The Gray Flycatcher is a common inhabitant of arid woodland and shrublands of the interior western United States in summer and northern Mexico in winter. From sagebrush (Artemisia) to piñon-juniper (Pinus edulis ¿ Juniperus sp.) woodland to ponderosa pine (Pinus ponderosa) forests of the Great Basin and intermountain region, this flycatcher actively defends territories and forages for insects from shrubs or from branches low in trees. It often nests on top of large branches against the trunk of yellow pine, in forks of branches of piñon pine or juniper, or hidden within shrubs. Females lay clutches of 3 to 4 eggs in late May to early June, second clutches as late as July. Incubation lasts 14 to 15 days. Young fledge in about 16 days and are often fed by parents out of the nest for an additional 14 days. Individuals begin fall migration in August and undergo complete feather molt on the wintering grounds. Although the diet and foraging behavior of this species have not been studied in detail, observed foraging behaviors include picking insects off the ground from a perch or in flight, as well as conventional flycatcher behavior of sallying to catch flying insects or hovering to pluck insects off vegetation.
The close similarity of the Gray Flycatcher to the Dusky Flycatcher (Empidonax oberholseri) has led to taxonomic confusion and subsequent name changes for both species. These problems were finally resolved by Allan R. Phillips (1939) when he discovered that the type specimen designated for the Dusky Flycatcher was in fact a Gray Flycatcher. Even after the Gray Flycatcher was recognized as a separate species in 1889, many studies did not accurately discriminate between Dusky and Gray flycatchers, sometimes including reports that were a composite of both. It was Allan Phillips again who provided a major breakthrough in identification that made the Gray Flycatcher perhaps the easiest species of Empidonax to identify in the field when he described its habit of wagging its tail in a gentle downward movement, similar to a slowed-down tail wag of a phoebe, rather than flicking the tail up and then down as performed by other Empidonax (Phillips 1944).
Because of difficulties in identification, early nomenclatural confusion, and this species' preference for remote haunts in sparsely populated areas, there is a dearth of ecological studies. Nevertheless, research in California and Utah (Russell and Woodbury 1941, Johnson 1963) has provided important information about the phenology, nesting behavior, parental behavior, vocalizations, and ecological relationships of this species with other western Empidonax flycatchers. Not until the early twentieth century was the Gray Flycatcher known to breed in the United States. Before then it was presumed to breed in northern Mexico and to wander northward in the fall. Improved characters for identification, such as the tail wag and others (e.g., see Whitney and Kaufman 1987), facilitated the discovery and documentation of Gray Flycatchers in the field and helped foster a more complete knowledge of the migration and breeding distribution of this species, including recent range expansions into central Washington and southern British Columbia (Yaich and Larrison 1973, Lavers 1975, Cannings 1987, Smith et al. 1997), and into southwestern California (Johnson and Garrett 1974).
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