The type species of the genus Aythya was first identified in the 18th century in Lapland, Finland; roots of a prehistoric relative trace back to the Early Pleistocene.
In his ancient texts, Aristotle mentions an unidentified seabird that laid “two or three eggs in the rocks by the sea shore.” He called it aithuia—a name later given to a genus of diving ducks by 19th-century German Zoologist, Friedrich Boie upon renaming the greater scaup. Its species name marila comes from the Greek word for coal embers.
These highly social birds form rafts that number in the thousands, creating a spectacle that may have informed the common name scalp—the Scottish and Northern English word for shellfish bed.
Identifying the Greater Scaup
Known as the “bluebill” across North America, the greater scaup is the larger of the closely related lesser scaup. It is a mid-sized diving duck with yellow irises and a characteristic blue bill. The handsome drake has a black head with bottle-green iridescence visible in good lighting.
His gray back has pale vermiculated patterning. He has a cream-white belly and flanks, a black breast, and a short black tail. A white band along the flight feathers of each wing is visible during flight.
Females have rich brown plumage that becomes grayish during winter. Their bills are somewhat duller blue than the males with conspicuous white patches at the base. Juveniles have a similar plumage. Eclipse males may appear similar to females from afar—sans the white patches—distinguishable by the pale vermiculations on the back plumage. Both sexes have grey legs and webbed, grey feet.
Fun Fact: Occasionally, a hen will have similar colouration as the male with a black head and grey back, but still bears the telltale white facial markings.
The greater scaup may be easily mistaken for its lesser cousin. Subtle differences can be useful in telling them apart. Greater scaups have a slightly more rounded head shape and larger bill with a distinctive black nail at the tip.
Arctic Breeding and Coastal Winters
The only circumpolar species of the genus, greater scaups breed in the Palearctic and Nearctic realms of the Arctic Circle. Their summer breeding grounds encompass Alaska, Scandinavia, Siberia, Russia, and parts of northern Asia. The vast majority of greater scaup populations are migratory, but resident birds have established in the Aleutian Islands in Alaska, where they are found year-round.
The remaining northern populations migrate south for the winter, taking to coastlines and seashores across the Northern Hemisphere in the fall.
Habits and Habitat
Migrating flocks rest and forage on islands in the shallow waters of large lakes. The drake begins his courtship in the early spring with a soft whistle to attract hens en route to their northern breeding grounds. A monogamous pair forms for the season, following a complex courtship whereby the males gather in groups around a single female, jostling for her attention.
The hen responds by bobbing her head with an outstretched neck, moving her bill from side to side, while giving a raspy call. Once a pair is formed, the nest-making commences. The nest is a shallow scrape constructed by the hen and lined with her down. Greater scaup pairs next close to one another, forming a large colony. The greater scaup breeds in marshy lowland tundra, nesting amid floating rafts of emergent vegetation in shallow lakes and ponds.
Once the eggs are laid, the drake leaves the nest and joins other males as they molt their breeding plumage in the cover of a large lakeshore that can be near the breeding grounds or miles away.
The hen incubates her clutch of six to nine olive-brown eggs for up to twenty-eight days. Nestlings are precocious, covered in down, and are able to walk, swim, and feed themselves soon after hatching. But they remain dependent on the hen for protection and are only able to fly around forty days after hatching.
Toward the end of summer, the birds migrate south to spend their winters in coastal bays and estuaries in tight flocks that often include other diving duck species.
Diving Depths
Greater scaups are excellent divers, able to reach depths of twenty feet and remain submerged for up to a minute while scouring the lakebed for food. This minimises feeding competition with other ducks, enabling them to feed on a wide variety of molluscs, crustaceans, insects, as well as aquatic plants and seeds. They forage the muddy substrates, prying with their large bills for invertebrates, dredging them up to the surface, where they are swallowed whole.
Predators, Threats, and Conservation
The greater scaup has a number of predators from coyotes and owls, to skunks and raccoons. Eggs and ducklings are frequently nabbed by ravens, gulls, and even foxes, skulking around nesting sites. The species is also a popular game bird, hunted in North America and Europe.
Greater scaup populations have been in steady decline since the 1980s, facing a slew of anthropogenic threats from habitat degradation to climate change.
Birds often find themselves entangled in fishing nets, leading to a significant number of drownings each year. During winter, around eighty percent of the global population is concentrated in the heavily urbanised northern region of the Atlantic Flyway, where they are subjected to various human disturbances and environmental contaminants from oil, sewage, and run-off. In one study, high levels of heavy metals were evident in their tissues, eggs, and food sources.
Invasive species also pose a threat. In another study, it was found that hens that consumed invasive zebra mussels showed excessive selenium, leading to reproductive issues to the point of sterilisation in many females.
The species distribution in remote regions of the Arctic poses challenges for surveying and population management of greater scaup populations. The similarity with the more abundant lesser scaup further complicates this as the two species can be indistinguishable during aerial and ground surveys. Population counts are therefore obscured, which impacts regional waterfowl management and conservation efforts.
A banding program was implemented in recent decades to better track movement patterns, harvested numbers, and survival rates.
Despite plummeting population numbers, the species is classified as “least concern” according to the IUCN Red List, owing to the vast range and unreliable population data.
Final Thoughts
Like many waterfowl species, the greater scaup is vulnerable to the pollution of freshwater systems. The degradation of its habitat has drastically impacted populations. Tackling issues such as unsustainable pesticide use, excessive hunting, and climate change is essential for the long-term survival of the species, and many others occupying delicate freshwater ecosystems of the Northern Hemisphere.
The type species of the genus Aythya was first identified in the 18th century in Lapland, Finland; roots of a prehistoric relative trace back to the Early Pleistocene.
In his ancient texts, Aristotle mentions an unidentified seabird that laid “two or three eggs in the rocks by the sea shore.” He called it aithuia—a name later given to a genus of diving ducks by 19th-century German Zoologist, Friedrich Boie upon renaming the greater scaup. Its species name marila comes from the Greek word for charcoal embers.
These highly social birds form rafts that number in the thousands, creating a spectacle that may have informed the common name scalp—the Scottish and Northern English word for shellfish bed.
