Bicknell's Thrush

Bicknell's Thrush is one of North America's rarest and most range-restricted breeding songbirds, nesting almost exclusively in dense, stunted spruce-fir forest on mountaintops in the northeastern United States and adjacent Canada. It was only recognized as a species distinct from the Gray-cheeked Thrush in the early 1990s, and the two remain extremely difficult to tell apart in the field.

Compared to Gray-cheeked Thrush, Bicknell's is slightly smaller and shows warmer brown tones, with somewhat more contrast between a reddish-brown tail and the duller back, plus a hint of yellow at the base of the lower bill.

Key field marks

• Small, compact Catharus thrush
• Warm brown upperparts with a reddish-brown tail showing modest contrast with the back
• Faint grayish eyering
• Yellowish base to the lower mandible (variable)

Similar species

• Gray-cheeked Thrush: essentially identical in the field; slightly larger, colder gray-brown with less tail-back contrast, and breeds in subarctic taiga rather than montane spruce forest. Voice and precise location/elevation are the most reliable clues.
• Swainson's Thrush: buffy face and eyering, unlike Bicknell's grayer face.

Habitat

Bicknell's Thrush is a habitat specialist of dense, stunted, high-elevation spruce-fir forest, generally found only above roughly 900 m (3,000 ft) on mountains, often in areas subject to fir waves and dense regenerating growth.

Range

The breeding range is tiny and fragmented, limited to mountaintops in the northeastern United States (White Mountains of New Hampshire, Green Mountains of Vermont, Adirondacks of New York, parts of Maine) and adjacent Quebec and the Maritime provinces of Canada. It winters almost entirely on a few Caribbean islands, especially Hispaniola.

Migration

Bicknell's Thrush is a medium-distance migrant, but its extremely narrow wintering range concentrated in Caribbean montane forest, combined with ongoing deforestation there, makes it especially vulnerable to habitat loss on both ends of its migration.

Behavior

Bicknell's Thrushes forage on and near the ground within dense montane forest, taking insects and other invertebrates along with fruit, and are notoriously secretive and difficult to observe well even where present.

Voice

The song is very similar to Gray-cheeked Thrush's thin, downward-spiraling phrases, but often described as slightly more variable and complex; the flight call also closely resembles that of Gray-cheeked Thrush, making voice alone an imperfect distinguishing tool.

Nesting

Nests are built low in dense spruce or fir saplings within the stunted montane forest, constructed as compact cups of twigs and moss. Females lay 3-4 pale blue eggs, and the species' restricted breeding and wintering habitats make it a species of significant conservation concern.