White-winged Scoter (Melanitta deglandi)

[order] ANSERIFORMES | [family] Anatidae | [latin] Melanitta deglandi | [authority] Linnaeus, 1758 | [UK] White-winged Scoter | [FR] Macreuse a ailes blanches | [DE] Amerikanische Samtente | [ES] Negron Especulado | [NL] Witvleugel Zee-eend | [copyright picture] Gary Kramer

Subspecies

Genus

Physical charateristics

The white-winged scoter is the largest of the three scoters. Adult males are 53?58 cm (21? 23 in.) long and weigh 1,360?1,780 grams (3?4 lbs); adult females are slightly smaller. They are distinguished from other scoters by the all-white patch (speculum) on the secondary feathers of their wings, which is obvious in flight and sometimes visible at rest. Adult males are entirely blackish with a small white, teardrop-shaped patch around its eye. Its orange bill has a black hump at the base and is somewhat wedge-shaped. Females and juveniles of both sexes are dark brownish with paler bellies; females and juveniles have a dark bill and variable amounts of white on their head that can appear as spots.

Range

North America : North. The winter range of white-winged scoters includes the Pacific and Atlantic coasts, where they prefer coastal environments, especially bays and inlets. They migrate to the Atlantic and Pacific coasts from breeding areas in northwestern Canada and Alaska.

Habitat

Prefers coastal salt and brackish waters, less commonly on inland fresh waters. Nests on islands or shores inland ponds, lakes or slow-moving streams in wooded, bushy, or overgrown sites, or, less commonly, in concealed or bare sites in open tundra or prairie. Strongly philopatric to nesting areas

Reproduction

Females return each year to nest near the area where they were hatched, occasionally using the nests of other birds. Nest predators seem to play an important role in influencing nest site selection because the females consistently choose nest sites that are long distances from water (usually 25?100 m; 80?325 ft) and are often concealed under dense or thorny vegetation, In some areas, they nest predominantly on islands, although gulls, ravens, and crows often destroy 10-30% of nests there. Nests are shallow depressions. The female adds down to the nest when the clutch is complete, and incubates 5?12 eggs for 26?29 days. Young from several broods may join to form large aggregations called creches, which are attended by one to three females. Only a few young scoters survive to adulthood – most deaths occur in the first few weeks of life. The chief predators are large gulls. Precocial young are tended by female, young are able to fly at 63?77 days.

Feeding habits

The diet changes dramatically when it moves from saltwater wintering areas to freshwater breeding sites. Coastally, it typically feeds only during daytime in depths <5 m, but up to 20 m (60 ft), mostly on bottom-dwelling animals such as mollusks (clams, mussels, snails and periwinkles) and crustaceans (crabs, shrimp). Small items are swallowed under water, but large foods are brought to the surface and swallowed whole. On freshwater breeding sites, the bird feeds primarily on insect larvae and amphipods.

Video White-winged Scoter

httpv://www.youtube.com/watch?v=n2YhbeTjKcc

copyright: Helmut Schenkel Brunner

Conservation

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Because of this species’ low rate of recruitment and strong philopatry (tendency to return to the same nesting area), disturbance during the nesting season and hunting on breeding areas have the potential to severely impact local populations. During 1955-’73, estimates of the white-winged scoter population ranged from 555,000 to 675,000 birds. Currently, accurate population information is not available for white-winged scoters. However, midwinter inventories indicate a declining trend from 1954 to 1994.

Migration

White-winged scoters nest on freshwater and brackish lakes in the boreal forests of northwestern Canada and Alaska with scattered populations on the prairies and parklands in Manitoba, Saskatchewan, and Alberta. They winter in large bays and estuaries along the Pacific and Atlantic coasts from the Aleutian Islands of Alaska to southern and Baja California and from Newfoundland to Texas. About 70 percent of the Atlantic white-winged scoter population appears to winter between Long Island Sound and Virginia, with greatest numbers in Chesapeake Bay. A few winter on the eastern Great Lakes as well.

Distribution map