The Tundra Swan (Cygnus columbianus) is a small Holarctic swan. Tundra Swans are sometimes separated in the genus Olor together with the other Arctic swan species.
The Tundra Swans mate in the late spring, usually after they have returned to the nesting grounds; as usual for swans, they pair monogamously until one partner dies. Should one partner die long before the other, the surviving bird often will not mate again for some years, or even for its entire life. The nesting season starts at the end of May.
The time from laying to hatching is 29–30 days for Bewick's Swan and 30–32 days for the Whistling Swan. Since they nest in cold regions, Tundra Swan cygnets grow faster than those of swans breeding in warmer climates; those of the Whistling Swan take about 60–75 days to fledge – twice as fast as those of the Mute Swan for example – while those of Bewick's Swan, about which little breeding data is known, may fledge a record 40–45 days after hatching already. The fledglings stay with their parents for the first winter migration. The family is sometimes even joined by their offspring from previous breeding seasons while on the wintering grounds; Tundra Swans do not reach sexual maturity until 3 or 4 years of age.
Source: en.wikipedia.org/wiki/Tundra_Swan - 18.09.2011