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The least tern (''Sternula antillarum'', formerly ''Sterna antillarum'') is a species of tern that breeds in North America and locally in northern South America. It is closely related to, and was formerly often considered conspecific with, the little tern of the Old World. Other close relatives include the yellow-billed tern and Peruvian tern, both from South America. It is a small tern, long, with a wingspan of , and weighing . The upper parts are a fairly uniform pale gray, and the underparts white. The head is white, with a black cap and line through the eye to the base of the bill, and a small white forehead patch above the bill; in winter, the white forehead is more extensive, with a smaller and less sharply defined black cap. The bill is yellow with a small black tip in summer, all blackish in winter. The legs are yellowish. The wings are mostly pale gray, but with conspicuous black markings on their outermost primaries. It flies over water with fast, jerky wingbeats and a distinctive hunchback appearance, with the bill pointing slightly downward. It is migratory, wintering in Central America, the Caribbean and northern South America. Many spend their whole first year in their wintering area.〔 It has occurred as a vagrant to Europe, with one record in Great Britain. It differs from the little tern mainly in that its rump and tail are gray, not white, and it has a different, more squeaking call; from the yellow-billed tern in being paler gray above and having a black tip to the bill; and from the Peruvian tern in being paler gray above and white (not pale gray) below and having a shorter black tip to the bill. ==Subspecies== The differences among the three subspecies may not be as much as had been thought.〔〔 * ''S. a. athalassos'' – (Burleigh & Lowery, 1942): Breeds on the rivers of the Arkansas River, Mississippi River, Brazos River, Trinity River, and Rio Grande basins;〔 winters south to northern Brazil. * ''S. a. antillarum'' – (Lesson, 1847): nominate, Breeds on the Atlantic coast of North America, from Maine south along the east and south coasts of the United States, Bermuda, the Caribbean, and Venezuela; winters south to northern Brazil. * ''S. a. browni'' – (Mearns, 1916): California least tern. Breeds on the Pacific coast of North America, from central California south to western Mexico; winters mainly in Central America. 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「Least tern」の詳細全文を読む スポンサード リンク
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