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Spot-billed duck
The spot-billed duck (''Anas poecilorhyncha'') sometimes referred to as the spotbill, is a dabbling duck which breeds in tropical and eastern Asia. It has three populations, treated here as subspecies, the Indian spot-billed duck (''A. poecilorhyncha poecilorhyncha''), Eastern spot-billed duck (''A. poecilorhyncha zonorhyncha''), and Burmese spot-billed duck (''A. poecilorhyncha haringtoni''). Some authors elevate the eastern population as a species, ''Anas zonorhyncha''. The name is derived from the yellow and red spot on the bill.
==Description==
This duck is around the same size as a mallard and has a scaly patterned body with a green speculum and a band of white tertials that is prominent in flight. At rest the white stripe stands out and the long neck and the bill with yellow tip and orange red spots at the base are distinctive in the nominate subspecies. It measures in length and across the wings, with a body mass of .〔''CRC Handbook of Avian Body Masses'' by John B. Dunning Jr. (Editor). CRC Press (1992), ISBN 978-0-8493-4258-5.〕〔Ogilvie & Young, ''Wildfowl of the World''. New Holland Publishers (2004), ISBN 978-1-84330-328-2〕 These are mainly grey ducks with a paler head and neck and a black bill tipped bright yellow. The wings are whitish with black flight feathers below, and from above show a white-bordered green The male has a red spot on the base of the bill, which is absent or inconspicuous in the smaller but otherwise similar female. The male does not have an eclipse plumage. Juveniles are browner and duller than adults. The legs and feet are bright orange.
The eastern spot-billed duck is darker and browner; its body plumage is more similar to the Pacific black duck. It lacks the red bill spot, and has a blue speculum.〔
Both males and females undergo a complete postnuptial moult, dropping all their wing feathers simultaneously.〔
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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