Another inhabitant of the Trans-Pecos mountains, the Olive-sided Flycatcher is often seen perched at the top of a tall tree. Its loud quick-THREE BEERS! song confirms the identification.
From the Olive-sided Flycatcher’s elevated perch, it sallies out to catch flying insects in mid-air, a behavior typical of pewees. This species can also be distinguished from other pewees by its characteristic perch at the top of the tree, Western Wood-Pewees (Contopus sordidulus) forage from the ends of lower branches.
The aggressive territorial defense by both members of an Olive-sided Flycatcher pair (a territory may be as large as 40-45 ha [100-113 acres]), probably reduces nest predation (Altman and Sallabanks 2000).
DISTRIBUTION. During the 1987-1992 field work for the TBBA project, observers found possible or probable breeding evidence for Olive-sided Flycatcher in and near the Davis and Guadalupe mountains of Trans-Pecos Texas. Lockwood and Freeman (2004) describe the species as an uncommon summer resident at upper elevations in the Guadalupes and rare and irregular in the Davis Mountains in summer.
The possible reports in latilong blocks 29096 and 27098 probably represent late migrants as the habitat in these areas is not appropriate and they are well outside the usual breeding range.
Outside Texas the species breeds across North America from Alaska to Newfoundland. In the east the breeding range extends south to northern portions of Minnesota, Wisconsin and Michigan, the Adirondack and Catskill mountains of New York and western Massachusetts. In the west breeding occurs south through the Cascades, Sierras and Rocky Mountains and the California Coast Range to northern Baja California, the Mogollon Rim in Arizona and Gila Mountains of New Mexico.
In fall Olive-sided Flycatchers migrate south to winter from southwest Mexico to Panama and the northern Andes and higher elevations of Venezuela and adjacent countries of South America (Altman and Sallabanks 2000).
SEASONAL OCCURRENCE.Olive-sided Flycatchers move north throughout Texas between about March 3 and June 15, most pass through between late April and early June. The peak of breeding probably occurs from late Nay to late July. Southbound migrants are present from July 4 to November 27 with most movement occurring from mid- August to late September.(Oberholser 1974, Altman and Sallabanks 2000, Lockwood and Freeman 2004).
BREEDING HABITAT. Most breeding probably occurs at elevations near 2400 m (8000 ft) in the Trans-Pecos mountains. Habitat around a nest site in the Guadalupe Mountains included ponderosa pine, Douglas fir and oaks (Oberholser 1974).
The nest is usually placed well out from the trunk of a coniferous tree on a horizontal branch, often in a clump of vertical twigs where it is concealed in needles. It is usually 2-15 m (7-50 ft) above ground and is a flat, saucer- shaped structure composed of twigs, rootlets, and lichens lined with pine needles, fine rootlets and mosses. The outside diameter is 12.5-15 cm (5-6 in0, height 5 cm (2 in), inside diam 6.5 cm (2.5 in) and cup depth 2.5 cm (1 in).
The female lays 3 eggs, rarely 2 or 4, smooth, lusterless, creamy white to light buff eggs(see Harrison  for photo of markings). She incubates them for 10-17 days. The nestling period has not been determined accurately because young birds remain near the nest after leaving. Olive-sided flycatcher is a rare host for Brown-headed Cowbird. The species raises only one brood per season, but may renest at least twice after nest failure in the incubation stage (Oberholser 1974, Harrison 1979, Altman and Sallabanks 2000).
STATUS. The status of Olive-sided Flycatcher as a breeding species in Texas is tenuous at best. The North American Breeding Bird Survey (BBS) does not sample this species in Texas, probably a consequence of its rarity in the Davis Mountains and lack of access by road to habitat in the Guadalupe Mountains. Across North America data from 789 BBS routes produced a statistically significant trend of -3.5% population change per year for the period 1966-2004 (Sauer et al. 2005). This population trend and its listing as a Species of Special Concern by the United States Fish and Wildlife Service (Altman and Sallabanks 2000) suggests that its current status as an uncommon to rare migrant through Texas (Lockwood and Freeman 2004) may shift to rare in the future.
Text by Robert C. Tweit (2005)
Altman, B. and R. Sallabanks. 2000. Olive=sided Flycatcher (Contopus cooperi). InThe birds of North America, No. 502 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
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.
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).