Swainson's Thrush

Swainson's Thrush is a widespread breeder across boreal and montane forests of North America, best known to many birders as a common but often invisible migrant, detected mainly by its distinctive nighttime flight calls as huge numbers pass overhead each spring and fall. It is an olive-brown to warm brown thrush with a buffy wash across the face and a bold buffy eyering.

Two main plumage forms exist: a grayer, olive-backed form breeding across most of the continent, and a warmer, russet-backed form along the Pacific coast, though both share the same buffy facial pattern that helps distinguish the species from its Catharus relatives.

Key field marks

• Buffy eyering and buffy wash on the lores and face
• Olive-brown to warm russet-brown upperparts (varies geographically)
• Spotted upper breast on a buffy background
• No strong contrast between tail and back (unlike Hermit Thrush)

Similar species

• Hermit Thrush: white (not buffy) eyering and a reddish tail that contrasts with the back.
• Gray-cheeked Thrush and Bicknell's Thrush: lack the warm buffy face and eyering, appearing colder gray overall with a faint, less distinct eyering.
• Veery: more uniformly tawny with much fainter spotting.

Habitat

Swainson's Thrushes breed in coniferous and mixed forests, including boreal spruce forest across Canada and Alaska, and moist coastal and montane forests in the Pacific Northwest and western mountains.

Range

The species breeds broadly across Canada, Alaska, the Pacific Northwest, and higher-elevation forests of the western United States and northern New England. It winters primarily in Central America and South America.

Migration

Swainson's Thrush is a long-distance, mostly nocturnal migrant, passing through the rest of the United States in huge numbers during spring and fall, often detected overhead at night by its distinctive short, whistled flight call.

Behavior

Swainson's Thrushes forage on or near the ground in forest understory, taking insects and other invertebrates, and shift toward fruit as an important food source during migration and winter.

Voice

The song is a series of flute-like notes that spiral upward in pitch, quite different from the downward-spiraling song of the Veery; the flight call, a short, liquid "whit" or "queep," is frequently heard from migrating flocks passing overhead at night.

Nesting

Nests are built low in shrubs or small trees, generally within a few meters of the ground, constructed as a compact cup of twigs, moss, and grass. Females lay 3-4 pale blue eggs, typically marked with brown spots.