Scaup
The Greater scaup (Aythya marila) is a diving duck also known as scaup in Europe or, colloquially, "bluebill" in North America. The name of this bird may come from "scalp", a Scottish and Northern English word for a shellfish bed, or from the duck's mating call: "scaup scaup".
The adult Greater scaup has a blue bill and yellow eyes. The male has a dark head with a green sheen, a black breast, a light back, a black tail, and a white underside. The male is larger and has a more rounded head than the female. The male's belly and flanks are bright white. Its neck, breast, and tail feathers are a glossy black, while its lower flanks are vermiculated gray. The upper wing has a white stripe starting as the speculum and extending along the flight feathers to the wingtip. The legs and feet of both sexes are gray. The adult female has a brown body and head, with white wing markings similar to those of the male but slightly duller. It has a white band and brown oval-shaped patches at the base of the bill, which is a slightly duller shade of blue than the male's. Juvenile Greater scaup look similar to adult females. The male's eclipse plumage looks similar to its breeding plumage, except the pale parts of the plumage are a buffy gray.
Greater scaup breed within the Arctic Circle both in the Old World (the Palearctic) and in North America (the Nearctic). They spend the summer months in Alaska, Siberia, and the northern parts of Europe. They are also found in Asia and are present in the Aleutian Islands year-round. During summer Greater scaup inhabit wooded tundra, marshy lowland tundra, and islands in fresh water. In autumn, they migrate south for the winter. Greater scaup winter along the Pacific and Atlantic coasts of North America, the coasts of northwest Europe, the Caspian Sea, the Black Sea, the coast of Japan, the Yellow Sea, and the East China Sea. During the winter months, they are found in coastal bays, estuaries, and sometimes inland lakes, such as the lakes of Central Europe and the Great Lakes.
Greater scaup are highly social birds. They form large groups, called "rafts", that can number in the thousands. Greater scaup are active during the daylight hours. They dive to obtain food and then eat it on the surface. Due to their webbed feet and weight, Greater scaup can dive up to 6 meters (20 ft) and stay submerged for up to a minute; this allows them to reach food sources that are unobtainable to other diving ducks.
Greater scaup are omnivorous birds. They mainly eat mollusks, aquatic plants, and aquatic insects. During the summer months, they supplement their diet with small aquatic crustaceans.
Greater scaup are monogamous meaning that they form pairs. Male Greater scaup have a soft, quick whistle they use to attract the attention of females during courtship, which takes place from late winter to early spring, on the way back to their northern breeding grounds. Females have a single pitch, a raspy 'arrr-arrr-arrr-arrr-arrr' vocalization. Pairs nest in close proximity to each other in large colonies, usually near water, on an island or shoreline, or on a raft of floating vegetation. The nest consists of a shallow depression made by the female and lined with her down. After the female lays the eggs, the male abandons the female and goes with other drakes to a large, isolated lake to molt. These lakes can be close to the breeding grounds or miles away. The lakes chosen are used yearly by the same ducks. The female lays 6 to 9 olive-buff-colored eggs, which she incubates for 24-28 days. Newly hatched ducklings are covered with down and are soon able to walk, swim, and feed themselves; however, they are not able to fly until 40-45 days after hatching. The vulnerable small ducklings follow their mother, who protects them from predators. Young Greater scaup begin breeding when they are 2 years old, although they may start nesting at age one.
Although Greater scaup face numerous threats, the most significant challenge to their survival is habitat degradation caused by a mix of human development and runoff. Greater scaup, when molting and during the winter, are threatened by escalated levels of organochloride contaminants. Oil and sewage pollution also threaten these ducks. Greater scaup also often get entangled in fishing nets, thus large numbers of them drown in nets each year.
According to the IUCN Red List, the total population size of the Greater scaup is around 4,920,000-5,130,000 individuals. The breeding population in Europe consists of 134,000-178,000 pairs, which equates to 269,000-355,000 mature individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List, but its numbers today are decreasing.
