The Yellow-billed Loon, known in Europe as the White-billed Diver, is a relatively rare bird nesting in arctic tundra regions of North America and Eurasia. This species was first described by G. R. Gray in 1859 (1), and named (Gavia adamsii) after the surgeon Dr. Edward Adams (who collected the first specimen) aboard the H.M.S. Enterprise on a voyage through Bering Strait. The Yellow-billed Loon is closely related and similar in appearance to the Common Loon (G. immer), but distinguished from the latter by bill shape and color. Further, the Yellow-billed Loon breeds generally north of the range of its more widespread relative, although the 2 species overlap on marine wintering grounds in the Pacific Northwest. Increasingly, however, vagrant Yellow-billed Loons have been recorded wintering well inland in North America, a phenomenon that likely stems in part from improved information on field identification of loons in Basic plumage.
During the breeding season, the Yellow-billed Loon occupies lakes and slow-moving rivers in low-lying tundra regions, entirely north of the tree-line, where it nests on islands and shorelines and forages for fish and invertebrates in nearby waters. Often arriving before lake ice has fully retreated, it sometimes feeds at ice edge, even diving beneath the ice in pursuit of prey. A strongly territorial species, each pair defends its lake (or portion thereof) against intruding members of its own species, other loons, and even diving ducks. Parents share incubation duties and feeding of the chicks, which are brooded onshore when very young.
Few ecological studies of this species have been conducted because of its remote breeding range and low population densities. Most of the information on this species comes from northern Alaska with relatively few studies conducted in western Alaska and the Canadian arctic. Sjölander and Ågren (2) described behaviors and calls during an 8-week study of renesting pairs at Alaktak, 80 km southeast of Barrow, Alaska. North and Ryan (3, 4, 5) studied Yellow-billed Loon habitat use, foraging ecology, reproductive success, nest-site characteristics, and breeding season chronology in the late 1980s on the Colville River Delta in northern Alaska. Recently, studies in northern Alaska examined territory retention (6, 7), foraging ecology (8), nest survival (9), nest site selection among loon species (10, 9), competition (11), exposure to disease (12, 13), impacts of disturbance (14, 15), and migration patterns (16, 17). Earlier general observations on breeding biology were made by Sutton (18), Parmelee et al. (19), and Sage (20). Most other information on Yellow-billed Loon breeding biology and distribution comes from accounts of early expeditions to the arctic (e.g., 21, 22, 23) or from studies of habitats and other species (e.g., 24, 25, 26).