Bewick's Swan

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Image:BewicksSwan.JPG

Common Name: Bewick’s Swan
Scientific Name: Cygnus columbianus bewickii

Size: 45-55 inches (115-140 cm); Wingspan: 62 inches (160 cm)

Habitat: Eurasia; breeding range extends across the coastal lowlands of Siberia, from the Kola Peninsula east to the Pacific. They start to arrive on the breeding grounds around mid-May, and leave for winter quarters around the end of September. The populations west of the Taimyr Peninsula migrate via the White Sea, Baltic Sea and the Elbe estuary to winter in Denmark, the Netherlands and the British Isles. They are common in winter in the wildfowl nature reserves of the Royal Society for the Protection of Birds and of the Wildfowl and Wetlands Trust. Some birds also winter elsewhere on the southern shores of the North Sea. Swans breeding in eastern Russia migrate via Mongolia and northern China to winter in the coastal regions of Korea, Japan, and southern China, south to Guangdong and occasionally as far as Taiwan. A few birds from the central Siberian range also winter in Iran at the south of the Caspian Sea; in former times these flocks also migrated to the Aral Sea before the late 20th century ecological catastrophe turned most of the habitat there into inhospitable wasteland.

Arrival in winter quarters starts about mid-October, though most spend weeks or even months at favorite resting locations and will only arrive in winter quarters by November or even as late as January. The birds leave winter quarters to breed starting in mid-February. Vagrants may occur south of the main wintering range in cold years and have been recorded from most European countries where the birds do not regularly winter, as well as Algeria, Iraq, Palestine, Libya, Nepal, NE Pakistan, and on the Marianas and Volcano Islands in the western Pacific. Vagrants on the spring migration have been sighted on Bear Island, Iceland and Svalbard, and in Alaska, Oregon and Saskatchewan in North America.

The species breeds near shallow pools, lakes and broad slow-flowing rivers with emergent littoral vegetation and pondweeds connected to coastal delta areas in open, moist, low-lying sedge-grass or moss-lichen Arctic tundra. It rarely nests in shrub tundra, and generally avoids forested areas. On migration, the species frequents shallow ponds, lowland and upland lakes, riverine marshes, shallow saline lagoons and sheltered coastal bays and estuaries. During the winter, it inhabits brackish and freshwater marshes, rivers, lakes, ponds and shallow tidal estuarine with adjacent grasslands, flooded pastures or agricultural arable fields.

Status: Least Concern. Global population: 38,000 adult individuals. The European winter population was estimated at 16,000–17,000 about 1990, with about 20,000 birds wintering in East Asia. The Iranian wintering population is small – 1,000 birds or so at most. The species population is believed to be decreasing. The species is threatened by the degradation and loss of wetland habitats due to agricultural drainage, petroleum pollution, peat-extraction, changing wetland management practices, the burning and mowing of reeds and algae population). Its Arctic breeding habitat is also threatened by oil and gas exploration. The species is threatened by mortality from oil pollution (oil spills) in molting and pre-migrational staging areas, from collisions with power lines, and from lead poisoning as a result of lead shot and fishing weight ingestion during migration and on wintering grounds. The species suffers from poaching in north-west Europe, is hunted for sport in North America and is hunted considerably for subsistence throughout its range. The species is also susceptible to avian influenza, so may be threatened by future outbreaks of the disease.

Diet: Submerged and emergent aquatic vegetation as well as grasses and grains. They often “tip up” to reach submerged aquatic vegetation and “dabble” on the water surface.

Nesting: Sexes are alike. Pens (females) are slightly smaller than cobs (males). In adult birds, the plumage is entirely white, with black feet, and a bill that is mostly black, with a thin salmon-pink streak running along the mouth line and prominent yellow in the proximal part. The iris is dark brown. Swans that frequent waters that contains large amounts of iron ions such as bog lakes, acquire a golden or rusty hue on their heads and necks.

Immatures are white mixed with some dull grey feathering, mainly on the head and upper neck, which are often entirely light grey; their first-summer plumage is quite white already, and in their second winter they molt into the adult plumage. Their bills are black with a large dirty-pink patch taking up most of the proximal half and often black nostrils, and their feet are dark grey with a pinkish hue. Downy young are silvery grey above and white below.

The Bewick’s Swans mate in the late spring, usually after they have returned to the nesting grounds; as usual for swans, they pair monogamously until one partner dies. Should one partner die long before the other, the surviving bird often will not mate again for some years, or even for its entire life.

The nesting season starts at the end of May. The pair builds the large mound-shaped nest from plant material at an elevated site near open water, and defends a large territory around it. The female lays and incubates a clutch of 3–5 eggs. The male keeps a steady lookout for potential predators. When either of them spots a threat, they give a warning sound to let their partner know that danger is approaching, Sometimes the male will use his wings to run faster and appear larger in order to scare away a predator.

The time from laying to hatching is 29–30 days. Since they nest in cold regions, Bewick’s Swan cygnets grow faster than those of swans breeding in warmer climates; the juvenile Bewick's Swan fledge 40–45 days after hatching, while those of the Whistling Swan take about 60–75 days to fledge. The fledglings stay with their parents for the first winter migration. The family is sometimes even joined by their offspring from previous breeding seasons while on the wintering grounds; Tundra Swans do not reach sexual maturity until 3 or 4 years of age.

Cool Facts: Bewick’s Swans are considered a subspecies of Tundra Swans. Bewick’s Swans are smaller than the Tundra Swan and have more black than yellow on their bills than the Whooper Swan (which resembles the Bewick’s Swan).

The bill pattern for every individual Bewick's Swan is unique, and scientists often make detailed drawings of each bill and assign names to the swans to assist with studying these birds.


Found in Songbird Remix Waterfowl Volume 3: Swans of the World

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