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The black-necked swan (''Cygnus melancoryphus'') is a swan that is the largest waterfowl native to South America. ==Description== Adults average and weigh 3.5-6.7 kg (7.7-14.8 lbs).〔del Hoyo, J. Elliott, A. and Sargatal, J.(1992) Handbook of the Birds of the World. Volume 1:Ostrich to Ducks Lynx Edicions, Barcelona〕 The wingspan ranges from .〔Ogilvie & Young, ''Wildfowl of the World''. New Holland Publishers (2004), ISBN 978-1-84330-328-2〕 The body plumage is white with a black neck and head and greyish bill. It has a red knob near the base of the bill and white stripe behind eye. The sexes are similar, with the female slightly smaller. The cygnet has a light grey plumage with black bill and feet. The black-necked swan was formerly placed in monotypic genus, ''Sthenelides''. The smallest member in its genus, it is found in freshwater marshes, lagoon and lake shores in southern South America. The black-necked swan breeds in Chilean Southern Zone, Patagonia, Tierra del Fuego and on the Falkland Islands. In the austral winter, this species migrates northwards to Paraguay and southern Brazil. The wetlands created by the Great Chilean earthquake like Carlos Anwandter Nature Sanctuary in Cruces River have become important population centers for the black-necked swan. In 2004 and 2005 thousands of black-necked swans in the Carlos Anwandter Nature Sanctuary in Chile died or migrated away following major contamination by Valdivia Pulp Mill located on the Cruces River which feeds the wetlands. By August 2005 the birds in the Sanctuary had been "wiped out"; only four birds could be observed from a population formerly estimated at 5,000 birds. Autopsies on dead swans attributed the deaths to high levels of iron and other metals polluting the water. The black-necked swan, like its nearest relatives the black and mute swan is relatively silent. Also, unlike most wildfowl, both parents regularly carry the cygnets on their backs. The female lays four to six eggs in a nest of vegetation mound. The diet consists mainly of vegetation, insects and fish spawn. Widespread and common throughout its habitat, the black-necked swan is evaluated as Least Concern on the IUCN Red List of Threatened Species.〔 It is listed on Appendix II of CITES. 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「Black-necked swan」の詳細全文を読む スポンサード リンク
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