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White-winged duck
The white-winged duck or white-winged wood duck (''Asarcornis scutulata'') is a large species of duck, formerly placed in the genus ''Cairina'' and allied with the dabbling ducks. However, mtDNA cytochrome ''b'' and NADH dehydrogenase subunit 2 sequence analysis and the biogeographical pattern of distribution indicate that the anatomical similarity to the Muscovy duck is deceiving. Thus, this species might more appropriately be placed in a monotypic genus, as ''Asarcornis scutulata'', which appears to be unrelated to the Muscovy duck but closer to the diving ducks.
==Description==
This is one of the largest species of duck. In fact, among all wild species called duck, only the steamer ducks are larger and heavier on average. The muscovy duck also attains sizes that nearly rival the white-winged duck but may average a bit smaller in a wild state. Length is and wingspan is .〔Ogilvie & Young, ''Wildfowl of the World''. New Holland Publishers (2004), ISBN 978-1-84330-328-2〕 Males weigh , while females weigh .〔(''Cairina scutulata'' – White-winged duck ). wildpro.twycrosszoo.org〕〔''CRC Handbook of Avian Body Masses, 2nd Edition'' by John B. Dunning Jr. (Editor). CRC Press (2008), ISBN 978-1-4200-6444-5.〕 The most noticeable feature on adult birds, is the dark body contrasting with a whitish head and neck. Males have mostly dull yellowish bill, blackish mottling on the head and upper neck, white lesser median coverts and inner edges of tertials and bluish-grey secondaries. In flight, white wing-coverts contrast with the rest of the wings. Females are smaller and usually have more densely mottled head and upper neck. The juvenile is duller and browner.〔(White-winged Duck ''Cairina scutulata'' ). Birdlife International. birdlife.org〕
This secretive species is only known to feed at night. Its diet consists of seeds, aquatic plants, grain, rice, snails, small fish and insects.〔 It inhabits stagnant or slow-flowing natural and artificial wetlands, within or adjacent to evergreen, deciduous or swamp forests, on which it depends for roosting and nesting, usually in tree-holes. Although lowlands (below c.200 m) provide optimum habitat, it occurs up to 1,400 m of altitude, especially on plateaus supporting sluggish perennial rivers and pools.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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