The Tundra Swan (Cygnus columbianus) is a small Holarctic swan. The two taxa within it are conventionally regarded as conspecific, but are also sometimes split into two species, Cygnus bewickii (Bewick's Swan) of the Palaearctic and the Whistling Swan C. columbianus of the Nearctic. Bewick's Swan is named after the engraver Thomas Bewick, who specialised in illustrations of birds and animals.
Birds from eastern Russia (roughly east of the Taimyr Peninsula) are sometimes separated as the subspecies C. c. jankowskii, but this is not widely accepted as distinct, most authors including them in C. c. bewickii.
C. c. bewickii is similar in appearance to the Whooper Swan, but is smaller, shorter-necked and has a more rounded head shape, with variable bill pattern, but always showing more black than yellow (the other way around as with Whooper Swans) and tending towards a blunt forward edge of the yellow (Whooper tends towards a more pointed edge). The bill pattern for every bird is unique, and scientists can make detailed drawings of each and give them names to assist with studying this species.
The Whistling Swan is distinguished from C. c. bewickii by its largely black bill with a small yellow spot of variable size at the base. C. c. columbianus also averages one-third bigger than C. c. bewickii. It is distinguished from the Trumpeter Swan of North America by that species' larger size and large bill, which is lined with salmon-pink along the mouthline instead of the yellow dot on the lores.
Females are slightly smaller than males. The immature birds have some dull grey feathering, mainly on the head, and bills with a large dirty pink patch. Their feet are also lighter. In birds living in water that contains large amounts of iron ions like bog lakes, the head and neck plumage acquires a golden hue. They have a high-pitched honking call similar to a Canada Goose. Contrary to its common name, the ground calls of the Whistling swan are not a whistle and neither notably different from that of Bewick's Swan. The flight call of the latter is a soft ringing bark like bow-wow..., the Whistling Swan gives a markedly high-pitched trisyllabic bark like wow-wow-wow in flight.
Note that color variations with more or less yellow or pink instead of yellow or black are not exceptional, especially in the Palearctic birds.
The Tundra Swans mate in the late spring and are usually up north nesting. Since it gets colder up north, the cygnets grow much faster than the usual swans that are raised in the moderate climate lands. They tend to be territorial to many animals who pass by. The Pen is always watching when she is incubating her eggs on the nest. The Cob is always on the look out for animals heading nearby to the female swan. Then when either of them spot danger they make a sound of warning to let them both know that danger is approaching. Sometimes the male will run using its wings to make him faster when running to scare away the predator. Arctic Foxes are much more harder to scare away as they are just like Raccoons who are very hard in the countries of Canada, Eastern Asia and Europe. These birds are unlike Mute Swans. The Tundra Swans are migratory birds like the Trumpeter Swans and other swans. Mute Swans are non- migratory birds so they are separated from these migratory birds.
Their breeding habitat is tundra. The female bird lays 4 to 7 eggs in a mound of plant material on a site near open water. The pair build the nest and defend a large territory around it. They pair for life, and their cygnets stay with them all winter; they are sometimes joined by offspring from previous years.
Healthy adult birds have few natural predators. Although numbers are stable over most of its range, they are increasingly dependent on agricultural crops to supplement their winter diet due to loss of aquatic vegetation in their winter habitat as a result of habitat destruction and water pollution. The Whistling Swan's numbers seem to be slowly declining in the West since the late 19th century, coincident with the expansion of human settlement and habitat conversion in the birds' wintering areas.
The Bewick's Swan is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.