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Evacuation
of swans.
Swans, genus Cygnus,
are 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. There are six to seven
species of swan in the genus Cygnus; in addition there
is another species known as a swan, the Coscoroba Swan,
although this species is no longer considered related
to the true swans. Swans usually mate for life, though
'divorce' does sometimes occur, particularly following
nesting failure. The number of eggs in each clutch ranges
from three to eight...
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