Willow Flycatcher

The Willow Flycatcher (Empidonax traillii) is a small, insectivorous songbird belonging to the tyrant flycatcher family (Tyrannidae). It is a member of the notoriously difficult-to-identify Empidonax genus, often collectively referred to by birders as 'empids.' Historically, the Willow Flycatcher and the Alder Flycatcher were considered a single species called 'Traill's Flycatcher.' However, they were split in 1973 based primarily on their distinct vocalizations, subtle breeding habitat preferences, and lack of interbreeding. The Willow Flycatcher is a migratory species, breeding across much of the United States and southern Canada, and wintering in the Neotropics. While the species as a whole is relatively common, the Southwestern subspecies (E. t. extimus) is federally endangered in the United States due to the loss and degradation of its specialized riparian habitat.

Like other Empidonax flycatchers, the Willow Flycatcher has an upright posture and subtle, understated plumage. It is olive-brown to greenish-gray above, with a whitish or pale-yellow belly and a clean, white throat.

Key field marks include:

• Eye-ring: Extremely faint, thin, or entirely absent, which helps separate it from the bolder-eyed Least and Acadian Flycatchers.
• Wingbars: Two whitish to dull buffy wingbars on each wing.
• Bill: Relatively long, broad, and flat; the upper mandible is dark, while the lower mandible is almost entirely pale yellow-orange.
• Primary projection: Moderate to long, which can help differentiate it from shorter-winged species.

Similar Species: The Alder Flycatcher (Empidonax alnorum) is virtually identical in appearance. Visually separating them in the field is rarely possible with 100% certainty, though the Willow Flycatcher tends to have a slightly greener back, a less distinct eye-ring, and a slightly larger bill with a fully pale lower mandible. Identifying them reliably depends on hearing their vocalizations.

During the breeding season, the Willow Flycatcher is highly tied to moist, shrubby habitats. Typical breeding grounds include:

• Riparian corridors lined with willows, alders, and buttonbush.
• Wet, brushy meadows, mountain shrublands, and swamp edges.
• For the Southwestern subspecies, dense streamside vegetation near slow-moving water.

Its breeding range spans from southern British Columbia across southern Canada to the northeastern US, and south throughout much of the western and central United States. In late summer, these flycatchers migrate southward. They winter in open or semi-open wet habitats, second-growth forests, and shrubby areas from southern Mexico down through Central America to northwestern South America.

Vocalizations: Vocalizations are the primary key to identifying this species. Its song is a dry, buzzy, two-syllabled sound often transcribed as 'fitz-bew' or 'FITZ-bew,' with the accent heavily placed on the first syllable. Its typical call note is a dry, sharp, metallic 'whit' or 'pit.'

Foraging & Feeding: The Willow Flycatcher is an active visual hunter. It typically perches upright on an exposed, low-to-mid-level twig in a shrub, waiting for insect prey. When it spots an insect, it sallies out into the air to snap it up in flight (hawking) or hovers briefly to pluck it from leaves, twigs, or the ground (gleaning), before returning to the same or a nearby perch.

Nesting: Females build a neat, open-cup nest constructed of grass, fibers, and bark shreds, lined with finer grasses or feathers. The nest is typically nestled in a vertical fork of a deciduous shrub or small tree, usually within 1 to 3 meters of the ground. Clutch size is typically 3 to 4 creamy-white eggs, incubated for around 12 to 15 days.