The Southwestern Willow Flycatchers (Empidonax traillii extimus) is a small, endangered perching bird.
The Southwestern Willow Flycatcher measures about 5.75 inches (15 cm) in length and is roughly the size of a sparrow, weighing only about 0.4 ounces (12 g). Males and females look alike.
The plumage is greenish or brownish-grey above, with a white throat and a pale olive chest. The belly is pale yellow. It has two white wing bars.
The upper beak is dark, and the lower beak is light.
It closely resembles the other races of Willow Flycatcher, and several other species of the Empidonax genus, particularly the closely related Alder Flycatcher (Empidonax alnorum).
The Empidonax flycatchers are renowned as one of the most difficult groups of birds to distinguish by sight alone.
Subspecies and Ranges
- E.t. extimus (Southwestern Willow Flycatcher): Breeds in southern California (from the Santa Ynez River south), Arizona, New Mexico, extreme southern portions of Nevada and Utah, extreme southwest Colorado, and western Texas. Breeds in extreme northern Baja California del Norte and Sonora and possibly Mexico.
- E.t. adastus: Breeds from Colorado west of the plains to the west through the Intermountain/Great Basin states, and into the eastern portions of California, Washington, and Oregon.
- E.t. brewsteri: Breeds in central/coastal California north, through western Oregon and Washington to Vancouver Island.
- E.t. traillii: Breeds across the middle and northern United States and southern Canada, from New England and Nova Scotia west, through northern Wyoming and Montana, and into British Columbia.
- [E.t. campestris] – Unconfirmed subspecies. Breeds in the northern and western portions of E.t. traillii range.