Known as the Long-tailed Duck in Europe, and until recently as the Oldsquaw in North America, this midsize sea duck is a true arctic species, breeding in tundra and taiga regions around the globe, as far as 80°N. After breeding, it migrates to cold and temperate-water coasts of North America, western Greenland, eastern Asia, and the Great Lakes. Individuals dive for food, to impressive depths not reached by other sea ducks (more than 60 meters), and have a broad diet of animal prey, focusing on food items that are locally abundant.
Unlike other waterfowl, Long-tailed Ducks have 3 plumages, instead of the normal 2 (Salomonsen 1949a). Additionally, the male Alternate plumage is worn only in winter, while the Basic plumage is acquired in spring and worn for the breeding season. The most distinctive feature, one that gives this species its name, is the 2 slim and elongated central tail feathers that stream behind the male. In summer, white feathers on the head of the male are replaced with black, and the male in breeding condition shows a bright-pink band around his bill. A distinctive feature of this bird is its call: nasal-sounding and audible from quite a distance along the coasts of its wintering grounds and on its tundra breeding grounds.
Despite its wide distribution, relatively little research has been devoted to this species. For behavior and reproductive ecology, studies by Alison (Alison 1973, Alison 1975a, Alison 1975b, Alison 1976, Alison 1977), Pehrsson (Pehrsson 1986), and Pehrsson and Nyström (Pehrsson and Nyström 1988) are comprehensive. Timing of migration and migration monitoring are described by Johnson and Richardson (Johnson and Richardson 1982), Woodby and Divoky (Woodby and Divoky 1982), and Alexander et al. (Alexander et al. 1988, Alexander et al. 1997). On the wintering grounds, feeding ecology has been studied by Peterson and Ellarson (Peterson and Ellarson 1977), Vermeer and Levings (Vermeer and Levings 1977), Johnson (Johnson 1984b), Sanger and Jones (Sanger and Jones 1984), Goudie and Ankney (Goudie and Ankney 1986), and Jamieson et al. (Jamieson et al. 2001) and nutrient reserve dynamics by Peterson and Ellarson (Peterson and Ellarson 1979) and Leafloor et al. (Leafloor et al. 1996). Contaminants have been examined by Peterson and Ellarson (Peterson and Ellarson 1975, Peterson and Ellarson 1976, Peterson and Ellarson 1978b).
The Long-tailed Duck is hunted throughout its range, by native hunters in the North and by recreational hunters in southern Canada and the northern United States. Obtaining population size and trend estimates for this species have proven difficult, as it usually winters in flocks of various sizes, is widely distributed, and can be far offshore. Available data for the west coast of North America suggest that this species is declining drastically. On the east coast, trends do not show evidence of declines, but estimates have been difficult to obtain.