to detect than pairs with adja-cent territorial flycatchers (M. Whitfield, pers.comm.). At some sites, pre-dawn singing (0330 -0500 hrs) appears to continue strongly at leastthrough mid-July (Sogge et al. 1995, Petterson andSogge 1996). Singing rates may increase again laterin the season, possibly coinciding with renestingattempts.

There are some periods during which willowflycatchers do not sing and even the use oftape-playback sometimes fails to elicit any response.This can be particularly true late in the breedingseason (Sogge et al. 1993, Muiznieks et al. 1994).Early and repeated surveys are the best way tomaximize the odds of detecting a singing flycatcherand determining its breeding status.

Special ConsiderationsTo avoid adverse impacts to willow flycatch-

ers, follow these guidelines when performing allsurveys:

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(1) Obtain all necessary federal, state, andagency permits prior to conducting any surveys.Failure to do so leaves you liable for violation ofthe Endangered Species Act and state laws.

(2) Do not play the tape more than necessaryand/or needlessly elicit vocal responses once wil-low flycatchers have been located and verified. Thismay distract resident birds from caring for eggs oryoung, or defending their territory. Excessive tapeplaying may also attract the attention of predatorsor brood parasites. Stop playing the survey tape assoon as you have confirmed the presence of a wil-low flycatcher at that locale, and do not play thetape again until you have moved to the next sur-vey location.

(3) Proceed cautiously while moving throughwillow flycatcher habitat. Continuously check thearea around you to avoid disturbance to nests ofwillow flycatchers and other species. Do not breakunderstory vegetation, even dead branches, to cre-ate a path through the surveyed habitat.

(4) Do not approach known or suspected nests.Nest searches and monitoring require specific stateand federal permits, and are not intended to be apart of this survey protocol.

(5) If you find yourself close to a nest (or asuspected nest), move away slowly to avoid star-tling birds. Avoid physical contact with the nest ornest tree, to prevent physical disturbance and leav-ing a scent. Do not leave the nest area by the sameroute that you approached. This leaves a “dead end”trail which could guide a potential predator to thenest/nest tree.

(6) Watch for and note the presence of poten-tial predators and nest parasites, particularly ravens,crows, jays, magpies, and cowbirds. If such preda-tors are in the immediate vicinity, wait for them toleave before playing the tape.

(7) If you use flagging to mark an area whereflycatchers are found, use earth-tone colors andmake certain the flagging is not near an active nest.Check with the property owner or land manage-ment agency before flagging to be sure that similarflagging is not being used for other purposes in

the area. Unless conducting specific (and autho-rized/permitted) nest monitoring, flagging shouldbe placed no closer than 30 m to any nest. Keepflagging inconspicuous from general public viewto avoid attracting people or animals to an occu-pied site, and remove it at the end of the breedingseason.

Timing and Number of VisitsPerforming repeated surveys during the early

to mid-nesting season maximizes the likelihood ofdetecting flycatchers and determining their breed-ing status. Single surveys, or surveys conducted tooearly or late in the breeding cycle, do not providedefinitive data and are of little value. This surveyprotocol requires a minimum of three surveys ateach site, one during each period outlined below,to document absence of willow flycatchers. Also,successive surveys must be at least 5 days apart;surveys conducted more closely are not consid-ered to be in separate survey periods.

Survey 1: 15 - 31 May

The timing of this survey is intended to coin-cide with the period of high singing rates in newlyarrived males, which tends to begin in early tomid-May. This is one of the most reliable times todetect flycatchers that have established their terri-tories. However, not all territorial males may havearrived by this time, and migrants (of all subspecies)may still be present and singing during this period.

Survey 2: 1 - 21 June

During this period, the earliest arriving malesmay already be paired and singing less, but laterarriving males should still be singing strongly. Thissurvey can provide insight about the status of fly-catchers detected during survey 1 (e.g., if detectedduring survey 1 but not survey 2, the first detec-tion may have been a migrant). Conversely,detecting a flycatcher at the same site on surveys 1and 2 increases the likelihood that the bird is not amigrant (but does not necessarily confirm it). Sur-vey period 2 is also the earliest time during which

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you are likely to find nesting activity by residentbirds.

Survey 3: 22 June - 10 July

Southwestern willow flycatchers should havearrived on their territories by this time. Flycatchersinging rates may have lessened, and most pairedflycatchers will have initiated nesting activity.Migrant willow flycatchers should no longer bepassing through the southwest; therefore, any fly-catchers that you detect are probably residentbreeders or nonbreeding floaters. Surveyors shoulddetermine if flycatchers detected during surveys 1and/or 2 are still present, and watch closely fornesting activity.

Southwestern willow flycatchers may notarrive and/or initiate breeding activities at higher

elevation sites (above 2000 m) until early June,possibly later in some years due to weather ormigration patterns. Therefore, flycatcher breedingchronology may be “set back” one or two weeksat such sites and surveys should be conducted inthe latter part of each period.

It may not require three trips to verify flycatcherpresence and/or breeding status. If, for example,willow flycatchers are found during surveys 1 or2 and are observed carrying nest material, this isconclusive verification of breeders as opposed tomigrants. However, three trips is the minimumnecessary to determine with relative confi-dence that willow flycatchers are probably notbreeding at a site in that year. Table 1 providesgeneral guidance for interpretation of surveyresults.

Table 1. Interpretations of willow flycatcher survey results (assuming no observer error).

#1 #3#2

N

Breeding activity observed1Interpretation

none B - Flycatchers present, but probablemigrants

Survey results

Flycatchers detectedduring survey? Yes/No

N N not applicable A - Flycatchers not present at site

N or Y N or Y N

N or Y N or Y Y none C - Flycatchers territorial, potential2breeders

N or Y N or Y Y presence of another ”unchallenged“ willowflycatcher in the immediate vicinity (indi-cates possible pair); whitt or interactioncalls between nearby flycatchers;countersinging or physical aggressionagainst another flycatcher; physical aggres-sion against cowbirds

D - Flycatchers territorial, probablebreeders

1Important note: Evidence of flycatcher breeding activity may be seen during any survey. This immediately signifiespossible, probable, or definite breeding status, depending on the nature of the observation. Conclusive signs ofbreeding activity (as listed in E above) during survey periods 1 or 2 verifies actual (or attempted) breeding at the site,even if no flycatchers are detected during period 3.2If a flycatcher is detected in the third survey period but no breeding activities are seen, the flycatcher should beconsidered a potential breeder. Potential breeders include unmated territorial birds, or mated pairs for whichbreeding activity simply was not observed.

N or Y N or Y Y willow flycatchers copulating; flycatchercarrying nest material, food or fecal sac; anactive nest; adult flycatchers feedingfledged young

E - Flycatchers territorial, definitebreeders

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We strongly encourage additional follow-upvisits to sites where resident flycatchers are veri-fied or suspected. Extra visits provide greaterconfidence about presence or absence of flycatch-ers at a site, as well as help in estimating the numberof breeding territories or pairs, and determiningbreeding status and the outcome of breeding ef-forts. However, avoid returning to a site so oftenas to damage the habitat, establish or enlarge trails,or cause undue disturbance to the flycatchers.

Survey MethodsThe survey methods described below fulfill the

primary objectives of documenting the presenceor absence of willow flycatchers, and determiningtheir status (territorial vs migrant). This protocol isprimarily a tape-playback technique, a provenmethod for eliciting response from nearby resi-dent willow flycatchers (Seutin 1987, Craig et al.1992, Sogge and Tibbitts 1994, Sferra et al. 1995).At each site, surveyors should broadcast recordedwillow flycatcher songs, and look and listen forresponses. In addition to maximizing the likeli-hood of detecting nearby flycatchers, this methodalso allows for positive identification by compari-son to the “known” willow flycatcher tape.

Documenting Presence / AbsenceBegin surveys as soon as there is enough light

to safely walk (about one hour before sunrise) andend by about 0900 - 1000 hrs, depending on thetemperature, wind, background noise, and otherenvironmental factors. If observers are camped inor near potential willow flycatcher habitat, after-noons and evenings can be spent in reconnaissanceof the site(s) and planning a survey strategy for thefollowing morning. If camped immediately adja-cent to survey sites, surveyors can awaken earlyand listen for flycatchers singing during the pre-dawn period (0330 - 0500 hrs), when territorialmales often sing loudly.

Conduct surveys from within the sites if it ispossible to do so without breaking vegetation ordamaging the habitat. Flycatchers often respond

most strongly if the tape is played from within thehabitat and territory, rather than from the periph-ery. In addition, it can be surprisingly difficult tohear singing willow flycatchers that are even a shortdistance away amidst the noise generated by manyother singing and calling birds. Therefore, it is pref-erable to survey from within the habitat, but alwaysmove carefully to avoid disturbing habitat or nests.Surveying can be done from the periphery whereterrain, extremely dense vegetation, or deep waterprohibit walking through the habitat.

Because flycatchers may be clustered withinonly a portion of a habitat patch, it is critical tosurvey all suitable habitat within the patch. Smalllinear sites may be thoroughly covered by a singletransect through the patch. For larger sites, choosea systematic survey path that assures complete patchcoverage throughout the length and breadth of thesite. This may require multiple transects, serpen-tine, zig-zag or criss-cross routes. Aerialphotographs are valuable tools to help plan andconduct surveys, and to assure complete coverage.Always move carefully through the habitat to avoiddisturbing vegetation or nests.

Initially approach each site and stand quietlyfor 1 - 2 minutes or longer, listening for spon-taneously singing flycatchers. A period of quietlistening is important because it helps acclimatesurveyors to background noises (which can be quiteloud due to roads, aircraft, machinery, waterways).It also allows surveyors to recognize and “filter out”the songs and calls of other bird species, lettingthem focus attention on listening for flycatchers.Although it happens rarely, some singing willowflycatchers will actually stop vocalizing andapproach quietly in response to a broadcast song.Therefore, playing a tape before listening for sing-ing individuals has at least some potential ofreducing detectability.

If you do not hear singing flycatchers duringthe initial listening period, broadcast the willow fly-catcher song tape for 15 - 30 seconds, then listenfor approximately 1- 2 minutes for a response.Repeat this procedure (including a 10 - 20 second

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quiet pre-broadcast listening period) every 20 - 30m throughout each survey site, more often if back-ground noise is loud. The tape should be played atabout the volume of natural bird calls, and not soloud as to cause distortion of the broadcast. Werecommend tapes include a series of fitz-bewsinterspersed with several whitts.

Response to the broadcast call could take sev-eral forms. Early in the breeding season(approximately May - mid-June), a responding wil-low flycatcher will usually move toward theobserver and sing (fitz-bew) from within or at thetop of vegetation. Actively territorial willow fly-catchers almost always vocalize strongly when atape 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 tapeor the first responding individual. Flycatchers canoften hear the tape from far away but will not usu-ally move outside of their territory, so listen fordistant responses. Another common response isalarm calls (whitts) or interaction twitters fromwithin nearby vegetation, particularly once nest-ing has begun. Willow flycatchers will often singafter a period of whitting in response to a tape, sosurveyors should remain in the area and quietlylisten for fitz-bews for several minutes. Because someflycatchers may initially respond by approachingquietly, particularly during periods 2 and 3, it iscritical to watch carefully for responding birds.

For the purpose of this protocol, detection ofa fitz-bew song is essential to identify a bird as awillow flycatcher. Similar appearing species (in-cluding other Empidonax flycatchers) occur asmigrants, and even breeders, at potential willowflycatcher sites. A few of these other species mayeven approach a broadcast willow flycatcher songand respond with vocalizations. In order to stan-dardize interpretation of survey results and assurea high degree of confidence in surveys conductedby biologists of varying experience and skill, posi-tive identification must be based on detection ofthe willow flycatcher’s most unique characteristic—its song. It is important to remember that the

whitt call is not unique to willow flycatchers, andtherefore cannot serve as the basis of a positive iden-tification. However, whitts are extremely useful forlocating flycatchers and identifying areas needingfollow-up visits. Loud, strong whitting may indi-cate a nearby nest, dictating that surveyors exerciseextra caution moving through the area.

Whenever a willow flycatcher (suspected orverified) is detected, be careful not to overplay thesong tape. Excessive tape playing could divert thebird from normal breeding activities, and/or at-tract the attention of predators and brood parasites.Overplaying the tape may constitute “harassment”of the flycatcher, and is not needed to verify spe-cies identification. If you have heard even a singlefitz-bew, this is sufficient for verification (althoughflycatchers usually sing repeatedly once prompted).If you have played a tape several times and a birdhas approached but has not fitz-bewed, DO NOTCONTINUE PLAYING THE TAPE. If a “po-tential” willow flycatcher responds (approaches orwhitts) but does not sing, it is best to carefully backaway and wait quietly. If it is a willow flycatcher, itwill probably sing within a short time (5 - 10 min-utes). Another option is to return to the same siteearly the following morning to listen for and/orattempt to elicit singing again.

Once a flycatcher is detected and verified, sur-veyors may continue the survey (if more surveyhabitat remains) until the entire site is completed.If continuing the survey, move 20 - 30 m past thecurrent detection before again playing the tape,and try to avoid “double-counting” flycatchers thathave already responded. Willow flycatchers mayfollow the broadcast song for 50 m or more (Soggeand Tibbitts 1994).

Looking for and Recording color bandsSeveral on-going research projects involve the

capture and banding of willow flycatchers at breed-ing sites across the southwest. In many projects,each flycatcher is banded with a unique combina-tion of small colored plastic leg bands (one or moreper leg), and a USFWS numbered aluminum band

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(which will appear silver). Surveyors may findcolor-banded individuals at their sites, and identi-fication of the band combination will provideimportant data on flycatcher movements,survivorship, and site fidelity.

To look for bands, move to get a good view ofthe flycatchers legs. This may be difficult in densevegetation, but flycatchers often perch on moreexposed branches at the edges of their territory orhabitat patch. If bands are seen, carefully note theband colors. If there is more than one band on aleg, differentiate the top (farthest up the leg) fromthe bottom (closest to the foot), and those on thebird’s left leg versus the right leg. If you are un-sure of the color, DO NOT GUESS. Instead,record the color as unknown and attempt to get abetter look during your next visit. Incorrect color-band data is worse than incomplete data, so onlyrecord colors of which you are certain. The factthat a banded bird was seen, even without beingcertain of its color combination, is very importantinformation. Record the color-band informationon the survey form, and report the sighting to theappropriate state or federal contact as soon as youreturn from the survey.

Determining the Number of Territories and PairsAccurately determining the number of breed-

ing territories and pairs is more difficult thandetermining simple presence or absence. Flycatcherhabitat is usually so dense that visual detections aredifficult, and seeing more than one bird at a timeis often impossible. Flycatchers sing from multiplesong perches within their territories, sometimesappearing to be more than one flycatcher. A fly-catcher responding to or following a surveyorplaying a tape may move considerable distances ina patch and thus be counted more than once. Resi-dent territorial male flycatchers often sing strongly,but so do many migrants and females, particularlyin response to tape-playback (Seutin 1987, Unitt1987, Sogge et al. in press). Even recently fledged(6-8 wk old) willow flycatchers may respond to atape by singing (Sogge in press). Rangewide, many

territorial male flycatchers are unmated, particu-larly those in small breeding groups (USFWS data).Clearly, each singing flycatcher may not representa territory or a mated pair.

Given sufficient time, effort and observation,it is usually possible to approximate the number ofterritories and pairs. First, determine the numberof singing individuals by listening carefully for si-multaneously singing flycatchers. Note the generallocation of each bird (aerial photographs can be useful for this purpose). Spend some time watch-ing each flycatcher to determine approximateboundaries of its territory, and to determine if andhow it interacts with other flycatchers. If one ormore singing birds stay primarily in mutually ex-clusive areas, they can be considered as separateterritories. To determine if a flycatcher is paired,watch for interactions within a territory. Refer tothe Determining Breeding Status section thatfollows for signs of pairing and breeding activity.Do not report a territorial male as a pair unlessyou observe one or more of the signs listed below.In some cases, it may be possible only to estimatethe number of singing individuals. In others, it maytake multiple site visits to differentiate territoriesor pairs.

Determining Breeding StatusOne way to determine if the flycatchers found

at a particular site are migrants or territorial is tofind out if they are still present during the “non-migrant” period, which is generally from about15 June - 20 July (refer to Figure 4 [page 13]; Unitt1987). A willow flycatcher found during this timeis probably a resident bird on a territory (althoughthere is a small chance it could be a non-territorial“floater”; Sogge and Tibbitts 1994, Sogge et al. inpress). If the management question is simplywhether the site is a potential breeding area, docu-menting the presence of a territorial flycatcherduring this time period may meet all surveyobjectives, and the site may not need to be re-surveyed during the remainder of that breedingseason.

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However, in some cases it may be importantto determine whether breeding and nesting effortsare actually taking place. At many currently knownbreeding sites, some males maintain territories wellinto July yet never succeed in attracting a mate(Sogge 1995b, Petterson and Sogge 1996, Sferra etal. 1997). Thus, an assumption that a singing malerepresents a breeding pair may not be well founded(especially in small populations).

The best way to determine whether a pair ispresent and breeding is to move a short distanceaway from where the bird was sighted, find a goodvantage point, and sit or lie quietly to watch forsigns of breeding activity. Signs of breeding activ-ity include:

a) observation of another “unchallenged” wil-low flycatcher in the immediate vicinity(indicates possible pair);

b) whitt calls between nearby flycatchers (indi-cates possible pair);

c) interaction twitter calls between nearby fly-catchers (indicates possible pair);

d) countersinging or physical aggression againstanother flycatcher or bird species (suggeststerritorial defense);

e) physical aggression against cowbirds (sug-gests nest defense);

f) observation of willow flycatchers copulat-ing;

g) flycatcher carrying nest material (verifiesnesting attempt, but not nest outcome);

h) flycatcher carrying food or fecal sac (veri-fies nest with young, but not nest outcome);

i) locating an active nest (see special consider-ations section above);

j) observation of adult flycatchers feedingfledged young (verifies successful nesting).

You may be able to detect flycatcher nestingactivity, especially once the chicks are being fed.Adults feed chicks at rates of up to 30 times perhour (Sogge 1995b), and the repeated trips to thenest tree or bush are often quite evident. Be sureto note on the flycatcher survey form any breed-ing activity that is observed, including detailed

descriptions of the number of birds, specific ac-tivities observed, etc. Also note the location ofbreeding activities on an aerial photograph, map,or sketch of the area.

The number of flycatchers found at a site canalso provide a clue as to whether they are migrantsor territorial residents. Early season detections ofsingle, isolated willow flycatchers often (but notalways) turn out to be migrants. On the other hand,discovery of a number of willow flycatchers at onesite usually (but not always) leads to verificationthat at least some of them remain as breeders. Thisunderscores the importance of completing a thor-ough survey of each site to be confident of theapproximate number of flycatchers present.

Documenting Presence of CowbirdsBrown-headed cowbirds significantly impact

many southwestern willow flycatcher populationsby decreasing or eliminating flycatcher productiv-ity, nesting success, and juvenile survival (Unitt1987, Brown 1988, Whitfield 1990, USFWS 1993,Sogge 1995a and b, Whitfield and Strong 1995,Sferra et al. 1997, Sogge et al. in press). It is im-portant to document if cowbirds occur at aflycatcher breeding site to determine if those fly-catchers are at risk from cowbird brood parasitism.As noted earlier, another reason to watch for cow-birds is to avoid attracting cowbirds to a flycatcherterritory or making flycatcher nests more detect-able to cowbirds.

Surveyors should look and listen for cowbirdsat, and in the vicinity of, the survey site. Thisrequires that surveyors are able to identify cow-birds by sight and vocalizations. The latter isparticularly important because cowbirds are oftenheard even when not seen in the dense habitatat flycatcher sites. Accurate estimation of cow-bird numbers at a site is often difficult. Cow-birds may be either very inconspicuous or veryprominent. They often travel in groups, withindividuals and groups ranging over wide areasduring short periods of time. A count may behigh or low depending on the activities of a cow-

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bird flock ranging in the area. Because of thedifficulty in accurately estimating cowbird abun-dance, the flycatcher survey form requests simplepresence/absence data. A relative estimate of cow-bird abundance can be included in the commentsection.

Reporting ResultsFill in all appropriate information on the

willow flycatcher survey form while still in the field,and mark the location of detections on a copy ofthe USGS topographic map. Make a habit ofreviewing the form before you leave any site—trying to remember specific information andrecording it later leads to missing and inaccuratedata. Put the location of the sighting on an aerialphotograph or sketch of the site. Whenever awillow flycatcher territory or nest site is confirmed,

notify the USFWS or appropriate state wildlifeagency (see Contacts section, page 29) as soon asyou return from the field.

Complete a survey form (Appendix 1) for eachsite surveyed, whether or not flycatchers aredetected. “Negative data” (e.g., a lack of detec-tions) is important to document absence of willowflycatchers and help determine what areas havealready been surveyed. Make and retain a copyof each survey form, and submit the original.Survey forms must be returned to the USFWSand/or the appropriate wildlife agency by the speci-fied deadline. Contact the appropriate agency eachyear to find out the submission deadline date.Timely submission of survey data is a permitrequirement, and will ensure the informationis included in annual statewide and regionalreports.

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This survey protocol is based primarily onthe earlier southwestern willow flycatcher sur-vey protocol (Tibbitts et al. 1994), and owesmuch to previous U.S. Forest Service guidelines(Craig et al. 1992). The experience and insightsof literally dozens of surveyors contributedgreatly to the development of this protocol—we are grateful to all of them. The authors greatlyappreciate the technical advice and assistance ofWilliam Haas, Phillip Unitt, and Mary Whitfield.Helpful reviews were provided by Darrell

ACKNOWLEDGMENTS

Ahlers, Troy Corman, Charles Drost, WilliamHaas, Jen Owen, Eben Paxton, Ingri Quon, JayRourke, Linda Sogge, and Mary Whitfield.Unpublished data was graciously provided byWilliam Haas, Thomas Huels, RobertMcKernan, and Mary Whitfield. The coverillustration was drawn by Troy Corman. TheArizona Game and Fish Department, U.S.Bureau of Reclamation, and U.S. GeologicalSurvey contributed funds for preparation anddistribution of this report.

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Contacts : Personnel at the following agencies can be contacted for information about willowflycatcher survey training, research permits, and to report flycatcher detections.

STATE AGENCIES

Arizona Game and Fish Dept. 602/789-3589Nongame Branch2221 W. Greenway Rd.Phoenix, AZ 85023

California Dept. of Fish and Game 916/653-76641416 Ninth StreetSacramento, CA 95814

Colorado Division of Wildlife 970/247-0855151 E. 16th StDurango, CO 81301

Nevada Division of Wildlife 702/688-1500Box 10678Reno, NV 89520

New Mexico Dept. of Game & Fish 505/827-9904Endangered Species ProgramVillagra BuildingSanta Fe, NM 87503

Texas Parks and Wildlife Dept. 512/389-48003000 IH-35 South, Suite 100Austin, TX 78704

Utah Div. of Wildlife Resources 801/538-4764Nongame Avian Program Coordinator1596 West North TempleSalt Lake City, UT 84116

FEDERAL AGENCIES

U.S. Fish and Wildlife Service:

Region 1 (includes CA, NV) 503/231-2063911 NE 11th Ave, Portland, OR 97232

CA Carlsbad Field Office 760/431-94402730 Loker AveCarlsbad, CA 92008

Sacramento Field Office 916/979-27102800 Cottage Way, Rm. E-1803Sacramento, CA 95825

Ventura Field Office 805/644-17662493 Portola Rd, Suite BVentura, CA 93003

NV Nevada State Office 702/784-52274600 Kietzke Ln, Bldg C, Rm 125Reno, NV 89502

Region 2 (includes AZ, NM, TX): 505/248-6647P. O. Box 1306, Albuquerque, NM 87103

AZ AZ Ecological Services 602/640-27202321 W. Royal Palm Rd, Suite 103Phoenix, AZ 85021

NM NM Ecological Services 505/761-45253530 Pan American Hwy. NE, Suite DAlbuquerque, NM 87107

TX 611 E. 6th St., Suite 407 512/389-4505Austin, TX 78701

Region 6 (includes CO, UT) 303/236-7904P.O. Box 25486, Denver Federal CenterDenver, CO 80225

C O 764 Horizon Dr, South Annex A 970/243-2778Grand Junction, CO 81506

UT Lincoln Plaza, Suite 404 801/524-5001145 East 1300 SouthSalt Lake City, UT 84115

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Aldrich, J. W. 1951. A review of the races of theTraill’s flycatcher. Wilson Bulletin 63:192-197.

Arizona Game and Fish Department. In prep.Wildlife species of concern in Arizona. Ari-zona Game and Fish Department. Phoenix,Arizona.

Behle, W. H. and H. G. Higgins. 1959. The birdsof Glen Canyon. Pp. 107-133 in Ecologicalstudies of flora and fauna in Glen Canyon (A.M. Woodbury, ed.). University of Utah An-thropological Paper 40 (Glen Canyon SeriesNo. 7).

Bibby, C.J., N.D. Burgess and D.A. Hill. 1992.Bird census techniques. Academic Press, Lon-don. 257 pp.

Brown, B. T. 1988. Breeding ecology of a willowflycatcher population in Grand Canyon, Ari-zona. Western Birds 19 (1):25-33.

Browning, M. R. 1993. Comments on the tax-onomy of Empidonax traillii (willow flycatcher).Western Birds 24:241-257.

California Department of Fish and Game. 1991.Endangered and threatened animals of Cali-fornia. State of California, The ResourcesAgency, Department of Fish and Game. Sac-ramento, California. 5 pp.

Cannon, R. W. and F. L. Knopf. 1984. Speciescomposition of a willow community relativeto seasonal grazing histories in Colorado.Southwestern Naturalist 29:234-237.

Craig, D., R. Schlorff, B. Valentine, and C. Pelles.1992. Draft survey protocol for willow fly-catchers (Empidonax traillii) on National ForestService lands in the Pacific Southwest region.USDA Forest Service. 13 pp.

Dahl, T. E. 1990. Wetlands losses in the UnitedStates, 1780s to 1980s. U.S. Department ofthe Interior, Fish and Wildlife Service, Wash-ington, D.C. 13 pp.

Flett, M.A. and S.D. Sanders. 1987. Ecology of aSierra Nevada population of willow flycatch-ers. Western Birds 18:37-42.

Garret, K. and J. Dunn. 1981. Birds of SouthernCalifornia: status and distribution. Los Ange-les Audubon Society, Los Angeles, California.

General Accounting Office. 1988. Public range-lands: Some riparian areas restored butwidespread improvement will be slow. Gen-eral Accounting Office, U.S. Government.Washington, D.C.

Harris, J. H. 1991. Effects of brood parasitism bybrown-headed cowbirds on willow flycatchernesting success along the Kern River, Califor-nia. Western Birds 22 (1):13-26.

Harris, J. H., S. D. Sanders, and M. A. Flett. 1988.The status and distribution of the willow fly-catcher (Empidonax traillii) in the Sierra Nevada.California Department of Fish and Game,Wildlife Management Branch AdministrativeReport 88-1.

Howell, S.N.G. and S. Webb. 1995. A guide tothe birds of Mexico and northern centralAmerica. Oxford University Press, New York.851 pp.

Hubbard, J. P. 1987. The status of the willowflycatcher in New Mexico. Endangered SpeciesProgram, New Mexico Department of Gameand Fish, Santa Fe, New Mexico. 29 pp.

LITERATURE CITED

32


Oberholser, H. C. 1974. The bird life of Texas.University of Texas Press, Austin, Texas. 1069 pp.

Paxton, E., J. Owen and M.K. Sogge. 1996.Southwestern willow flycatcher response tocatastrophic habitat loss. U.S.G.S. ColoradoPlateau Research Station/Northern ArizonaUniversity report. 12 pp.

Peterson, R.T. 1990. A field guide to westernbirds. 3rd ed. Houghton Mifflin Company,Boston, Massachusetts. 432 pp.

Petterson, J.R. and M.K. Sogge. 1996. Distribu-tion and breeding productivity of thesouthwestern willow flycatcher along the Colo-rado River in the Grand Canyon—1996.Summary report. Grand Canyon National Parkand National Biological Service Colorado Pla-teau Research Station/Northern ArizonaUniversity. 30 pp.

Phillips, A. R. 1948. Geographic variation inEmpidonax traillii. Auk 65:507-514.

Phillips, A. R., J. Marshall, and G. Monson. 1964.The birds of Arizona. University of ArizonaPress, Tucson, Arizona. 212 pp.

Pulliam, H.R. 1988. Sources, sinks, and popu-lation regulation. American Naturalist132:652-661.

Reed, J.M. 1996. Using statistical probability toincrease confidence of inferring species extinc-tion. Conservation Biology 10:1283-1285.

Ridgely, R.S. and G. Tudor. 1994. The birds ofSouth America; suboscine passerines. Univer-sity of Texas Press, Austin, Texas. 814 pp.

Rowley, J. S. 1930. Observations on the dwarfcowbird. Condor 32:130.

Johnson, R. R., and L. T. Haight. 1984. Ripar-ian problems and initiatives in the AmericanSouthwest: a regional perspective. Pp. 404-412in California riparian systems: ecology, con-servation, and productive management (R.E.Warner and K.M. Hendrix, eds.). Universityof California Press, Berkeley. 1035 pp.

Johnson, R. R., L. T. Haight, and J. M. Simpson.1987. Endangered habitats versus endangeredspecies: a management challenge. WesternBirds 18:89-96.

Katibah, E. F. 1984. A brief history of riparianforests in the Central Valley of California. Pp.23-29 in California riparian systems: ecology,conservation, and productive management(R.E. Warner and K.M. Hendrix, eds.). Uni-versity of California Press, Berkeley. 1034 pp.

Maynard, W.R. 1995. Summary of 1994 surveyefforts in New Mexico for southwestern wil-low flycatcher (Empidonax traillii extimus).Contract #94-516-69. New Mexico Depart-ment of Game and Fish, Santa Fe, NM. 48 pp.

McCabe, R. A. 1991. The little green bird: ecol-ogy of the willow flycatcher. PalmerPublications, Inc., Amherst, Wisconsin. 171 pp.

Monson, G. and A. R. Phillips. 1981. Annotatedchecklist of the birds of Arizona. Universityof Arizona Press, Tucson, Arizona. 240 pp.

Muiznieks, B. D., T. E. Corman, S. J. Sferra, M.␣K.Sogge, and T. J. Tibbitts. 1994. Arizona Part-ners in Flight southwestern willow flycatchersurvey, 1993. Arizona Game and Fish Depart-ment report. Phoenix, Arizona.

New Mexico Department of Game and Fish.1996. List of threatened and endangered.Amendment No. 1, NMAC 33.1; 31 January1996. New Mexico Department of Game andFish, Santa Fe, New Mexico.

33


San Diego Natural History Museum. 1995. Un-published summary of willow flycatcherbreeding ecology, distributed during southwest-ern willow flycatcher conference, November1995.

Schlorff, R. W. 1990. Status review of the willowflycatcher (Empidonax traillii) in California.Report to the California Department of Fishand Game, Department Candidate SpeciesStatus Report 90-1. 23 pp.

Serena, M. 1982. The status and distribution ofthe willow flycatcher (Empidonax traillii) inselected portions of the Sierra Nevada, 1982.California Department of Fish and Game,Wildlife Management Branch AdministrativeReport 82-5.

Seutin, G. 1987. Female song in Willow Fly-catchers (Empidonax traillii). Auk 104: 329-330.

Sferra, S.J., R.A. Meyer and T.E. Corman. 1995.Arizona Partners in Flight 1994 southwesternwillow flycatcher survey. Final technical re-port 69. Arizona Game and Fish Department,Nongame and Endangered Wildlife Program.Phoenix, Arizona. 46 pp.

Sferra, S.J., T.E. Corman, C.E. Paradzick, J.W.Rourke, J.A. Spencer and M.W. Sumner. 1997.Arizona Partners in Flight southwestern willowflycatcher survey: 1993-1996 summary report.Technical Report 113. Arizona Game and FishDepartment, Nongame and Endangered Wild-life Program. Phoenix, Arizona. 46 pp.

Skaggs, R.W. 1995. Population size, breedingbiology, and habitat of willow flycatchers inthe Cliff-Gila Valley, New Mexico—1995. FinalReport. New Mexico Department of Gameand Fish. 38 pp.

Sogge, M. K. and T. J. Tibbitts. 1992. Southwest-ern willow flycatcher (Empidonax traillii extimus)surveys along the Colorado River in GrandCanyon National Park and Glen Canyon Na-tional Recreation Area—1992 summary report.National Park Service Cooperative Park Stud-ies Unit/Northern Arizona University and U.S.Fish and Wildlife Service report. 46 pp.

Sogge, M. K., T. J. Tibbitts, and S. J. Sferra. 1993.Status of the southwestern willow flycatcheralong the Colorado River between Glen Can-yon Dam and Lake Mead—1993. Summaryreport. National Park Service Cooperative ParkStudies Unit/Northern Arizona University,U.S. Fish and Wildlife Service, and ArizonaGame and Fish Department report. 69 pp.

Sogge, M.K. and T.J. Tibbitts. 1994. Distributionand status of the southwestern willow flycatcheralong the Colorado River in the Grand Can-yon—1994. Summary report. NationalBiological Service Colorado Plateau ResearchStation/Northern Arizona University and U.S.Fish and Wildlife Service, Phoenix. 37 pp.

Sogge, M.K. 1995a. Southwestern willow fly-catchers in the Grand Canyon. Pages 89-91 inLaRoe, E.T., G.S. Farris, C.E. Puckett, P.D.Doran, and M.J. Mac, eds. 1995. Our livingresources: a report to the nation on the distri-bution, abundance, and health of U.S. plants,animals, and ecosystems. U.S. Department ofthe Interior, National Biological Service, Wash-ington, DC. 520 pp.

Sogge, M.K. 1995b. Southwestern willow fly-catcher (Empidonax traillii extimus) monitoringat Tuzigoot National Monument. 1995progress report to the National Park Service.National Biological Service Colorado PlateauResearch Station/Northern Arizona Univer-sity report. 20 pp.

34


Sogge, M.K., T.J. Tibbitts, C. van Riper III, and T.May. 1995. Status of the southwestern willowflycatcher along the Colorado River in GrandCanyon National Park—1995. Summaryreport. National Biological Service ColoradoPlateau Research Station/Northern ArizonaUniversity. 26 pp.

Sogge, M.K. In press. Primary song by a juvenilewillow flycatcher. Journal of Field Ornithology.

Sogge, M.K., T.J. Tibbitts and J.R. Petterson. Inpress. Status and ecology of the SouthwesternWillow Flycatcher in the Grand Canyon.Western Birds.

Spencer, J.A., S.J. Sferra, T.E. Corman, J.W.Rourke, and M.W. Sumner. 1996. ArizonaPartners in Flight 1995 southwestern willowflycatcher survey. Technical report 79. Ari-zona Game and Fish Department, Nongameand Endangered Wildlife Program. Phoenix,Arizona. 46 pp.

State of Arizona. 1990. Final report and recom-mendations of the Governor’s riparian habitattask force. Executive Order 89-16. Streamsand riparian resources. Phoenix, Arizona.October 1990. 28 pp.

Stein, R.C. 1963. Isolating mechanisms betweenpopulations of Traill’s flycatcher. Proc. Am.Philo. Soc. 107:21-50.

Stiles, F.G. and A.F. Skutch. 1989. A guide to thebirds of Costa Rica. Comstock, Ithaca, NewYork. 364 pp.

Taylor, D. M. and C. D. Littlefield. 1986. Willowflycatcher and yellow warbler response to cattlegrazing. American Birds 40:1169-1173.

Tibbitts, T.J., M.K. Sogge, and S.J. Sferra. 1994.A Survey Protocol for the Southwestern Wil-low Flycatcher (Empidonax traillii extimus).National Park Service Technical Report NPS/NAUCPRS/NRTR-94/04.

Unitt, P. 1987. Empidonax traillii extimus: an en-dangered subspecies. Western Birds18(3):137-162.

U.S. Fish and Wildlife Service. 1991. Notice ofreview: animal candidate review for listing asendangered or threatened species. November21, 1991, Federal Register 56:58804-58836.

U.S. Fish and Wildlife Service. 1992. Notice of90-day finding on petition to list the south-western willow flycatcher as an endangeredspecies. September 1, 1992, Federal Register57:39664-39668.

U.S. Fish and Wildlife Service. 1993. Proposal tolist the southwestern willow flycatcher as anendangered species and to designate criticalhabitat. July 23, 1993, Federal Register58:39495-39522.

U.S. Fish and Wildlife Service. 1995. Final RuleDetermining Endangered Status for the South-western Willow Flycatcher. Federal Register60: 10694 (February 27, 1995).

Utah Division of Wildlife Resources. 1997. UtahSensitive Species List—March 1997. Utah Di-vision of Wildlife Resources, Salt Lake City,Utah. 28 pp.

Verner, J. 1985. Assessment of counting tech-niques. Pp. 247-302 in Current Ornithology,Volume 2. R.F. Johnston (ed.). Plenum Press,NY. 364 pp.

35


Whitfield, M. J. 1990. Willow flycatcher repro-ductive response to brown-headed cowbirdparasitism. Masters Thesis, California StateUniversity, Chico, California. 25 pp.

Whitfield , M.J. and C.M. Strong. 1995. A brown-headed cowbird control program andmonitoring for the southwestern willow fly-catcher, South Fork Kern River, California.California Department of Fish and Game, Birdand Mammal Conservation Program Report95-4, Sacramento, California. 17 pp.

Whitfield, M.J. and K.M. Enos. 1996. A brown-headed cowbird control program andmonitoring for the southwestern willow

flycatcher, south fork Kern River, California—1996. California Department of Fish andGame Report, Sacramento, California. 14 pp.

Wiens, J.A. 1989. The ecology of bird communi-ties. Volumes 1 and 2. Cambridge UniversityPress, Cambridge.

Wiens, J.A. 1996. Wildlife populations in patchyenvironments: metapopulations, mosaics, andmanagement. Pages 53-84 in McCullough,D.R. (Ed). Metapopulations and wildlife con-servation. Island Press, Washington, D.C.

Wilbur, S. R. 1987. Birds of Baja California. Uni-versity of California Press, Berkeley, California.

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Appendix 1

Willow Flycatcher Survey and Detection Form (rev. 4/98)

A Southwestern Willow Flycatcher Natural History Summary ......A Southwestern Willow Flycatcher...

Documents

Transcript of A Southwestern Willow Flycatcher Natural History Summary ......A Southwestern Willow Flycatcher...