Greater Scaup

Aythya marila

(c) Glen Tepke
  • Swans, Geese, Ducks
  • Anseriformes
  • Porron bastardo, Buixot
  • Fuligule milouinan
Widespread across the Northern Hemisphere, the Greater Scaup is known bymany names, including bluebill, blackhead, greyback, and shuffler."Scaup" may refer to the "scalps," or shellfish, that it eats, or to its call, "kaup! kaup!".This marine duck's heavy body, an advantage in diving, requires it to run over the water to become airborne. When flocks of Greater Scaup take flight, the water surface boils with their effort. The chaos of wings and rushing water can dazzle a predator--or a naturalist. One of Audubon's Common Birds in Decline, the Greater Scaup's numbers have declined 75 percent since 1967.
Fun Fact

During the winter, nearly 80% of Greater Scaup converge in the urbanized, northern portion of the Atlantic Flyway, where, unfortunately, they face shrinking and degraded habitat and pollution.

Donna Dewhurst, US Fish & Wildlife Service
Bird Sounds
© Lang Elliot, Nature Sound Studio

A wide variety of vocalizations during active courtship, otherwise pretty quiet.

Appearance Description
On average, the Greater Scaup is 18 inches long, and weighs 2.3 pounds, with a wingspan of 28 inches. This fairly large marine duck has several distinct plumages depending on age, sex, and time of year. From October to June, the drake presents a black head, chest, and rear parts, which frame white sides and a grayish back that shades darker toward the tail. This gray appearance is produced by fine, wavy bars of black and white rather than actual gray feathers. All adults have golden eyes and a blue bill, tipped with black. During the breeding season, dark brown colors the female's chest and head. A clean, bold white patch marks the female's face at the base of the bill. Her body is gray-brown above, with a darker tail. Both sexes have a large white patch in the upper wings and whitish under-wings.
Differences between the Greater and Lesser Scaup are subtle, requiring good conditions for observation. The Greater Scaup has a more rounded crown when relaxed, a lighter grey back, no barring in the sides of the breeding male, a longer white wing stripe in flight, and a heavier build.
Range Map
Courtesy Kenn Kaufman
Range Distribution
From Alaska's Seward Peninsula, the Greater Scaup breeds at scattered sites southeast across northern Canada. Significant numbers also breed along the east coast of Hudson Bay and on Canada's Ungava Peninsula. Greater Scaup winter along the Pacific coast from Alaska to Baja California, and along the Atlantic coast from Newfoundland to Florida, with most ducks ranging from Cape Cod to New Jersey. A significant population uses the Great Lakes until they freeze.
In Europe and Asia, the Greater Scaup breeds from Iceland through northern Russia and winters from the British Isles south and east through the inland seas and then along Asia's Pacific Coast.
A legend for the range map to the right can be found here.
The Greater Scaup frequents calm or slow-moving water, and is found on salt water more often than the Lesser Scaup. This scaup breeds on the large lakes and bays of the Arctic flatlands, especially the tundra. Smooth shorelines are generally avoided. Basic requirements include shallow water, aquatic vegetation for hiding ducklings and for foraging, and wind protection for ground nests. In winter, Greater Scaup prefer shallow saltwater such as bays, lagoons, large tidal pools, and slow moving estuaries. Some large freshwater lakes are also used where food is abundant.
The Greater Scaup's heavy body and fully webbed feet help it dive as deep as 20 feet for up to 60 seconds. In winter, feeding flocks can be very large. This scaup is omnivorous and shifts its diet to whatever foods are most abundant, including insects and their larva, seeds, the succulent parts of aquatic plants such as muskgrass, wild celery, and sea lettuce, small mussels, clams, snails, crustaceans, marine worms, and fish eggs. Over the last ten years, the invasive zebra mussel in the Great Lakes has become an important but potentially dangerous food source, since these filter feeders concentrate pollutants.
Before and during migration, Greater Scaup form monogamous pairs which appear to last only one season. Several males court a female with displays, terrestrial and aquatic chases, and vocalizations that include coughs and whistles. Males without a mate often challenge mated pairs. In thick vegetation near water, the female makes a scrape and fills it with grasses, in which 6 to 8 olive-brown eggs are then laid and covered with down. The male departs about halfway through the 23 to 28 days required for incubation. Females defend nests and young with distraction displays to ward off ravens, arctic foxes, and various gull species.

Within a day of hatching, the female Greater Scaup leads the downy chicks to water, where they begin to feed in the shallows near cover. The female departs for staging areas before the young can fly. When they are between 35 and 42 days old, the juvenile Greater Scaup join other young and adults to prepare for the fall migration.

Cold weather in fall and lengthening days in spring both stimulate migration. Small flocks of Greater Scaup sometimes travel together in large formations along traditional routes. Starting in early September and continuing through December, males migrate first, followed by juveniles mixed with females. In early March, mature Greater Scaup of both sexes migrate north, followed by the young, to arrive on the breeding grounds in May.
CBC Graph
Graph Legend
Annual Population Indices
  • 1,300,000
  • 506,000
  • 2 million 40 years ago
  • 75 percent since 1967
Population Status Trends
In 2006, combined estimates of Greater and Lesser Scaup set a record low. Because these species cannot be identified separately from aircraft, most surveys simply count "scaup." Overall, scaup have declined significantly over the last 25 years. Christmas Bird Count data confirm this trend, indicating steady losses since 1942 for Greater Scaup. Estimating breeding Greater Scaup numbers has proven difficult, and shifts in distribution, possibly away from warming tundra, complicate the picture. The U. S. Fish and Wildlife Service lists the Greater Scaup as a "Game Bird Below Desired Condition" and a "Conservation Management Concern." The state of New York now considers it a species of "Greatest Conservation Need".
An explanation of the Annual Indices graph displayed to the right can be found here.
Conservation Issues
Because both Greater and Lesser Scaup continue to decline for unknown reasons, conservationists, game bird managers, governments, and hunters are becoming concerned. The record low count in 2006 was 37% lower than the long-term average. Accurate, yearly counts that separate Greater and Lesser Scaup are vital for monitoring this species.
Pollution has a significant impact on local Greater Scaup populations. Since the 1980s, mercury (linked to emissions from coal burning power plants) and selenium (a mining byproduct) are concentrating in the tissues of this marine duck. As they feed on an increasing number of filter feeding zebra mussels, the scaup may be ingesting more pollutants. In Long Island Sound during the winter of 1996 to1997, Greater Scaup tested above the Food and Drug Administration's limits for PCBs in poultry. The damage to human health caused by these pollutants is well documented, but the effects on Greater Scaup are mostly unknown.
What You Can Do
Support efforts to lower mercury emissions that may poison waterfowl like the Greater Scaup, and share your concerns with your state and federal representatives.
Help provide for the protection of and research on Greater Scaup by purchasing a Federal Duck Stamp .
Conserve Wetlands
Support wetlands conservation programs such as the Clean Water Act, North American Wetlands Conservation Act (NAWCA), and Farm Bill conservation programs such as the the Wetlands Reserve Program (WRP), and “swampbuster” (the rule that restricts wetlands from being converted to agriculture). Encourage governments at all levels to enact and enforce wetlands protection and water quality laws and regulations.

Help Halt Global Warming
Back strong federal, state, and local legislation to cap greenhouse emissions, and spur alternative energy sources. Conserve energy at home and at work (

Stop Invasive Species
Work with county agricultural officials to help fight the spread of non-native annual grasses. Support strong federal, regional, state, and local regulations and research and management to combat non-native, invasive species.

Patrol Beaches
Join beach watches to look for oiled birds or other signs of coastal pollution. Lobby with local, state, and federal officials to maintain wildlife-friendly beaches and clean coastal waters.
More Information
Natural History References
Kaufman, Kenn. Lives of North American Birds. Houghton Mifflin Company, New York, 1996.
Kessel, B., D. A. Rocque, and J. S. Barclay. 2002. Greater Scaup (Aythya marila). In The Birds of North America, No. 650 (A. Poole and F. Gill, Eds.). The Birds of North America, Inc., Philadelphia, PA.
Sibley, David Allen. The Sibley Guide to Birds. Alfred A. Knopf, New York. 2000.
Conservation Status References
Badzinski S. And S. Petrie. "Diets of Lesser and Greater Scaup During Autumn and Spring on the Lower Great Lakes." Wildlife Society Bulletin 34:3 (October 2006) 664–674.
Kaufman, Kenn. Lives of North American Birds. Houghton Mifflin Company, New York, 1996.
Kessel, B., D. A. Rocque, and J. S. Barclay. 2002. Greater Scaup (Aythya marila). In The Birds of North America, No. 650 (A. Poole and F. Gill, Eds.). The Birds of North America, Inc., Philadelphia, PA.
Nichols, Ted. "2006-07 Migratory Bird Season Information and Population Status." August 10, 2006. New Jersey Department of Fish and Wildlife.
Sibley, David Allen. The Sibley Guide to Birds. Alfred A. Knopf, New York. 2000.