Lesser Scaup

Adults are 38–48 cm (15–19 in) long, 41.7–43 cm (16.4–16.9 in) on average. The species can weigh 454–1,089 g (1.001–2.401 lb); males weigh 820 g (1.81 lb) on average while females weigh noticeably less, at 730 g (1.61 lb) on average. Wing lengths (not wingspans) are about 7.5–7.9 in (19–20 cm) in males and 7.3–7.8 in (19–20 cm) in females. The tarsus is about 1.4–1.5 in (3.6–3.8 cm) long, and the bill is 1.4–1.7 in (3.6–4.3 cm). The wingspan is 68–78 cm (27–31 in). The adult males (drakes) in definitive basic (breeding) plumage have a black, iridescent head and a small tuft at the hindcrown, a black breast, a whitish-grey back, wings with darker vermiculations and black outer and greyish-brown inner primary remiges. The underparts are white with some olive vermiculations on the flanks, and the rectrices and tail coverts are black. Adult females (hens) have a white band at the base of the bill and often a lighter ear region, and are otherwise dark brown all over, shading to white on the mid-belly. Drakes in eclipse plumage look similar, but with a very dark head and breast, little or no white on the head and usually some greyish vermiculations on the wings. Immature birds resemble the adult females, but are duller and have hardly any white at the bill base. …

Their breeding habitats are inland lakes and arctic marsh ponds from Alaska through western Canada to western Montana; few breed east of James Bay and the Great Lakes. Notable breeding concentrations, with more than half a million birds at the height of the season, can be found in Alaska, in the woodlands of the McKenzie River valley and on the Old Crow Flats. These birds migrate south (mostly via the Central and Mississippi Flyways) when the young are fledged and return early spring, usually arriving on the breeding ground in May. Lesser scaup typically travel in flocks of 25–50 birds and winter mainly on lakes, rivers and sheltered coastal lagoons and bays between the US–Canada border and northern Colombia, including Central America, the West Indies and Bermuda. Wintering lesser scaup are typically found in freshwater or slightly brackish habitat and unlike greater scaup rarely are seen offshore when unfrozen freshwater habitat is available. They may even spend the winter on lakes in parks, as long as they are not harassed, and will occur even on smallish Caribbean islands such as Grand Cayman. Thousands winter each year on the Topolobampo lagoons in Mexico, and even in the southernmost major wintering location—Ciénaga Grande de Santa Marta in Colombia—hundreds of birds can be seen. In Central America, flocks are present from July on, but only really numerous after September. …

Lesser scaup forage mainly by sifting through the bottom mud, usually after diving and swimming underwater, occasionally by dabbling without diving. They mainly eat mollusks such as mussels and clams, as well as seeds and other parts of aquatic plants like sedges and bulrushes (Cyperaceae), "pondweeds", widgeon-grass (Ruppia cirrhosa), wild celery (Vallisneria americana) or wild rice (Zizania). In winter, but less so in summer, other aquatic animals—crustacean, insect and their larvae and small fishes—form an important part of their diet. It has been reported that both the lesser and the greater scaup have shifted their traditional migration routes to take advantage of the presence of the zebra mussel (Dreissena polymorpha) in Lake Erie, which was accidentally introduced in the 1980s and has multiplied enormously. This may pose a risk to these birds because zebra mussels are efficient filter feeders and so accumulate environmental contaminants rapidly. They nest in a sheltered location on the ground near water, usually among thick vegetation such as sedges and bulrushes, sometimes in small loose groups and not rarely next to colonies of gulls or terns; several females may deposit eggs in a single nest. The drakes court the hens in the winter quarters; pairs form shortly before and during the spring migration. …