The White-winged Scoter (Melanitta deglandi) is a large sea duck.

Description

It is characterised by its bulky shape and large bill. This is the largest species of scoter. Females range from 950-1950 grams (2.1-4.2 lb) and 48-56 cm (19-22 inches), averaging 1180 grams (2.6 lb) and 52.3 cm (21 inches). She is brown with pale head patches. The male ranges from 1360-2128 grams (3-4.7 lb) and from 53-60 cm (21-24 inches), averaging 1380 grams (3.6 lb) and 55 cm (22 inches). He is all black, except for white around the eye and a white speculum. This scoter's bill has a black base and a large knob.

There are a number of differing characteristic of the Eastern Siberian race and the American race from Alaska and Canada to west of the Hudson Bay. Males of the American subspecies have browner flanks, dark yellow coloration of most of the bill and a less tall bill knob, approaching the Velvet Scoter. The Asian form has a very tall knob at the base of its mostly orange-yellow bill. Females are identical in the field.

Taxonomy

It is sometimes considered to be conspecific with the Velvet Scoter. These two species, and the Surf Scoter, are placed in the subgenus Melanitta, distinct from the subgenus Oidemia, Black and Common Scoters. Many authorities regard the Asian race (M. d. stejnegeri) and the American race (M. d. deglandi) as separate species now.

Distribution

The White-winged Scoter breeds over the far north of Asia east of the Yenisey Basin, and North America. It winters further south in temperate zones, on the Great Lakes, the coasts of the northern USA and the southern coasts of Canada, and Asia as far south as China. It forms large flocks on suitable coastal waters. These are tightly packed, and the birds tend to take off together.

Behaviour

Breeding

The lined nest is built on the ground close to the sea, lakes or rivers, in woodland or tundra. 5-11 eggs are laid. The pinkish eggs average 46.9 mm (1.8 inches) in breadth, 68.2 mm (2.7 inches) in length and 82.4 grams (2.9 oz) in weight. The incubation period can range from 25 to 30 days. After about 21 days, neighboring females may start to behave aggressively towards other nesting females, resulting in confusion and mixing of broods. By the time she is done brooding, a female may be tending to as much as 40 offspring due to the mixing from these conflicts. The female will tend to her brood for up to 3 weeks and then abandon them, but the young will usually stay together from another 3 weeks. Flight capacity is thought to be gained at 63 to 77 days of age.

Food

In freshwater, this species primarily feeds on crustaceans and insects; while in saltwater areas, it feeds on molluscs and crustaceans. The favorite foods of the American (sub)species are an amphipod (Hyalella azteca) in freshwater, and rock clams (Protothaca staminea), Atlantic razors (Siliqua spp.) and Arctic wedge clams (Mesodesma arctatus).

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