Scaup ducks are a type of diving duck commonly found across North America, known for their ability to submerge to forage for food. These medium-sized waterfowl belong to the genus Aythya. Their name may derive from “scaup” or “scalp,” a Scottish term for a shellfish bed, reflecting their winter feeding habits, or possibly from their mating call.
Identifying Scaup Ducks
Scaup ducks have a compact body shape. They are medium-sized, generally ranging from 15 to 22 inches in length with a wingspan between 27 and 33 inches. Both sexes possess a distinctive blue-gray bill with a small black “nail” at the tip and yellow eyes.
Male scaup display a dark head that can show an iridescent green or purple sheen, a black breast, and white flanks. Female scaup are primarily brown, featuring a white patch at the base of their bill. They dive to find food, often remaining underwater for extended periods.
Greater and Lesser Scaup Distinctions
Distinguishing between the Greater Scaup (Aythya marila) and the Lesser Scaup (Aythya affinis) can be challenging due to their similar appearances. The Greater Scaup is slightly larger, about 10% longer and 20% heavier than the Lesser Scaup.
A primary distinguishing feature is head shape: the Greater Scaup typically has a more rounded head, while the Lesser Scaup often exhibits a peaked or “notched” crown at the back of its head. Another reliable indicator is the white wing stripe visible in flight. The Greater Scaup’s white wing stripe extends further into the primary flight feathers, appearing longer, whereas the Lesser Scaup’s stripe is generally limited to the secondary feathers, covering only the inner half of the wing. In terms of bill characteristics, the Greater Scaup’s bill tends to be broader and wider, with a larger black nail at the tip compared to the Lesser Scaup.
Scaup Habitat and Diet
Scaup ducks exhibit distinct habitat preferences and migratory patterns. Greater Scaup breed across tundra regions in North America and Eurasia, including areas like Alaska, Siberia, and northern Canada. They primarily winter along coastal waters, large lakes, and estuaries, often found in saltwater environments.
Conversely, Lesser Scaup, predominantly a North American species, breed in inland freshwater wetlands across Canada and Alaska. They tend to winter on inland lakes, reservoirs, and coastal bays, showing a preference for freshwater or slightly brackish habitats.
Both species are diving ducks, and their diet primarily consists of aquatic invertebrates. They forage by diving underwater, consuming mollusks such as mussels and clams, aquatic insects, and crustaceans. Scaup also incorporate some plant material, like seeds, leaves, and stems of aquatic vegetation, into their diet. These ducks are known to form large flocks, sometimes numbering in the thousands, particularly during migration and in their wintering grounds.