Empidonax difficilis

Empidonax difficilis (including insulicola) and E. occidentalis were formerly (e.g., AOU 1998) considered separate species, although they had previously (e.g., AOU 1957, 1983) been considered conspecific (as Western Flycatcher). The two are again treated as a single species based on extensive hybridization and lack of consistent vocal, genomic, or morphological differentiation in a broad contact zone in southern British Columbia, southwestern Alberta, eastern Washington, Idaho, and Montana (Rush et al. 2009, Linck et al. 2019, Hopping 2022) (AOS 2023).

This species has a large range in western North America with a large population size, numerous subpopulations, and no evidence of threats or declines.

[difficilis group] Nesting range extends from southeastern Alaska and northwestern and central British Columbia (including Queen Charlotte and Vancouver islands) south to southwestern California (generally west of Cascades and Sierra Nevada) and mountains of northern and southern Baja California (AOU 1998, Lowther 2000). Range in southeastern British Columbia, Alberta, and north-central and northeastern Washington is uncertain and in need of further study. Winter range is mainly along Pacific coast lowlands of Mexico (0-1,500 meters elevation) from southern Baja California and northwestern Mexico (southern Sonora) south to Oaxaca west of the Isthmus of Tehuantepec, rarely north to California and Arizona (Howell and Webb,1995, AOU 1998, Lowther 2000) (AOS 2023).

[occidentalis group] Breeding range extends from southeastern Washington, southwestern Alberta, northern Idaho, western Montana, Wyoming, and western South Dakota south (generally east of Cascades and Sierra Nevada) to northern California, Nevada, and central and southeastern Arizona, and in Mexican highlands to Oaxaca (west of Isthmus of Tehuantepec), Puebla, and west-central Veracruz, and east to western Nebraska (rarely), central Colorado, central New Mexico, and western Texas (AOU 1989). Centers of abundance occur in Arizona, New Mexico, Colorado, central Utah, the Black Hills region of South Dakota, and northern Idaho (Sauer et al. 1997). The non-breeding range extends from southern Baja California, and northern Mexico (casually to central California and southern Arizona) south through breeding range, occurring also in lowland areas south to Isthmus of Tehuantepec; reports from Chiapas, Guatemala, and Honduras are based on E. flavescens (AOU 1989). Casual in migration in Tres Marias Islands (off Nayarit), eastern New Mexico, and southwestern Kansas (AOU 1989) (AOS 2023).

The insulicola group is resident in the Channel Islands off southern California (AOU 1989).

Casual to accidental [difficilis group] along the eastern seaboard from Nova Scotia (Sable Island) south to northcentral Florida. Accidental [occidentalis group] in southern Louisiana; reports from southeastern Texas are insufficiently documented. Numerous other records in eastern North America have not been satisfactorily identified to group.

This species is represented by a large number of occurrences (subpopulations).

Certainly habitat alteration is a threat to local populations, but overall this species faces no major threats. This species often nests on buildings and does not require pristine habitat.