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The red knot (''Calidris canutus'') (just knot in Europe) is a medium-sized shorebird which breeds in tundra and the Arctic Cordillera in the far north of Canada, Europe, and Russia. It is a large member of the ''Calidris'' sandpipers, second only to the great knot.〔 Six subspecies are recognised. Their diet varies according to season; arthropods and larvae are the preferred food items at the breeding grounds, while various hard-shelled molluscs are consumed at other feeding sites at other times. North American breeders migrate to coastal areas in Europe and South America, while the Eurasian populations winter in Africa, Papua New Guinea, Australia, and New Zealand. This species forms enormous flocks when not breeding. == Taxonomy, systematics, and evolution == This Red Knot was first described by Linnaeus in the landmark 1758 tenth edition of his ''Systema Naturae'' as ''Tringa canutus''.〔 One theory is that it gets its name and species epithet from King Canute, Knot being another form of Canute; the name would refer to the knot's foraging along the tide line and the story of Canute and the tide.〔 Another etymology is that the name is onomatopoeic, based on the bird's grunting call note.〔 }} }} The diversification events may be associated with the Wisconsinan (Weichselian) glaciation 18,000 to 22,000 years ago; the opening of the ice-free corridor in North America 12,000 to 14,000 years ago; and the Holocene climatic optimum 7,000 to 9,000 years ago.〔 }} The red knot and the great knot were originally the only two species placed in the genus ''Calidris'', but many other species of sandpiper were subsequently added.〔 A 2004 study found that the genus was polyphyletic and that the closest relative of the two knot species is the surfbird (currently ''Aphriza virgata'').〔 There are six subspecies,〔 in order of size; * ''C. c. roselaari'' – (Tomkovich, 1990) – (largest) * ''C. c. rufa'' – (Wilson, 1813) * ''C. c. canutus'' – (Linnaeus, 1758) * ''C. c. islandica'' – (Linnaeus, 1767) * ''C. c. rogersi'' – (Mathews, 1913) * ''C. c. piersmai'' – (Tomkovich, 2001) – (smallest) Studies based on mitochondrial sequence divergence and models of paleoclimatic changes during the glacial cycles suggest that ''canutus'' is the most basal population, separating about 20,000 years ago (95% confidence interval: 60,000–4,000 years ago) with two distinct lineages of the American and Siberian breeders emerging about 12,000 years ago (with a 95% confidence interval: 45,000–3,500 years ago).〔〔 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「Red knot」の詳細全文を読む スポンサード リンク
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