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Bicknell's Thrush (Catharus bicknelli)
Distribution

Breeding: On high mountain peaks from southeastern Quebec, south to the Catskill Mountains of New York, across northern New England to Nova Scotia.Bicknell's Thrush breeding range

Winter: Greater Antilles; center of range is probably the Dominican Republic; specimens and sightings are known from the Dominican Republic, Haiti, Puerto Rico, Cuba, and St. Croix.


Breeding habitat

In New York and New England, found in sub-alpine forests (elevations >3,000 feet or 920 meters) usually dominated by balsam fir and red spruce. In Canada may breed in more varied habitats such as stunted montane coniferous, mixed second-growth, and dense coastal spruce forests.

Conservation status

The Bicknell's Thrush is of very high importance because of its extremely limited range, small overall population, and its extreme vulnerability to deforestation in its limited winter range. Identifying large and stable populations of this species, as well as determining its precise habitat and area requirements, especially sensitivity to silvicultural practices and other disturbances, will be important for conserving populations.

Description

Male: Upperparts olive-brown with a slightly more reddish tail and primaries, indistinct eye-ring. Underparts are white with bold dark spots on the breast and a slight yellow tinge. Flanks are brownish-gray. Gray-cheeked Thrush is very similar to the Bicknell's, but has more olive on both the back and tail. Bicknell's is also slightly smaller than the Gray-cheeked Thrush, especially when comparing wing length. Separation of these two species away from the known breeding range may be impossible.

Female: Same as male.

Juvenile: Buffy-brown speckled plumage.

Vocalizations

Song: The Bicknell's song is very similar to the song of the Gray-cheeked Thrush. It consists of a jumbled series of notes with a final trilled note that is higher than the preceding notes. At the end of the Gray-cheeked Thrush's song the final trilled note is slurred downward.

Calls: The call notes of the Bicknell's and Gray-cheeked thrushes are very similar. A common call may be transcribed as a soft whee-ah or quee-a.

Foraging strategy

Forages by ground-gleaning or picking up insects or berries from the surface of the forest floor. Young are fed insects.

Diet

Eats mainly caterpillars, ants, wasps, beetles, flies; in late summer eats more fruit-blueberries, bunchberries, snowberries, red-berried alder, and wild grapes.

Behavior and displays

  • Vocal activity is high throughout June, birds can be heard singing at all times of the day and during any kind of weather.
  • The only vocal activity heard after the end of July are infrequent calls during dusk and dawn. In Vermont, singing resumes again in mid-September just before fall migration.

Courtship

  • The male pursues the female in a swift flight over his territory in the evening with his crest feathers erect and bill gaping.
  • The male performs a dance for the female, holding his body erect with head tilted upward, wings lifted above the back fluttering softly while moving back and forth on his perch with little hops.

Nesting

Nest site: Generally close to the trunk and well hidden in small- to medium-sized conifers or occasionally in a deciduous tree such as a birch.

Height: 2-12 feet (0.5-4 meters) above the ground, have been recorded as high as 25 feet (7.5 meters) in Nova Scotia.

Nest: Bulky; made mostly of twigs and moss with a little lining of dried leaves, rootlets, and other partially decomposed organic material.

Eggs: 3-4, usually 4. Bluish green, faintly spotted with brown.

Incubation period: Incubation by the female alone, 12-14 days.

Nestling period: Nestlings are altricial (born naked or with a small amount of down, eyes closed, unable to move or feed themselves). The young are fed by both parents, their feather plumes erupt from the sheaths at 6-7 days, and they leave the nest at 10-13 days.

Fledgling period: The young are dependent on their parents for food for approximately 10 days after they fledge.

Broods: One brood per season, but will lay a second clutch if nest fails early in the season.

Cowbird Parasitism: No information.

Notes

  • The Gray-cheeked Thrush and the Bicknell's Thrush were once considered a single species and were both known as the Gray-cheeked Thrush. Recent research has found that they are two distinct species because of differences in plumage, size, song, biochemistry, and range. The range of the Gray-cheeked Thrush is farther north than that of the Bicknell's Thrush.
  • Population appears to be declining in some regions, possibly due to the destruction of habitat in environmentally sensitive areas. A species of great conservation concern in the northeastern United States.
  • Recommended survey times in the northeastern United States are June 1-20 (Rimmer et al. 1996).

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