The Willow Flycatcher is a widespread and common summer resident in Oregon, known for its preference for shrubby, often wet habitats. Like other Empidonax flycatchers, they are notoriously difficult to identify by sight alone due to their similar, drab plumage. This is especially true when trying to distinguish between males and females.

In the case of Willow Flycatchers, male and female birds are virtually indistinguishable in their plumage. There are no reliable visual cues in their coloration or markings to tell them apart in the field.

General Characteristics (Both Sexes)
Size: A small to medium-sized flycatcher, around 5.5-6.5 inches (14-17 cm) long. They are generally smaller than Western Wood-Pewees.
Plumage:
Upperparts: Dull brownish-olive to gray-green on the back, head, and wings. The overall tone can vary slightly depending on subspecies and individual variation, but it's always muted.
Underparts: Whitish throat that often contrasts with a pale olive-gray wash across the breast and flanks. The belly is usually a pale yellowish or dull off-white.
Wingbars: They typically have two whitish or buffy wingbars, though these can be indistinct, especially on worn plumage.
Eye-ring: The eye-ring is usually very faint or absent, which is a key distinguishing feature from some other Empidonax species that have more prominent eye-rings.
Bill: A short, wide bill. The upper mandible (top part) is dark, while the lower mandible (bottom part) is typically entirely yellowish or pale pinkish-orange, often with a dark tip. This pale lower mandible is a good field mark.
Shape: Relatively flat-headed compared to some other flycatchers, and they have a fairly long bill.
Perching Behavior: They typically perch upright within dense shrubs and small trees, often near water. They sally out to catch insects in mid-air and return to a perch. They may also glean insects from foliage while hovering.
Vocalization: This is by far the most reliable way to identify Willow Flycatchers and distinguish them from other very similar Empidonax species (especially the Alder Flycatcher, which is virtually identical visually). Their song is a distinctive, sneezy, two-part phrase: "fitz-BEW!" (with the accent on the second syllable). They also have a short "whit" or "brit" call.

Male Willow Flycatcher in Oregon
Plumage: Indistinguishable from the female.
Size (Subtle): Males are, on average, very slightly larger than females, but this difference is not perceptible in the field.
Singing: Males are the primary singers of the "fitz-BEW!" song, using it to establish and defend their territory and attract a mate. You'll hear them singing frequently from prominent perches within their shrubby habitat during the breeding season.

Female Willow Flycatcher in Oregon
Plumage: Indistinguishable from the male.
Size (Subtle): Females are, on average, very slightly smaller than males.
Nesting: The female is responsible for building the nest, which is a neat, open cup made of plant fibers, grasses, and fine materials, often lined with softer items. It is typically placed in a vertical fork of a shrub or small tree, usually relatively low to the ground. She also does most or all of the incubation. Both parents feed the young.

Habitat in Oregon
In Oregon, Willow Flycatchers are strongly associated with riparian shrubland and other areas with dense, shrubby vegetation, often near water. This includes:
Willow thickets along streams, rivers, and ponds
Wet meadows with scattered shrubs
Swamps and marsh edges
Shrubby clearings and regenerating forests, especially in western Oregon
They are found from sea level along the coast and interior valleys to higher elevations west of the Cascades summit, and in various riparian zones in eastern Oregon.