Greater scaup

Greater Scaup Temporal range:
Adult male in California
Adult female in California
Conservation status
Least Concern  (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Anseriformes
Family:	Anatidae
Subfamily:	Aythyinae
Genus:	Aythya
Species:	A. marila
Binomial name
Aythya marila (Linnaeus, 1761)
Subspecies
A. m. marila (Linnaeus, 1761) (Eurasian Greater Scaup) A. m. nearctica (Stejneger, 1885) (Nearctic Greater Scaup)
Greater Scaup range map

The Greater Scaup (Aythya marila), just Scaup in Europe, or colloquially "Bluebill" in North America for its bright blue bill, is small compared to other diving ducks; however, it is larger than the closely related Lesser Scaup. The scientific name Aythya marila comes from the Ancient Greek word for an unidentified seabird. It is a circumpolar duck, which means that its range circles one of Earth's poles. It spends the summer months breeding in Alaska, northern Canada, Siberia, and the northernmost reaches of Europe. During the winter, it migrates south down the coasts of North America, Europe, and Japan.

Drake Greater Scaup are larger and have more rounded heads than females; they have a bright blue bill and yellow eyes. They have dark heads with a glossy green tint, white undersides and wings with white on the tips. The females are mostly brown, with white bands located on their wingtips. They have a blue bill that is slightly duller then the drake's.

Greater Scaup nest near water, typically on islands in northern lakes or on floating mats of vegetation. They begin breeding at age two, but start building nests in the first year. The drakes have a complex courtship procedure, which takes place on the return migration to the summer breeding grounds and concludes with the formation of monogamous pairs. Females lay a clutch of six to nine olive-buff colored eggs. The eggs hatch in 24 to 28 days. The down-covered ducklings are able to follow their mother in her search for food immediately after hatching.

Greater Scaup eat aquatic mollusks, plants, and insects, which they obtain by diving underwater. They form large groups, called "rafts", that can number in the thousands. Their main threat is human development, although they are preyed upon by owls, skunks, raccoons, foxes, coyotes, and humans. Greater Scaup populations have been declining since the 1980s; however, they are still listed as a species of least concern by the IUCN Red List.

Taxonomy

The scientific name for Greater Scaup, Aythya marila, comes from the Ancient Greek word for an unidentified seabird. The Greater Scaup was first studied by Linnaeus in 1761. The Greater Scaup in America are distinguishable from the same species in Europe and Asia by stronger vermiculation, worm-like carvings or marks on the mantle and scapulars, and are considered a separate subspecies, A. m. nearctica. Based on size differences, a Pleistocene paleosubspecies, Aythya marila asphaltica, has also been described from fossils recovered at Binagady, Azerbaijan. The Greater Scaup's name may come from "scalp", a Scottish and Northern English word for a shellfish bed,or from the duck's mating call: "scaup scaup".

A phylogenetic analysis of the diving ducks, examining the skeletal anatomy and skin, found that the Greater and Lesser Scaups are each others' closest relatives, with the Tufted Duck as the next closest relative of the pair.

Description

The adult Greater Scaup is 39–56 cm (15–22 in) long with a 71–84 cm (28–33 in) wingspan and a body mass of 726–1,360 g (1.601–2.998 lb). It has a blue bill and yellow eyes and is 20% heavier and 10% longer than the closely related Lesser Scaup. The male has a dark head with a green sheen, a black breast, a light back, a black tail, and a white underside. The drake or male Greater Scaup is larger and has a more rounded head than the female. The drake's belly and flanks are a bright white. Its neck, upper chest, and tail feathers are a glossy black, while its lower flanks are gray. The drake also has a white speculum on its wings. The adult female 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 drake's bill. Females have grey on both their legs and feet. They have a brown body and head, with white bands on their wingtips. Juvenile Greater Scaup look similar to to adult females. The Greater Scaup drake's eclipse plumage looks similar to its breeding plumage, except the pale parts of the plumage are a buffy gray.

Distribution and habitat

The Greater Scaup is a circumpolar duck, which means that its range circles one of Earth's poles. It spends the summer months in Alaska, Siberia. and the northern parts of Europe. It is also found in Asia, and is present in the Aleutian Islands year round. The summer habitat is marshy lowland tundra and islands in fresh water lakes. In the fall, the Greater Scaup populations start their migration south for the winter. They 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, Yellow Sea and 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.

In Europe, the Greater Scaup breeds in Iceland, the northern coasts of the Scandinavian peninsula, including much of the northern parts of the Baltic Sea, the higher mountains of Scandinavia and the areas close to the Arctic Sea in Russia. These birds spend the winters in the British Isles, western Norway, the southern tip of Sweden, the coast from Brittany to Poland, including all of Denmark, the Alps, the eastern Adriatic Sea, the northern and western Black sea and the southwestern Caspian Sea.

In North America, the Greater Scaup summers in Newfoundland and Labrador, along with Ungava Bay, the Hudson Bay, Lake Winnipeg, Northern Yukon, Northern Manitoba, and Northern Saskatchewan. It winters in Nova Scotia New Brunswick, and the entire west coast of British Columbia. It will also winter along the entire west coast of North America, including the Baja Peninsula. The Greater Scaup also winters along the shores of the Great Lakes, the Gulf of Mexico and the entire east coast from Maine to Florida.

Behaviour

Breeding

Greater Scaup breed all the way from Iceland to northern Scandinavia, northern Russia, northern Siberia and the western North American Arctic. They breed in the tundra and the boreal forest; it is estimated that 75% of the North American population breed in Alaska. Greater Scaup typically nest on islands in large northern lakes. Greater Scaup begin breeding when they are two years old, although they may start nesting at age one. Drake Greater Scaup have a soft quick whistle to get the attention of hens during their courtship which takes place from late winter to early spring, on the way back to their northern breeding grounds. Female Greater Scaup have a single pitch, a raspy “arrr-arrr-arrr-arrr-arrr” sounding vocalization. The courtship procedure is complex and results in the formation of monogamous pairs. 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 drake abandons the female. The female lays six to nine olive-buff colored eggs, which she incubates for 24–28 days. Newly hatched chicks 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 chicks follow their mother, who protects them from predators.

Feeding

Several Greater Scaup feeding in Tokyo bay, Japan

The Greater Scaup mainly eats mollusks, aquatic plants, and aquatic insects, which it obtains by diving underwater. During the summer months, the Greater Scaup will eat small aquatic crustaceans. There is a report of four Greater Scaups swallowing leopard frogs (with body length about 5 cm (2 inches)), which they dredged out of a roadside freshwater pond. In freshwater ecosystems, the Greater Scaup will eat seeds, leaves, stems and roots, along with sedges, pondweeds, muskgrass, and wild celery. Owing to the Greater Scaup's webbed feet and weight, it can dive up to 6 metres (20 ft) and stay submerged for up to a minute, allowing it to reach food sources that other diving ducks are unable to take advantage of. The Greater Scaup forms large flocks, some of which can contain thousands of birds. When flocks are in water that has a current they will face it, and as the ducks float backwards, some fly to the front of the flock to keep them in the same position. The ducks in the flock dive to obtain food, which they eat on the surface.

Threats

Common predators of the Greater Scaup consist of owls, skunks, raccoons, foxes, coyotes, and humans. Although the Greater Scaup has several predators, the most significant threat to its survival is habitat degradation caused by a mix of human development and runoff. Greater Scaup, when moulting and during the winter, are threatened by escalated levels of organochloride contaminants. Oil and sewage pollution also threaten the Greater Scaup. Greater Scaup often find themselves entangled in fishing nets, thus large numbers of them drown in nets each year. Greater Scaup can catch avian influenza, so future outbreaks have the potential to threaten Greater Scaup populations.

A joint group of American and Canadian scientists researching Scaup migration across the Great Lakes found that 100% of female Greater Scaup, and 77% of female Lesser Scaup, had escalated levels of selenium in their bodies. Selenium is a occurring semimetallic trace element that occurs naturally in some soils and is necessary for Greater Scaup at low levels. However excessive selenium can cause reproductive harm and is highly toxic. On their migration across the Great Lakes, Greater Scaups are at risk of ingesting selenium by eating the invasive zebra mussels, which can render a hen infertile. This sterilization of hens is causing the population to decrease.

Conservation

Drake with a leg band in North Carolina

Greater Scaup are rated as a species of least concern by the IUCN Redlist. During aerial population surveys Greater and Lesser Scaup are counted together, because they look almost identical from the air. It was estimated that the Greater Scaup made up about 11% of the continental Scaup population. Since the 1980s, Scaup populations have been steadily decreasing. Some of the primary factors contributing to this decline are habitat loss, contaminants, changes in breeding habitat, and a lower female survival rate. The 2010 American Scaup population survey was 4.2 million Scaup, however, the worldwide Greater Scaup population survey estimated 1,200,000 to 1,400,000 mature Greater Scaup. Along with the aerial population surveys, there is a banding program for the Greater Scaup. Metal leg bands are placed on them, so that if the Scaup is killed by a hunter or if it is captured by another banding group, the number on the band can be reported to biologists and wildlife organizations. These banding programs yield valuable data about migration patterns, harvest rates, and survival rates.

A major threat to the Greater Scaup is habitat degradation in the Atlantic Flyway. Since 80% of the Greater Scaup population winters in the urbanized part of the Atlantic Flyway, these ducks are subject to higher levels of organic contaminates, along with increased levels of heavy metals in foods and habitat, and in some cases, the Greater Scaup themselves.

Human interactions

File:Greater scaup.jpg

A typical drake decoy

Greater Scaup are a popular game bird in North America and Europe. They are hunted in Denmark, Germany, Greece, France the United Kingdom, and Ireland, and in Iran for both sport and commercial reasons. Greater Scaup are hunted with shotguns, because they must be shot on the fly. Hunting Greater Scaup is very challenging, as they can fly at up to121 km/h (75 mph), which makes shooting them in flight very difficult. Greater Scaup are hunted from shorelines and in open water hunting blinds or layout boats, low-profile kayak-like boats that hunters lie inside. Hunters frequently use decoys to attract the birds, often arranged to simulate a raft of Greater Scaup and featuring an open area to attract the birds to land.

References

Notes

Bibliography

• Delin, Håkan (2001). Färgfotoguiden över alla Europas fåglar. Bonniers. ISBN 91-34-51940-8. {{cite book}}: Invalid |ref=harv (help)
• Ullman (maps), Magnus (1992). Fåglar i Europa. Wahlström & Widstrand. ISBN 91-46-17633-0.
• New Shorter Oxford English Dictionary. Oxford University Press. 1993. ISBN 0198612710. {{cite book}}: Invalid |ref=harv (help)

Further reading

• Splitting headaches? Recent taxonomic changes affecting the British and Western Palaearctic lists - Martin Collinson, British Birds vol 99 (June 2006), 306-323
• Madge, Steve (1988). Wildfowl: An Identification Guide to the Ducks, Geese and Swans of the World. London: Christopher Helm. ISBN 0-7470-2201-1. {{cite book}}: Unknown parameter |coauthor= ignored (|author= suggested) (help)

External links

• Cornell Lab of Ornithology: Greater Scaup
• USGS Patuxent Bird Identification InfoCenter: Greater Scaup
• South Dakota Birds and Birding: Greater Scaup