[order] Anseriformes | [family] Anatidae | [latin] Cygnus columbianus | [UK] Tundra Swan | [FR] Cygne de Bewick | [DE] Zwergschwan | [ES] Cisne Chico | [IT] Cigno minore | [NL] Kleine Zwaan

Kleine Zwaan determination

copyright: J. del Hoyo

In direct comparison appreciably the Bewick's Swan Cygnus columbianus is smaller (L 120 cm) than Mute Swan (Cygnus olor), with shorter neck, less elongated head shape and less yellow on bill. This species, formerly known as the Whistling Swan, is a large bird with white plumage and black legs, feet, and beak. However, when it is feeding in iron-rich areas, the feathers on its head and neck may take on a reddish tinge.
The male weighs on average 7.5 kg and can measure 1.3 m from bill to tail. The adult female is about the same size as the male but weighs slightly less, about 6.3 kg. The young of the year are smaller than the adults and have grey plumage, pinkish beaks with black tips, and pink legs and feet. It takes at least two years for adult plumage to grow in.

Bewick's Swans spend the summer on the tundra of the Canadian Arctic and Alaska. Each pair of Bewick's Swans defends a large territory that may be more than 2 km2.

This swan is breeding in the Eurasian tundra, from the Finno-Russian border to Central Siberia. The birds breeding West of the Taymyr Peninsula are wintering mainly in Denmark, the Netherlands, England and Ireland. A few birds also reach the Rhone Delta in southern France. Elsewhere the species is of only very occasional occurrence during strong winters. The total population visiting Western Europe is estimated at 17000 individuals, and seems to be stable

Bewick's Swans feed mainly on the tubers and roots of aquatic plants that grow at shallow depths in fresh, brackish, or salt water. They reach this food by extending the head and neck downward, frequently tipping the body but seldom completely submerging. On the Atlantic coast the swans vary their diet with molluscs, or hard-shelled water animals, such as mussels and clams. In recent years, they have begun to feed extensively on grains, such as corn and wheat that are left on the ground after the harvest.

This species has a large range, with an estimated global Extent of Occurrence of 100,000-1,000,000 kmē. It has a large global population estimated to be 300,000 individuals (Wetlands International 2002). Global population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern. [conservation status from birdlife.org]

The courtship and pairing of young adult birds is in full swing in late winter and continues through the spring migration. Adults already paired reinforce their bond by vocal and visual displays. The most spectacular of these is the so-called victory display in which male and female face each other, extend and wave the wings slowly, bow the head and neck forward and backward, and, in duet, produce a formalized sequence of loud, melodious sounds. The pair-bond is strong and probably lasts for life.
They are solitary nesters with each pair defending a large territory that may be more than 2 km2. The nest is a large conical affair of sticks, often placed on a hummock and lined with moss, sedges, and grasses. It is usually quite close to a tundra pond or lake that is large enough to provide a good feeding and loafing area for the young but not too large to defend against other breeding pairs. Nests in favourable locations tend to be re-used each year.
Bewick's Swans usually do not breed until their fourth or fifth year. A year before breeding, pairs normally "go steady" and select and defend a territory without actually nesting. When they reach breeding age, they begin to nest in late May or early June before the snow is off the tundra, while many of the lakes are still frozen. The cream-coloured, elliptical-ovate eggs average 107 mm in length. A clutch of four eggs is normal; in exceptionally warm, favourable springs the female often lays five or six eggs. An unusually cold and snowbound spring, on the other hand, may inhibit nesting for that year. Not all adult pairs nest every year.
Incubation, or warming of the eggs until they hatch, begins when the final egg is laid and lasts about 32 days. Only the female incubates the eggs, but the male remains close by, guarding the nest site and defending the territory. If the eggs are destroyed, renesting will not take place.
The downy ash-grey cygnets emerge in early July and weigh about 180 g. They are soon able to hunt for their own food; both parents help them find suitable plant food around the margins of the pond. They need to be brooded, or kept warm by a parent sitting on them, frequently, to protect them from the cold and the onslaughts of numerous mosquitos. The early casualty rate among cygnets is quite high, chiefly due to cold or starvation.
The family remains on the territory during August, when the adults undergo a moult period, or shed feathers. They are flightless for several weeks, until new primary wing feathers replace those that have been shed. If all goes well, the cygnets' growth rate is very rapid and in September, after about 70 days, their weight may be 28 times the hatching weight. This growth rate is necessary, because by early September the cygnets must be fully feathered and able to fly well enough to travel to larger lakes that will freeze over more slowly.
At these lakes they encounter young, non-breeding birds of the previous year and unsuccessful nesters or unpaired adults that have spent the summer in small groups in favourable feeding locations. From these points, the flocks begin the early stages of migration as freeze-up approaches. An early winter will doom cygnets not yet ready to fly out of the north.

Migratory; winters in temperate areas; sporadically in more southern latitudes during cold winters. Rare vagrant to Pakistan.