Empidonax traillii
The Willow Flycatcher illustrates several problems for Texas atlasers . The first is sorting out migrants from possible breeders. Migrant bird species do not pass through like convoys of ships. Rather a few come early and some are laggards who may never reach their destination in tine to breed.
Texas straddles the biogeographical area where the ranges of eastern and western bird species meet or overlap. This gives Texas a large bird list but also the possibility of local extirpation.
Another problem is taxonomic change, lumping or splitting. The Willow and Alder (Empidonax alnorum) flycatchers were once considered subspecies of Trail’s Flycatcher. Fortunately the split occurred before the atlas fieldwork, but identification of these two, visually identical species can still be a problem.
DISTRIBUTION. During the 1987-1992 field work of the TBBA project, observers found only 2 possible records in the High Plains of the northern Panhandle for Willow Flycatcher. Lockwood and Freeman (2004) report the last nesting of Willow Flycatcher in Texas occurred in Brewster County in the 1890’s; prior to then the species had been a summer resident of the central and western parts of the Trans Pecos region.
In migration Willow Flycatcher is uncommon to rare throughout the state, although less common than Alder Flycatcher in the eastern half of Texas. The former nesting population in Trans Pecos Texas was probably part of the endangered Southwestern Willow Flycatcher, referred to by Oberholser (1974) as Little Trail’s Flycatcher.
Willow Flycatcher breeds from southwestern Canada through Washington and Oregon, spots in California and the Rocky Mountains and the Colorado Plateau to Arizona and New Mexico. East of the Great Plains the range extends from southern Manitoba southeast through the Great Lakes states to southern Ontario and Quebec and south to Missouri, Tennessee, Virginia, and the northeastern states (Sedgwick 2000).
In winter without vocal clues “Trail’s” Flycatcher is found from the coast of Oaxaca (Mexico) south along the Pacific shore to Panama and on the Atlantic shore from Honduras to Costa Rica. It also winters in South America erst of the Andes to northwest Argentina (Sedgwick 20000).
SEASONAL OCCURRENCE. North-bound Willow Flycatchers move through Texas from very late April to early June. South-bound migrants move through from late July to early October. (Oberholser 1974, Lockwood and Freeman 2004). Breeding in Texas probably occurred in June and July (Sedgwick 2000).
BREEDING HABITAT. In Arizona Southwestern Willow Flycatcher breeds in cottonwood-willow and saltcedar-Russian olive habitats (McCarthey 2005).
The nest is placed in a fork of or on a horizontal limb of a shrub, 1-4.5 m (3-15 ft) above ground. Usually a compact cup of plant bark and fiber and grass; lined with a thin layer of fine grasses and silky plant materials, giving the nest a silvery appearance from above. The nest typically has feathers in the rim and may have plant material dangling from the bottom. It is similar to that of Yellow Warbler (Dendroica petechia; Harrison 1979).
The female lays 3-4 creamy white to buffy , smooth, dull or slightly glossy eggs (see Harrison [1979] for photo of markings). She incubates them for 12-15 days. The nestling period is 14-15 days; the young then often huddle together on a perch for 3-4 days, then follow adults until 24-25 days old. Parasitism by Brown-headed Cowbird (Molothrus ater) is much higher in the western United States than in the east (Harrison 1979, Sedgwick 2000).
STATUS. The subspecies E t. extimus which formerly bred in the Trans Pecos and Edwards Plateau regions of Texas is now listed as Endangered by the U. S. Fish and Wildlife Service. (Oberholser 1974, Sedgwick 2000, Lockwood and Freeman 2004).
North American Breeding Bird Survey data from the 1788 40 km (25 mi) routes on which this species was detected in the United States and Canada produced a 95% confidence interval (There is a 95% chance that the actual population trend will be between these two numbers.) of -0.6 to +0.2% population change per year for the period 1966-2004 (Sauer et al. 2005). These values suggest populations of Willow Flycatchers of the non-endangered subspecies are in relatively good shape and migrant Willow Flycatchers should continue to be present in Texas for the foreseeable future.
Text by Robert C. Tweit (2006)
Literature cited.
Harrison, H. H. 1979. A field guide to western birds’ nests. Houghton Mifflin, Boston, MA.
Lockwood, M. W. and B. Freeman. 2004. The TOS handbook of Texas birds. Texas A&M University Press, College Station
McCarthey, T. 2005. Willow Flycatcher (Empidonax traillii). In Arizona breeding bird atlas pp. 302-303 (T. (T. E. Corman and C. Wise-Gervais, eds.) University of New Mexico Press, Albuquerque
Oberholser, H. C. 1974. The bird life of Texas. University of Texas Press, Austin.
Sauer, J. R., J. E. Hines, and J. Fallon. 2005. The North American Breeding Bird Survey, results and analysis 1966-2004. Version 2005.1. USGS Patuxent Wildlife Research Center, Laurel MD (Web site, http://www.mbr-pwrc.usgs.gov/bbs).
Sedgwick, J. A. 2000. Willow Flycatcher (Empidonax traillii). In The birds of North America, No. 533 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.