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Swainson's thrush (''Catharus ustulatus''), also called olive-backed thrush, is a medium-sized thrush. It is a member of ''Catharus'' genus and is typical of it in terms of its subdued coloration and beautiful voice. Swainson's thrush was named after William Swainson, an English ornithologist. The breeding habitat of Swainson's thrush is coniferous woods with dense undergrowth across Canada, Alaska, and the northern United States; also, deciduous wooded areas on the Pacific coast of North America. These birds migrate to southern Mexico and as far south as Argentina. The coastal subspecies migrate down the Pacific coast of North America and winter from Mexico to Costa Rica, whereas the continental birds migrate eastwards within North America (a substantial detour) and then travel southwards via Florida to winter from Panama to Bolivia. Swainson's thrush is a very rare vagrant to western Europe. It has also occurred as a vagrant in northeast Asia.〔Brazil, Mark (2009) ''Birds of East Asia'' ISBN 978-0-7136-7040-0 page 402〕 This species may be displaced by the hermit thrush where their ranges overlap. Possibly, the latter species adapts more readily to human encroachment upon its habitat. At least in the winter quarters, Swainson's thrush tends to keep away from areas of human construction and other activity. ==Description== This species is in length. The wingspan averages at and the wing chord is . The bill measures in length and the tarsus is long. This species' body mass can range from .〔()〕〔()〕〔''Thrushes'' by Peter Clement. Princeton University Press (2001), ISBN 978-0-691-08852-5〕 This thrush has the white-dark-white underwing pattern characteristic of ''Catharus'' thrushes. Adults are brown on the upperparts. The underparts are white with brown on the flanks; the breast is lighter brown with darker spots. They have pink legs and a light brown eye ring. Birds in the east are more olive-brown on the upperparts; western birds are more reddish-brown. This bird's song is a hurried series of flute-like tones spiralling upwards. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Swainson's thrush」の詳細全文を読む スポンサード リンク
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