Cygnus columbianus bewickii
(a subspecies of Tundra Swan)
These are the smallest of the northern swans, weighing around 6.4kg (male) 5.8kg (female). They nest in the Arctic tundra and migrate some 4000km from the breeding grounds to their wintering sites in Europe (mainly Denmark, Germany, Holland and the UK). As they have uniquely variable bill patterns, individuals can be identified by trained observers. There are records of a Jankowski Swan, sometimes referred to as the Eastern Bewick's Swan, which breeds from the Lena Delta to the Anadyr River on the Bering Sea.
This swan does have a higher, straighter bill which is more angular near the base and has a longer yellow patch. It is not recognised as a distinct species.