Studies in Avian Biology No. 26:41±51, 2003.

WILLOW FLYCATCHER WINTER HABITAT IN EL SALVADOR, , AND PANAMA: CHARACTERISTICS AND THREATS

JANET C. LYNN,THOMAS J. KORONKIEWICZ,MARY J. WHITFIELD, AND MARK K. SOGGE

Abstract. The Willow Flycatcher (Empidonax traillii) spends more than half the year on wintering grounds from central Mexico to northern South America, yet there is little detailed information about Willow Flycatcher winter distribution and habitat use. We surveyed for wintering Willow Flycatchers in El Salvador, Costa Rica, and Panama during January and February of 1998±2000. Our objectives were to locate and describe occupied Willow Flycatcher winter habitat and identify possible threats to wintering ¯ycatchers and their habitats. We detected 542 wintering Willow Flycatchers distributed among 28 survey locations. The majority of occupied winter Willow Flycatcher habitat was found along the Paci®c lowlands below 250 m, and contained four main habitat components: standing or slow moving freshwater and/or saturated soil; patches and/or stringers of trees; woody shrubs; and open areas. Large and small-scale agricultural activities and/or cattle ranching were present near most occupied sites, resulting in a matrix of relatively small and fragmented patches of suitable wintering habitat within a larger agriculture-dominated landscape. Key Words: Central America; distribution; Empidonax traillii; surveys; threats; Willow Flycatcher; winter habitat. Sinopsis. El Mosquerito de Traill (Empidonax traillii) pasa la mitad del anÄo en tierras invernales desde centro de MeÂxico al norte de Sur AmeÂrica, sin embargo, hay pocas informacioÂn detallada acerca de la distribucioÂn invernal del mosquerito de traill y del uso del habitat. Estuvimos estudiando Mos- queritos de Traill invernales en El Salvador, Costa Rica y Panama durante enero y febrero de 1998± 2000. Nuestros objetivos eran localizar y describir habitats invernales ocupados por mosqueritos de traill e identi®car posibles amenazas a mosqueritos de traill y sus habitats. Detectamos 542 mosqueritos de traill invernales distribuidos entre 28 lugares de rastreo. La mayorõÂa de habitats ocupados por Mosqueritos de Traill invernales se hallaron a lo largo de las tierras bajas a menos de 250 metros, y contenõÂan cuatro componentes principales de habitat: agua fresca detenida o de lento correr y/o terreno saturado; manchas y/o ®las de aÂrboles; arbustos lenÄosos; y regiones abiertas. Cerca de la mayorõÂa de lugares ocupados se encontraron actividades agrõÂcolas en escalas grandes o pequenÄas, dando asõ como resultado una matriz de manchas relativamente pequenÄas y fragmentadas de habitat invernal adecuado dentro de un terreno dominado por una mayor actividad agrõÂcola.

A nearctic-neotropical migrant, the Willow Fly- tinguish between Willow Flycatchers and Alder catcher (Empidonax traillii) spends the majority Flycatchers (E. alnorum), lumping the two as of the year migrating and wintering in subtropical ``Traill's Flycatcher.'' As a result, we know much and tropical areas of the Paci®c slope of central less about Willow Flycatcher habitat use in winter Mexico, Central America, and northern South than in the breeding season, where most studies America, where they have been reported in moist to date have been focused. thickets, dry shrubby areas, and woodland bor- Growing human populations and demands on ders in humid to semi-arid partially open areas natural resources throughout the tropics pose (Meyer de Schauensee and Phelps 1978, Ridgely threats to the winter habitats of many neotropical and Gwynne 1989, Stiles and Skutch 1989, Rid- migrants (Terborgh 1989), including the Willow gely and Tudor 1994, Howell and Webb 1995, Flycatcher. Although a topic of concern (Morse Unitt 1997, Edwards 1998). Stotz et al. (1996) 1980, Holmes and Sherry 1992), the availability associated Willow Flycatchers with tropical low- of wintering habitat, and the nature and extent land evergreen and secondary forests and second- of impacts and threats to that habitat, have re- growth scrub along the Paci®c Arid Slope and the ceived little research attention. Central America Gulf-Caribbean Slope of Central America. Gorski has experienced a long history of disturbance (1969) found wintering Willow Flycatchers in from various land use practices, and high rates Panama along transitional zones containing of deforestation and growing human populations shrubs and open grassy areas, usually in close have caused dramatic changes to the Paci®c proximity to water. Rand and Traylor (1954) re- lowlands, which comprise the majority of the ported that ¯ycatchers wintering in El Salvador winter range of the Willow Flycatcher. Although used low perches in bushes and short trees within deforestation and slash-and-burn agriculture forested and thicketed areas. Most of the above were practiced in some areas during pre-con- descriptions do not differentiate between migra- quest periods (Katz 1972, Coates 1997), the ar- tion and wintering habitat, and some do not dis- rival of the Spanish in the 1500s initiated larger- 41 42 STUDIES IN AVIAN BIOLOGY NO. 26 scale changes through the introduction of inten- more surveys at each site. Site selection was in¯uenced sive agricultural techniques and livestock. Even by accessibility, and limited to sites readily accessible greater landscape changes, including some of by roads, rivers, or other transportation corridors. the highest rates of deforestation worldwide, HABITAT SURVEYED have occurred in the past 40±60 years in asso- ciation with rapid human population growth We surveyed a variety of habitat types including dry (Jones 1990, Houghton et al. 1991, Hartshorn uplands with patches or stringers (narrow strips, typi- 1992). cally only a few individuals wide) of trees and/or Because habitat loss on winter ranges can in- woody shrubs bordered by savannas, pasture land, and agricultural areas; quebradas (streams), rivers, and es- ¯uence some neotropical migrant populations teros (meandering oxbow waterways) bordered by gal- (Terborgh 1989, Morton 1992, Rappole et al. lery forests and woodlands comprised of patches or 1992, Robbins et al. 1992), it is important to stringers of trees and woody shrubs; lagunas (inter- identify changes in land use patterns and their mittent freshwater wetlands) and seeps bordered by effects on winter habitat. This, coupled with a patches or stringers of trees and woody shrubs; sea- better understanding of Willow Flycatcher win- sonally inundated savannas and pasture land contain- ter habitat characteristics and the landscape and ing patches and/or stringers of trees and woody shrubs; human-use context in which that habitat occurs, Parkinsonia spp. dominated freshwater wetlands; res- can supply insight into possible limiting factors ervoirs and sections of the Panama Canal; brackish tidal wetlands and mangroves; and lowland tropical affecting ¯ycatcher populations. To gather more deciduous and evergreen forest interior and edges. detailed information on the distribution and sta- tus of winter Willow Flycatcher habitat and to SURVEY TECHNIQUE identify potential threats to that habitat, we sur- veyed for wintering ¯ycatchers in portions of We conducted surveys during January and February of 1998±2000. Surveys were primarily performed be- Central America for three consecutive wintering tween 0600±1000 hrs (N ϭ 142) and 1600±1800 hrs periods. Our objectives were to locate and de- (N ϭ 12) when Willow Flycatcher activity and re- scribe occupied ¯ycatcher habitat, identify com- sponse to tape playback are greatest (Gorski 1969). At mon habitat elements, and characterize potential each site, we initially listened quietly (1±3 min) for threats to wintering ¯ycatchers and their habi- spontaneous singing, then broadcast Willow Flycatcher tats. vocalizations, using a hand-held tape player, at a vol- ume similar to that of a naturally singing bird. The METHODS tape was played for 15±30 sec, followed by a 1±4 min STUDY AREA listening period (in 2000, this was repeated twice at We conducted surveys in El Salvador, Costa Rica, every broadcast point). Surveyors walked transects and Panama, primarily along Central America's Paci®c through or along the vegetation whenever possible and lowlands, with some locations along the Caribbean repeated the procedure every 20±40 m. coast and Canal Zone in Panama. Latitudes ranged If a Willow Flycatcher was observed but did not from 13Њ 48Ј N along the Rio Paz at the Guatemala respond with song to the tape playback, we stood qui- and El Salvador border to 7Њ26ЈN at TonosõÂ along the etly for up to 5 min before broadcasting a second tape. Azuero Peninsula of Panama. Longitudes extended This tape included a variety of Willow Flycatcher from 90Њ7ЈW in El Salvador to 77Њ43ЈW at El Real in whits and creets/breets, wee-oos, churr/kitters, and a the Darien region in Panama. Elevations ranged from set of interaction calls given by a mated pair of Willow sea level to 2000 m, with the majority of sites below Flycatchers. These calls were frequently effective in 250 m. Annually, the Paci®c lowlands experience two eliciting a ®tz-bew song, thereby enabling surveyors to distinct seasons of roughly equal duration. Invierno positively identify Willow Flycatchers. Sites were only (the rainy season) occurs from May/June until Novem- considered Willow Flycatcher habitat if a ®tz-bew vo- ber/December, and verano (the dry season) extends calization was heard. from December/January until April/May. The Carib- At each survey site, we recorded distance and di- bean coast of Panama experiences a later and shorter rection to the nearest landmark, geographical coordi- dry season than does the Paci®c slope, ranging from nates (using hand-held GPS units), land ownership and January to April. management (if discernable), elevation, and length of each survey transect. We also recorded general habitat SELECTION OF SURVEY LOCATIONS characteristics including distance to surface water and/ We selected locations at which to survey for win- or saturated soil, dominant tree and plant species, es- tering Willow Flycatchers based on museum specimen timated canopy height, and topography. Genus and collection locations and dates (per Unitt 1997), reports species of trees, shrubs, and herbaceous vegetation in the literature, banding records, and recent observa- were noted when known. We recorded time and loca- tions by local bird enthusiasts and ornithologists. Due tion of Willow Flycatcher detections; during 1998 and to the paucity of records along the Caribbean coast and 1999 Costa Rica surveys, we noted whether each ¯y- central highlands, survey locations were concentrated catcher was detected before or after the tape broadcast, along the Paci®c lowlands. Within each location or and type of initial and subsequent response to playback general geographic area, we selected several speci®c during the survey. In cases where a site was surveyed sites (e.g., patches of habitat) and conducted one or in more than one year, we report only the results for WILLOW FLYCATCHER WINTER HABITATÐLynn et al. 43

FIGURE 1. Willow Flycatcher winter survey locations in El Salvador, Costa Rica, and Panama. Dots indicate areas with one location; stars indicate areas with two locations.

the year with the largest number of ¯ycatcher detec- HABITAT CHARACTERISTICS tions. Occupied winter Willow Flycatcher habitat RESULTS was characterized by four main habitat compo- SURVEY EFFORTS nents: (1) standing or slow moving freshwater and/or saturated soils; (2) patches or stringers of We surveyed a total of 42 survey locations trees; (3) woody shrubs; and (4) open areas such between 1998 and 2000: 10 in El Salvador, 20 as pastures, savannas, or bodies of water bor- in Costa Rica, and 12 in Panama (Fig. 1; Ap- dering forest edges (Fig. 2). With the exception pendix). We conducted surveys at 154 different of three sites in El Salvador, no ¯ycatchers were survey sites for a total of 561 survey hrs. We found at survey locations lacking one or more detected 542 Willow Flycatchers at 28 of the 42 survey locations; approximately half (N ϭ 274) of these major habitat components. All occupied of the total ¯ycatcher detections occurred in El habitats were situated in low-lying areas that ex- Salvador, despite fewer survey hours spent in perience seasonal inundation during the rainy that country (Appendix). We found ¯ycatchers season, when ¯ycatchers generally arrive at the at 75% of the historical locations we surveyed. wintering sites. Habitat types in which we did not detect ¯ycatchers included dry uplands, RESPONSE TO TAPE PLAYBACK woodlands and forests along fast moving Flycatchers responding to tape-playback gave streams and rivers, Parkinsonia-dominated a variety of vocalizations including (per vocali- freshwater wetlands, brackish tidal wetlands and zation terminology of Stein 1963 and Gorski mangroves, and forest interior. Occupied ¯y- 1969) ®tz-bews, whitts, wheeps, creets/breets, catcher habitats ranged in elevation from 0±250 and churr/kitters. In Costa Rica during 1998 and m. We did not detect Willow Flycatchers at sur- 1999, 70% of ¯ycatchers initially responded by vey sites at the two higher elevation locations calling (whitts or wheeps) and 30% gave the (Lago Coatepeque, El Salvador [730 m], and characteristic ®tz-bew song. When we continued , Costa Rica [Ͼ2000 m]), which con- to broadcast vocalizations in the immediate tained all four of the winter habitat components. proximity of calling ¯ycatchers, 60% of calling The freshwater/saturated soil component at ¯ycatchers eventually sang. Thus, overall, 70% occupied sites consisted of lagunas, muddy of detected Willow Flycatchers sang in response seeps, esteros, slow-moving quebradas, reser- to tape-playback. Flycatchers were generally voirs, and associated ¯oodplain areas that con- most responsive prior to 1000 hrs. tained aquatic and emergent vegetation. Al- 44 STUDIES IN AVIAN BIOLOGY NO. 26

FIGURE 2. Willow Flycatcher winter habitat at Laguna de Olomega, El Salvador, showing the four main habitat components of standing freshwater, woody shrubs, patches of trees, and open areas. though they varied greatly in size and shape, 74 such as deforestation and burning were evident. of the 77 occupied sites retained water into the Land-altering practices seen at survey sites in- dry season when surveys were conducted; la- cluded cattle grazing, small- and large-scale ag- gunas, esteros, and reservoirs contained water riculture, draining of wetlands via irrigation ca- year-round. Wet areas were typically bordered nals, woodcutting for fuel, logging, urban ex- by woody and herbaceous shrubs (primarily Mi- pansion, and erosion. During surveys in Costa mosa sp.), patches or stringers of trees, savanna- Rica, two occupied ¯ycatcher sites were de- woodland edges, second-growth woodlands, stroyed; one was bulldozed shortly after we sur- pasture lands, and/or agricultural areas. Woody veyed the site, the other cut down while we were shrubs were generally 1±3 m high and ranged trying to capture and band ¯ycatchers (Fig. 3). from dense impenetrable thickets to sparse and Both areas were converted to short grass pasture. widely scattered in distribution. The tree com- Evidence of cattle grazing was seen in and ponent consisted primarily of deciduous species, around 127 of the 154 survey sites, including although in wetland areas trees usually retained 92% of occupied sites (Table 1). Although most of their leaves throughout the year. Aver- heavily de®ned cattle trails were common, the age canopy height of tree patches and stringers intensity of grazing and its effects on ¯ycatcher ranged from 6±15 m, with emergent trees such habitat varied among occupied sites. We found as large guanacaste (Enterlobium cyclocarpum) Willow Flycatchers at some sites where cattle and ceiba (Ceiba pentandra) ranging from 20± grazed among scattered shrubs, small trees, and/ 35 m in height. Except for reservoirs and along the Panama Canal, seasonal ¯ooding inundated or patches of mixed herbaceous vegetation, but the bordering ¯oodplains and vegetation. Al- not at grazed sites where woody vegetation was though these inundated areas contained standing absent. water through October or November, the sites Agricultural crops from small-scale and large- and bordering ¯oodplains tended to dry up as scale farms were grown within 200 m of 69 of the dry season progressed. the 154 survey sites, including 39% of occupied sites (Table 1). Agricultural and silvicultural THREATS crops found at survey sites included sugar cane, All of the sites occupied by Willow Flycatch- oil palm, rice, teak, and other commercial crops, ers had been altered by historical and current as well as crops grown on small subsistence human activity, and many were relatively small farms such as sorghum, corn, beans, and melons. areas surrounded by altered landscapes that con- Large-scale commercial crops dominated large tinue to encroach on remnant ``natural'' habitat. areas of lowland landscapes, and occupied win- Sites were heavily disturbed, and human impacts ter habitats generally remained only as small WILLOW FLYCATCHER WINTER HABITATÐLynn et al. 45 fragmented patches surrounded by agricultural was always found near freshwater lagunas, land (Fig. 4). lakes, marshes, wetlands, slow moving rivers or Trash and pollutants, such as plastic contain- streams, and seasonally inundated savannas and ers and bags, gasoline, and laundry and dish de- pastures. The only exceptions occurred at three tergents, were present in and around rivers, survey sites in El Salvador, where the nearest streams, and lagunas at 27 of 154 survey sites, water or saturated soils were an estimated 400± including 26% of occupied sites (Table 1). We 600 m from the sites. However, although water also noted evidence of agrochemical contami- was not present during our January surveys (Fig. nation of waterways. In Costa Rica, major irri- 5), the sites were ¯ooded from September gation canals through the extensive sugar, rice, through November when ¯ycatchers ®rst arrive. and oil palm plantations at Bebedero, Canas, and Similar dramatic seasonal change occurs Coto 44 were marked with signs that read, ``No throughout the Paci®c lowlands. Flycatchers ar- SwimmingÐContaminated.'' rive during the invierno, when many occupied In El Salvador, only two survey locations sites are inundated by up to 6 m of water. By were within protected areas: Bosque Nancuchin- January and February, the verano is underway ame and Laguna El Jocotal. Although La Barra and local water levels are much reduced so that de Santiago in El Salvador is also a nationally some retain only limited surface water and/or protected area, all occupied Willow Flycatcher saturated soils. The fact that water is present at habitat was found outside of the borders. In Cos- all sites when ¯ycatchers arrive suggests it is an ta Rica, we did not detect Willow Flycatchers at important factor in winter habitat selection. Ko- the two survey locations within National Park ronkiewicz and Sogge (2000) found that ¯y- boundaries, but ¯ycatchers were found at local- catchers remained at wintering sites even after ly-protected sites at Bolson, Santa Cruz, and So- sites had dried substantially, and that the distri- limar. None of our Panama survey locations bution of ¯ycatchers within sites remained con- were located within protected areas. stant despite major changes in the distribution and amount of wet areas. DISCUSSION The tree and shrub components of Willow Because Willow Flycatcher subspecies are Flycatcher winter habitat varied in relative pro- distinguished by slight morphological and color portion among sites. Patches and/or stringers of differences (Unitt 1987), we could not con®- trees varied in size and shape, and the shrub dently differentiate among subspecies during our component at occupied sites ranged from dense ®eld surveys. However, because Unitt (1997) to sparse and/or scattered. At many sites, espe- examined 578 museum specimens of ``Traill's cially those in Costa Rica, Mimosa sp. formed Flycatcher'' taken during migration or in winter dense impenetrable thickets, whereas other sites and found no geographical segregation among in Panama and El Salvador contained very few wintering E. traillii subspecies, we believe that shrubs. Flycatchers foraged and roosted among our data apply to all subspecies, including E. t. dense shrubs at some sites (T. Koronkiewicz, extimus. Ecological segregation, such as might pers. obs.), and sang and foraged from exposed occur if different subspecies use different habi- perches along tree lines and forest and woodland tats within the local landscape, could mean that edges. As on the breeding grounds (Sedgwick our results are not equally applicable to all sub- and Knopf 1992), trees may provide ¯ycatchers species. Although such ecological segregation exposed perches from which to forage, and de- has not been demonstrated to date, it is worthy fend and view their habitat. Open areas, also re- of additional consideration and research. ported as a component of many Southwestern Willow Flycatcher breeding habitats (Sogge and HABITAT Marshall 2000, Allison et al. this volume), may Our habitat descriptions, although qualitative provide aerial foraging space. in nature, identi®ed what appear to be key com- ponents of wintering Willow Flycatcher habitat. SURVEY TECHNIQUE AND EFFORT Despite differences in overall size, shape, and Wintering Willow Flycatchers' response to plant species composition, Willow Flycatcher tape-playback was similar to that described for wintering sites consistently included standing or breeding ¯ycatchers (Sogge et al. 1997a). Be- slow moving freshwater (or saturated soils), cause eliciting song is useful in verifying species woody shrubs, patches and/or stringer of trees, identi®cation, and because many ¯ycatchers and open areas (Fig. 2). These components also were not detected until after the survey tape was characterize many ¯ycatcher breeding habitats, played, we consider tape-playback surveys (in- especially in the southwestern U.S. (Sogge and cluding the use of multiple calls and songs) to Marshall 2000). be a critical tool for effectively locating Willow Occupied wintering Willow Flycatcher habitat Flycatchers on the wintering grounds. 46 STUDIES IN AVIAN BIOLOGY NO. 26

FIGURE 3. Occupied Willow Flycatcher winter habitat along the Rio Corozal in Puerto Jimenez, Costa Rica. All of the Willow Flycatcher habitat was removed and converted to short grass pasture during the course of our surveys in 1999. The bulldozer can be seen at the center of the photo.

It was not our goal to conduct complete cen- ama (0.8 ¯ycatchers/survey hr) than we had pre- suses of Willow Flycatchers at our sites, and our viously done in Costa Rica (0.5 ¯ycatchers/sur- results do not re¯ect actual ¯ycatcher abun- vey hr). Thus, differences in the numbers of ¯y- dance. Over the course of our work, we altered catchers and/or rates of ¯ycatcher detections our survey methods based on initial results to (Appendix) in each country cannot be used as increase survey ef®ciency. During 1998 and an index of actual abundance or density. 1999, our Costa Rica surveys were conducted in The lack of historical records and recent re- a wide variety of habitat types, many of which ports for wintering Willow Flycatchers at high did not support wintering ¯ycatchers. In con- elevation suggested that elevation may limit ¯y- trast, we focused our 2000 surveys in El Sal- catcher distribution; thus, almost all (152 of 154) vador and Panama on habitat types in which we of our survey sites were located below 250 m. found wintering ¯ycatchers during the previous However, in January of 2001, ®ve Willow Fly- two years in Costa Rica. In El Salvador and Pan- catchers were recorded spontaneously singing at ama, we also enlisted the assistance of local or- approximately 430 m near Lago de GuÈija, El nithologists who provided valuable logistical in- Salvador (W. RodrõÂguez, pers. comm.), suggest- ing that additional surveys covering a wider formation and identi®ed areas most likely to range of elevations are warranted. contain suitable ¯ycatcher habitat. This more fo- cused approach and additional survey experi- CATTLE GRAZING AND AGRICULTURAL ACTIVITIES ence allowed us to survey more effectively in Historically, cattle ranching along the Paci®c El Salvador (5.4 ¯ycatchers/survey hr) and Pan- lowlands promoted the establishment and

TABLE 1. THE NUMBER OF SITES AT WHICH DIFFERENT TYPES OF HUMAN IMPACTS WERE NOTED DURING WILLOW FLYCATCHER WINTER SURVEYS IN 1998±2000

Type of human impact Cattle Trash and grazing Agriculture pollutants Occupied sites El Salvador (N ϭ 25) 24 16 18 Costa Rica (N ϭ 41) 40 11 1 Panama (N ϭ 11) 7 3 1 Total (N ϭ 77) 71 30 20 Unoccupied sites El Salvador (N ϭ 3) 2 2 0 Costa Rica (N ϭ 59) 46 28 4 Panama (N ϭ 15) 8 9 3 Total (N ϭ 77) 56 39 7 WILLOW FLYCATCHER WINTER HABITATÐLynn et al. 47

FIGURE 4. Willow Flycatcher winter habitat along Quebrada Pese, Panama. Sugar cane plantations surround the gallery forest and woodland. growth of permanent towns and villages and preclude presence of ¯ycatchers. However, cattle conversion of native habitats to pasture land. ranching can cause major impacts to Willow This conversion from wooded areas to pasture Flycatcher habitat. The most extensive habitat has been one of the most signi®cant changes in impacts occur from the practice of clearing en- land use throughout Latin America (Hartshorn tire areas of shrubs and trees to create open pas- 1992, Kaimowitz 1996); overall, from 1981 to tures. These intensively cleared pastures are 1990, more than 75 million ha of forested land maintained by removing woody vegetation, ren- were converted to cattle pastures (Houghton et dering the site unsuitable for wintering Willow al. 1991). We found ¯ycatchers using grazed ar- Flycatchers. Although grazing may have created eas that still contained scattered woody vegeta- Willow Flycatcher habitat by opening up areas tion; thus, the presence of cattle itself did not in otherwise dense forests, lands intensively

FIGURE 5. Willow Flycatcher habitat at Laguna El Jocotal, El Salvador. Site was approximately 400 m from water at the time of surveys, but contained standing water from September through November. 48 STUDIES IN AVIAN BIOLOGY NO. 26 managed for cattle pasture do not preserve or THE ROLE OF PROTECTED AREAS provide Willow Flycatcher winter habitat. Neotropical migrants require suitable sites in Large-scale permanent agriculture has also which to over-winter, and protection of winter- been encroaching on wetland habitats in Central ing habitat is one method to help ensure their America since the 1500s (Browning 1971), with conservation. However, conservation of natural modern agricultural practices playing a major resources and the establishment of national role in the conversion of wetlands and wood- parks and preserves face many obstacles in Cen- lands, and the degradation and contamination of tral America, including government and inter- lowland areas (Murray 1994, Biesanz et al. national funding constraints, lack of environ- 1999). Streams and rivers were diverted for ir- mental education, and high demands on remain- rigation, and in many areas, fertile wetlands ing natural resources. Furthermore, most pro- were drained completely to make way for large- tected areas are located in high elevation cloud scale plantations and export crops such as cot- forests, lowland rainforests, tidal and salt-water ton, rice, and African oil palm. As a result, marshes, and coastal mangroves; thus, they do freshwater wetlands are increasingly scarce not include suitable Willow Flycatcher winter along the Paci®c slopes of Central America. habitat. As of 2000, 14 of 24 Central American Like intensive cattle grazing, most agricultural Ramsar sites (wetlands of international impor- ®elds are cleared of trees and shrubs, rendering tance) were located in El Salvador, Costa Rica, them unsuitable as Willow Flycatcher habitat. and Panama (totaling 425,366 ha); only seven The few remaining trees (usually only one or (one in El Salvador, four in Costa Rica, and two two individuals wide) at these ®elds are gener- in Panama) contain freshwater lagunas or sea- ally planted along property lines and fence lines, sonally inundated ¯oodplains (Ramsar List or are remnant of the riparian forest once found 2001) with potential for suitable Willow Fly- along quebradas bordering the ®elds. Without catcher habitat. There may be a perception that the other key components of ¯ycatcher habitat the freshwater wetland areas that persist in Pa- nearby, such strips of trees do not comprise suit- ci®c lowland agricultural areas are so heavily able ¯ycatcher habitat. impacted that they are of low habitat value and Our cursory examination revealed a high po- not deserving of conservation attention or funds; tential for agrochemical impacts at some sites in this is certainly not the case for the wetlands that support wintering Willow Flycatchers. El Salvador (Laguna de Olomega, Laguna El Jo- Despite administrative protection, deforesta- cotal, Laguna San Juan, and Barra de Santiago) tion and contamination continue to plague ex- and Costa Rica (Bebedero, Canas, and Coto 44), isting protected areas occupied by Willow Fly- where vegetable crops and sugar cane ®elds are catchers. One example is Laguna El Jocotal in in close proximity to shorelines, riverbanks, and El Salvador, which was designated a nationally major irrigation canals. Agrochemicals are wide- protected area in 1996, and is the country's only ly used on crops throughout Central America; Ramsar site (Ramsar List 2001). In 2000, the El however, their effects on the surrounding envi- Salvador Ministry of Environment and Natural ronments and ultimately their effects on Neo- Resources acknowledged contamination and tropical migrants have not been well studied. over-®shing at El Jocotal (Joma 2000); local These pesticides and herbicides leach into rivers park personnel now patrol the laguna, but reg- and streams and/or enter the water directly as ulations are rarely enforced. During our surveys, run-off. Although organochlorides such as DDT cattle were seen grazing the shorelines and in are rarely used in Costa Rica, Panama, and El shallow waters. Local residents use the laguna Salvador, other highly toxic pesticides and her- to wash laundry with harsh detergents, and plas- bicides are common. Many chemicals, though tic containers from bleach and other products less persistent than organochlorides, can accu- were seen along the shoreline. Despite such mulate to toxic levels in birds, decrease local challenges, the protection of wetlands and as- faunal diversity, and cause declines in insect sociated habitat, even with minimal regulation, populations (Eisler 1985b, Hooper et al. 1990, may be an important step for preserving the Wil- Iolster and Krapovickas 1999). If overwintering low Flycatcher. habitat suitability for insectivorous migrants, such as the Willow Flycatcher, is related to in- RECOMMENDATIONS FOR FUTURE STUDIES sect availability, agrochemicals that reduce local The relative lack of observations and records insect populations may increase competition for of Willow Flycatchers on the wintering grounds food, increase foraging costs, and reduce fat re- is in part due to the dif®culties in positively serves and overall ®tness (Gard and Hooper identifying Empidonax species, and many gen- 1995). eral inventories, Christmas bird counts, and lists WILLOW FLYCATCHER WINTER HABITATÐLynn et al. 49 provided by birders and ornithologists identify tal contaminants in ¯ycatchers or their habitats, ¯ycatchers only to the genus Empidonax. In or- or to determine what effects such chemicals der to develop and prioritize conservation and might have on wintering ¯ycatchers. Given our management strategies for the Willow Flycatch- observations of contaminated waterways, and er, we need a better understanding of its distri- the nature and extent of the agricultural activities bution and ecology on the wintering grounds. that occur near wintering sites, detailed contam- Our study provides Willow Flycatcher distribu- inant studies are warranted. Chemical analysis tion data for some areas of El Salvador, Costa of water and/or soil samples at ¯ycatcher win- Rica, and Panama, but many unsurveyed areas tering sites could identify areas where contami- remain and may contain suitable habitat. Addi- nants pose a threat. Furthermore, as has been tional surveys are needed, particularly at the done on the breeding grounds (Mora et al. this northern and southern extents of the winter volume), chemical analysis of insects and sur- range and along a wider range of elevations. rogate bird species at wintering sites would help Quantitative habitat studies are needed to bet- determine if contaminants are likely accumulat- ter understand habitat requirements and to more ing at harmful levels within locally wintering precisely identify habitat availability on the win- ¯ycatchers. ter range. It would also be valuable to determine ACKNOWLEDGMENTS if remote-sensing data and GIS can be used to accurately identify areas of wintering habitat. Financial support for this project was provided by Research is needed to determine if distribution the U.S. Bureau of Reclamation, (Phoenix, AZ), U.S. Geological Survey, U.S. Fish and Wildlife Service and habitat use vary by sex and/or subspecies, (Region 2, Albuquerque, NM), and the U.S. Forest to document overwinter survivorship, and to Service. This work was made possible through collab- characterize the effects of seasonal water chang- oration with the Servicio de Parque Nacionales y Vida es on habitat selection. Studies are also needed Silvestre and the Universidad de El Salvador in El Sal- to determine if ¯ycatchers move, within and be- vador, the Organization for Tropical Studies in Costa tween sites, in response to seasonal changes in Rica, and the Smithsonian Tropical Research Institute the presence of surface water/saturated soil. On- in Panama. We thank P. Unitt and the San Diego Nat- going studies at relatively large ¯ycatcher sites ural History Museum for administrative support, as well as S. Leon and S. Sferra for their encouragement in Costa Rica (Koronkiewicz and Sogge 2000) and assistance with funding and contracts. Special suggest winter territoriality, and high return rates thanks go to the dedicated members of the ®eld crew: and site ®delity for wintering Willow Flycatch- E. Cohen, C. Drost, K. Enos, J. Hart, M. Halterman, ers. Comparative studies are needed to deter- P. Heavin, M. Johnson, S. Langridge, M. J. Mendez, mine if this is also true for smaller, more isolat- M. Santana, and S. Sferra. We thank G. Seutin and W. ed, and/or more fragmented winter habitats Rodriguez for their invaluable logistical and ®eld sup- throughout the ¯ycatcher's winter range. port during the 2000 surveys, and the numerous people Finally, quantitative data are needed to more who provided us with information on current wintering accurately assess the threat of land management locations, logistical advice, and assistance with permit applications. We are especially grateful to the many practices, particularly agrochemical use, to win- Central Americans who lent us their support and hos- tering Willow Flycatchers and their habitat. Our pitality during our surveys. This manuscript was great- survey project was not designed to detect the ly improved by the comments of O. Komar and an presence of agrochemicals or other environmen- anonymous reviewer. 50 STUDIES IN AVIAN BIOLOGY NO. 26

APPENDIX. WILLOW FLYCATCHER WINTER SURVEY EFFORT AND RESULTS FOR EL SALVADOR,COSTA RICA, AND PANAMA,JANUARY AND FEBRUARY 1998±2000

Number of Willow Number Fly- Flycatchers of sites Survey catchers per Country Survey location Year Coordinates surveyed hours detected survey hour El Salvador Rio Paz, Ahuachapan 2000 N 13Њ47.71Ј 1 1 4 4.00 W90Њ06.77Ј Rio Guayapa, Ahuachapan 2000 N 13Њ43.32Ј 1 1.1 24 21.82 W89Њ59.06Ј La Barra de Santiago, 2000 N 13Њ41.52Ј 1 8.4 35 4.17 Ahuachapan W89Њ56.58Ј Lago Coatepeque, Santa 2000 N 13Њ50.82Ј 1 1.5 0 0.00 Ana W89Њ34.18Ј Colima, Cuscatlan 2000 N 14Њ02.75Ј 2 3.4 10 2.94 W89Њ07.39Ј Suchitoto, Cuscatlan 2000 N 13Њ58.34Ј 2 7.0 13 1.86 W89Њ01.54Ј Bosque Nancuchiname, 2000 N 13Њ20.48Ј 1 2 30 15.00 Usulutan W88Њ43.14Ј Laguna de Olomega, San 2000 N 13Њ19.94Ј 11 11.9 30 2.52 Miguel W88Њ01.18Ј Laguna de San Juan, San 2000 N 13Њ22.08Ј 1 2.6 35 13.46 Miguel W88Њ09.58Ј Laguna El Jocotal, San 2000 N 13Њ19.15Ј 7 11.9 93 7.82 Miguel W88Њ14.59Ј El Salvador total 28 50.8 274 Costa Rica Parque Nacional Santa 1999 N 10Њ51.10Ј 5 21.5 0 0.00 Rosa, Guanacaste W85Њ36.88Ј Bebedero, Guanacaste 1998 N 10Њ21.12Ј 4 24.5 1 0.04 W85Њ10.50Ј Canas, Guanacaste 1999 N 10Њ21.21Ј 2 13.8 0 0.00 W85Њ5.96Ј Tempate, Guanacaste 1999 N 10Њ22.10Ј 4 23.2 1 0.04 W85Њ43.18Ј Parque Nacional Palo 1999 N 10Њ20.90Ј 5 22.4 0 0.00 Verde, Guanacaste W85Њ16.92Ј Bolson, Guanacaste 1999 N 10Њ21.31Ј 5 43.4 26 0.60 W85Њ25.17Ј Puerto Humo, Guanacaste 1999 N 10Њ17.97Ј 2 12.8 1 0.08 W85Њ24.98Ј Santa Cruz, Guanacaste 1999 N 10Њ19.74Ј 5 34.6 26 0.75 W85Њ38.97Ј Solimar, Guanacaste 1999 N 10Њ16.54Ј 5 21.5 54 2.51 W85Њ8.80Ј Hojancha, Guanacaste 1998 N 10Њ6.30Ј 3 8.6 0 0.00 W85Њ22.01Ј Punta Piedra, Guanacaste 1998 N 9Њ42.57Ј 3 9.1 0 0.00 W85Њ1.00Ј , 1999 N 10Њ4.16Ј 4 23.0 28 1.22 W84Њ53.96Ј Boca de Barranca, Puntar- 1999 N 9Њ53.42Ј 4 15.0 9 0.60 enas W84Њ40.75Ј Tarcoles/Agujas, Puntaren- 1999 N 9Њ51.05Ј 6 18.3 3 0.16 as W84Њ33.90Ј Punta Coyote, Caletas 1999 N 9Њ45.59Ј 4 9.8 8 0 W85Њ16.07Ј Rio Palo Seco, Puntarenas 1999 N 9Њ34.35Ј 8 26.6 26 0.98 W84Њ18.70Ј , Puntarenas 1999 N 9Њ6.65Ј 13 28.7 0 0.00 W83Њ20.46Ј WILLOW FLYCATCHER WINTER HABITATÐLynn et al. 51

APPENDIX. CONTINUED.

Number of Willow Number Fly- Flycatchers of sites Survey catchers per Country Survey location Year Coordinates surveyed hours detected survey hour San Vito, Puntarenas 1999 N 8Њ49.65Ј 3 5.8 0 0.00 W82Њ57.04Ј Coto Colorado/44, Puntar- 1999 N 8Њ33.72Ј 8 32.4 10 0.31 enas W82Њ57.47Ј Puerto Jimenez, Puntaren- 1999 N 8Њ30.93Ј 7 33.5 9 0.29 as W83Њ17.65Ј Costa Rica total 100 428.5 202 Panama Road to Almirante, Bocas 2000 N 9Њ00.24Ј 2 2.8 0 0.00 del Toro W82Њ15.99Ј RõÂo Guabo, Bocas de Toro 2000 N 8Њ56.99Ј 2 2 0 0.00 W82Њ11.29Ј San Felix/Las Lajas, Chiri- 2000 N 8Њ10.61Ј 3 5.6 7 1.25 qui W81Њ51.63Ј Paris, Herrera 1999 N 8Њ6.18Ј 3 13.0 0 0.00 W80Њ34.01Ј Pese, Herrera 2000 N 7Њ53.20Ј 1 4.8 14 2.92 W80Њ32.43Ј Tonosi, Los Santos 2000 N 7Њ26.85Ј 3 19.7 18 0.91 W80Њ22.32Ј Tocumen Marsh, Panama 2000 N 9Њ04.09Ј 2 10.9 8 0.73 W79Њ22.43Ј Gamboa, Panama 2000 N 9Њ07.24Ј 2 5.1 3 0.59 W79Њ43.61Ј Boca de Pacora, Panama 2000 N 9Њ02.30Ј 2 2.5 0 0.00 W79Њ18.17Ј Lago Alajuela, Colon 2000 N 9Њ11.40Ј 2 2.3 0 0.00 W79Њ33.97Ј Portobelo, Colon 2000 N 9Њ33.95Ј 1 2 4 2.00 W79Њ34.58Ј El Real, Darien 2000 N 8Њ06.40Ј 3 11.3 12 1.06 W77Њ43.98Ј Panama total 26 82.0 66