Alder Flycatcher

The Alder Flycatcher (Empidonax alnorum) is a small, migratory passerine belonging to the tyrant flycatcher family (Tyrannidae). It is a member of the notoriously difficult Empidonax genus, often collectively referred to by birders as "empids." For many decades, the Alder Flycatcher and the Willow Flycatcher (Empidonax traillii) were considered a single species called "Traill's Flycatcher." In 1973, the American Ornithologists' Union officially split them based on distinct differences in song, nesting habits, habitat preferences, and genetic markers. True to its name, this species is highly associated with wet, shrubby northern ecosystems where it can be heard calling from the dense foliage.

To the human eye, the Alder Flycatcher is visually identical to many other Empidonax flycatchers, particularly the Willow Flycatcher. Successful field identification almost always relies on hearing its voice.

Key Visual Features

• Plumage: Olive-green to brownish-olive upperparts and a pale throat. The chest is washed with olive-gray, while the belly has a subtle, pale yellow wash.
• Wings: Features two distinct whitish-to-buffy wingbars. The primary projection (how far the folded wingtips extend relative to the tail) is moderately long.
• Eye-ring: A narrow, whitish eye-ring is typically present but is often faint, thin, or incomplete.
• Bill: The bill is relatively large and broad-based, with a mostly orange or pale peach lower mandible and a dark upper mandible.

Distinguishing from Similar Species

• Willow Flycatcher: Visually indistinguishable. The Willow Flycatcher is on average slightly browner, has a less distinct eye-ring, and has a slightly shorter primary projection, but these traits overlap completely. Safe separation requires voice.
• Least Flycatcher: Smaller, with a much bolder, rounder white eye-ring, shorter bill, and shorter primary projection.
• Yellow-bellied Flycatcher: Has a bright yellow throat and a much greener back.

During the breeding season, the Alder Flycatcher occupies wet, shrubby, early-successional habitats.

• Breeding Habitat: Alder swamps, willow-lined streambanks, low bogs, muskeg, and damp brushy marshes. They are also found in wet, overgrown abandoned fields and regenerating clearcuts in northern climates.
• Geographic Range: Their breeding range stretches across Alaska, Canada (from the Yukon to the Atlantic provinces), and the northeastern United States down into the Appalachian Mountains.
• Migration: A long-distance migrant, the Alder Flycatcher departs its northern breeding grounds early in late summer (August) and journeys to South America. It winters primarily in the western Amazon basin and the eastern slopes of the Andes, utilizing tropical shrubby edges, second-growth forests, and riverbanks.

Foraging and Diet

Like other tyrant flycatchers, the Alder Flycatcher feeds primarily by "hawking"—perching conspicuously on an outer twig, darting out to snatch an insect in mid-air, and then returning to the same or a nearby perch. It also gleans insects directly from leaves and twigs. Its diet consists almost entirely of insects, including beetles, wasps, bees, flies, caterpillars, and winged ants. During migration and on its wintering grounds, it may occasionally consume small berries.

Voice

Voice is the single most important tool for identifying this species in the field.

• Song: A buzzy, three-syllabled phrase, classically written as "fee-bee-o" or "free-beer-o", with the heaviest accent placed on the second syllable and a downward slide on the third.
• Call: A sharp, flat "pip" or "peek" call, which is distinctly different from the soft, liquid "whit" call of the Willow Flycatcher.

Nesting and Breeding

The nesting site is usually located low in a deciduous shrub or sapling (often an alder, willow, or dogwood), typically less than 2 meters (6 feet) off the ground. The nest is a bulky, loosely constructed cup of dried grass, plant fibers, and bark strips, lined with finer grasses. Unlike the neat nest of the Willow Flycatcher, the Alder's nest is often described as untidy, frequently featuring dangling pieces of grass hanging from the bottom. The female lays 3 to 4 creamy-white eggs marked with brown spots, which she incubates for about 12 to 14 days.