swan （天鵝) Ｄ 資料

For other uses, see Swan (disambiguation).





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Swans


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Mute Swans (Cygnus olor)

Scientific classification





Kingdom:
Animalia


Phylum:
Chordata


Class:
Aves


Order:
Anseriformes


Family:
Anatidae


Subfamily:
Anserinae


Genus:
Cygnus
Bechstein, 1803


Species


6-7 living, see text.



Synonyms


Cygnanser Kretzoi, 1957

Swans are large water birds of the family Anatidae, which also includes geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe Cygnini. Sometimes, they are considered a distinct subfamily, Cygninae.
Swans usually mate for life, though "divorce" does sometimes occur, particularly following nesting failure. The number of eggs in each clutch is between 3–8.
The word is derived from Old English swan, akin to German Schwan, in turn derived from Indo-European root *swen (to sound, to sing), whence Latin derives sonus (sound). (Webster's New World Dictionary) Young swans are known as cygnets, from the Latin word for swan, cygnus. An adult male is a cob, from Middle English cobbe (leader of a group); an adult female is a pen (origin unknown).





Contents[hide]

1 Coloration
2 Systematics and evolution
3 Role in culture
4 Photo gallery
5 References
6 External links



[edit] Coloration
The Northern Hemisphere species of swan have pure white plumage but the Southern Hemisphere species are white-and-black. The Australian Black Swan (Cygnus atratus) is completely black except for the white flight feathers on its wings, and the South American Black-necked Swan has a black neck.
The legs of swans are dark blackish grey, except for the two South American species, which have pink legs. Bill colour varies; the four subarctic species have black bills with varying amounts of yellow, and all the others are patterned red and black. The Mute Swan and Black-necked Swan have a lump at the base of the bill on the upper mandible.

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