Cygnus (swan)

Swans
Mute Swan with cygnets Larger version
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Aves Order: Anseriformes Family: Anatidae Subfamily†: Anserinae
Genera
Cygnus Coscoroba
† see also: Goose Anatidae

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.

Swans usually mate for life, though "divorce" does sometimes occur, particularly following nesting failure. The number of eggs in each clutch varies both within and among swan species, typically between 3-8 eggs.

Young swans are known as cygnets, from the Latin word for swan, cygnus.

The Northern Hemisphere species of swan are all pure white in plumage, but the Southern Hemisphere species are all patterned with various amounts of black. The Australian Black Swan (Cygnus atratus) is blackest, black all over except for the white flight feathers on its wings, and the South American Black-necked Swan has, as its name suggests, a black neck; finally, the Coscoroba Swan, also from southern South America, has black tips to the primary feathers. The legs of all swans are dark blackish grey, except for the two South American species, which have pink legs. Bill colour varies rather more; the three far northern species have black bills with varying amounts of yellow, and all the others varyingly patterned red and black. The Mute Swan and Black-necked Swan have a curious lump at the base of the bill on the upper mandible.

Species of swan:

• Genus Cygnus
  • Whooper Swan, Cygnus cygnus breeds in Iceland and subarctic Europe and Asia, migrating to temperate Europe and Asia in winter.

Trumpeter Swan
Larger version

• Trumpeter Swan, Cygnus buccinator is a North American species very similar to the Whooper Swan (and sometimes treated as a race of it), which was hunted almost to extinction but has since recovered: it is one of the heaviest flying animals, at up to 17 kilograms (38 pounds).

• Tundra Swan, Cygnus columbianus is a relatively small swan which has two major subspecies (sometimes treated as a distinct species); as the name suggests, it breeds on the Arctic tundra, further north than other swans.
  • Bewick's Swan, Cygnus columbianus bewickii is the Eurasian form which migrates from Arctic Russia to western Europe and eastern Asia (China, Japan) in winter. The reserves of the Royal Society for the Protection of Birds and of the Wildfowl and Wetlands Trust in Britain are important for Bewick's and Whooper Swans.
  • Whistling Swan, Cygnus columbianus columbianus is the North American race, which is sometimes considered a separate species from Bewick's swan.

• Mute Swan, Cygnus olor, is a common temperate Eurasian species, often semi-domesticated; descendants of domestic flocks are naturalized in the United States and elsewhere.

Mute Swans

• Black Swan, Cygnus atratus of Australia, and introduced in New Zealand. The Black Swan is the official state emblem of Western Australia.
• Black-necked Swan, Cygnus melanocoryphus of South America, formerly Sthenelides melanocorypha.