Tundra Swan
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The Tundra Swan (Cygnus columbianus) is a small Holarctic swan. The two taxa within it are conventionally [2] regarded as conspecific, but are also sometimes[3] 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.
Description[4]Bewick's is the smallest of the Holarctic swans, at 115-146 cm (45-58 in) in length, a 170-195 cm (67-77 in) wingspan and a weight range of 4-9.5 kg (8.8-21 lbs). 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.
DistributionThe Tundra Swan breeds in the Arctic, C. c. bewickii right across northern Russia from the Kola Peninsula east to the Pacific, C. c. columbianus in Alaska and Canada. C. c. bewickii migrates via the White Sea, Estonia and the Elbe estuary, to winter in the Netherlands and the British Isles, notably in the wildfowl nature reserves of the Royal Society for the Protection of Birds and of the Wildfowl and Wetlands Trust; populations breeding in eastern Russia winter in Japan and China. C. c. columbianus winters in the southwestern USA.[4] Ecology and behaviourIn summer, their diet consists mainly of aquatic vegetation, eaten while swimming. At other times of year, they also eat cultivated grains in open fields. According to National Geographic[citation needed], when migrating these birds can fly at altitudes of nearly 27,000 ft. 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.[5] The Bewick's Swan is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies. Footnotes
References
External links Wikimedia Commons has media related to:
cs:Labuť malá de:Zwergschwan es:Cygnus columbianus eo:Malgranda cigno fr:Cygne siffleur fy:Lytse Swan is:Dvergsvanur lt:Mažoji gulbė nl:Kleine zwaan ja:コハクチョウ no:Dvergsvane pl:Łabędź czarnodzioby ru:Американский лебедь sk:Labuť tundrová fi:Pikkujoutsen sv:Mindre sångsvan tr:Küçük kuğu |
