Birds
Willow Flycatcher
Empidonax traillii · also called willow flycatchers
Two flycatchers perch in nearly identical willow thickets, looking so alike that only their completely different songs give away which is the willow flycatcher and which is its close relative, the alder flycatcher.
Overview
The willow flycatcher, Empidonax traillii, is a small, insect-hunting bird native to riparian willow and shrub thicket habitat across much of North America. Its near-total visual resemblance to a sibling species, reliance on song for identification, and the federally endangered status of its southwestern subspecies make it one of the more genuinely tricky and conservation-relevant flycatchers in North America.
Told apart only by ear
Look at a willow flycatcher and an alder flycatcher side by side and even experienced birders often can’t tell them apart, leaving song as the one dependable clue separating these two closely related species.
Status
Least Concern overall but decreasing, with the southwestern subspecies federally listed as endangered due to severe riparian habitat loss and cowbird parasitism.
Willow Flycatcher: common questions
How can you tell a willow flycatcher from an alder flycatcher?
The two species look almost indistinguishable by sight, so the most reliable way to tell them apart is by song, since the willow flycatcher produces a sharp, buzzy "fitz-bew" while the alder flycatcher's call sounds more like "free-beer," a difference the birds themselves rely on to recognise their own species.
Why is the southwestern willow flycatcher federally endangered?
This subspecies has lost much of the dense riparian willow thicket habitat it depends on for nesting to development, livestock grazing, and the spread of invasive plant species along southwestern rivers, and it also faces significant pressure from brood parasitism by brown-headed cowbirds.
What does a cowbird do to a willow flycatcher's nest?
A brown-headed cowbird will lay its own egg directly in a willow flycatcher's nest, and the flycatcher often ends up raising the cowbird chick, sometimes at the direct cost of its own young, a form of brood parasitism that adds significant pressure to already vulnerable populations.
Where does the willow flycatcher prefer to nest?
This species nests almost exclusively in dense willow and shrub thickets near water, a specific habitat requirement that means suitable breeding sites can be genuinely limited, particularly in the arid Southwest where riparian habitat is scarce to begin with.