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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 male and
female adults are known as cob and pen, though these terms are
little used nowadays.
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The Northern
Hemisphere species of swan all have pure white plumage, but the
Southern Hemisphere species are all patterned with various amounts
of black. The Australian Black Swan (Cygnus atratus) is 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.
001-008.jpg
courtesy: Us Fish & Wildlife Service
009-017.jpg courtesy: National Undersea Research Program
018-019.jpg courtesy: pdphoto.org
020-021.jpg courtesy: U.S. Bureau of Land Management
022-024.jpg courtesy: USDA
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