There are three species of swans in North America.
The Trumpeter Swan (Cygnus buccinator) and
Tundra Swan (C. columbianus) are indigenous,
while the Mute Swan (Cygnus olor) is a Eurasian species
that has been introduced and now breeds in the wild in some areas.

All three are very large all-white birds.
The male swan is called the Cob.
He typically weighs more and looks larger than the female (the Pen).
Young-of- the-year swans are called Cygnets.


http://www.trumpeterswansociety.org/swan-identification.html