Bewick’s swan (Cygnus columbianus bewickii) takes its name from the bird illustrator Thomas Bewick (1753-1828). It was only recognized as a separate wild swan species in 1830, this being done by the amateur ornithologist William Yarrell (1784-1856) who named it in honour of Thomas Bewick.
Bewick’s swan is a winter migrant to the British Isles, from October to April, as it breeds in the tundra regions of Siberia. Another wintering ground, for birds in eastern Siberia, is coastal China and Japan.
Bewick’s swan is the smallest of the northern swans, measuring up to 48 inches (120 cms) in length. The plumage is pure white, apart from a rusty coloured stain that is sometimes present on the head and neck. The sexes are similar in appearance.
The black bill has a yellow area at its base – this is similar to what is seen on whooper swans, but smaller. It was noted by the naturalist Sir Peter Scott that the yellow patches on the faces of Bewick’s swans were infinitely variable and could be used to distinguish one individual from another.
Bewick’s swans have several features in common with geese. These include its short neck and rounded head and its habit of flying in groups in V-shaped formation while honking softly. These groups can be hundreds strong.
The main food of Bewick’s swans is leaves, roots and the stems of aquatic plants, which they take by up-ending in shallow water. In winter they add seeds and grasses to their diet, as well as scraps gleaned from farmed fields.
The breeding season is from early May, in the south of their nesting range, and from late May or early June further north.
Nests are built on small islands in lakes and river estuaries. A conical mound is constructed from mosses, sedges and lichens, lined with feathers and down. A pair will return to same nest in succeeding years, adding fresh material. A nest can therefore grow in size to as much as 30 inches (75cms) in height.
Up to five eggs are laid, which take up to 30 days to hatch. Incubation is only done by the female. Both adults tend the chicks, which are ready to fledge in around 40 to 45 days.
Bewick’s swans are not as plentiful as they once were, despite being protected over most of their range. Threats include habitat loss, lead poisoning and illegal hunting.