Swans are birds of the family Anatidae within the genus Cygnus.The swans` close relatives include the 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. There are six or seven living and one extinct species of swan in the genus Cygnus; in addition, there is another species known as the coscoroba swan, although this species is no longer considered one of the true swans.
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