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Largest of the loons; males weigh 4,000–5,800 g, females 4,025–6,400 g. Length (based on limited data): males 838–920 mm; females 774–831 mm. In summer, adult Yellow-billed Loon black above with extensive white spotting, white below; bill yellow or ivory. Winter and immature birds gray-brown. Only characteristic diagnostic in all plumages and ages is color of culmen (ridge of upper mandible). In Common Loon in winter plumage this ridge and about 5
mm on either side is black (in breeding plumage the entire bill is black), but in Yellow-billed Loon at least the distal half and usually distal two-thirds is whitish-yellow (Binford and Remsen 1974, Burn and Mather 1974).
Distribution/range – global and regional
Common breeder on Chukchi Peninsula and Taimyr Peninsula (Flint et al. 1984); rare to uncommon breeder on south island of Novaya Zemlya, Vaigach I., Yamal Peninsula, Gydanskiy Peninsula, shores of Laptev and E. Siberian Seas, Varanger Fjord (Norway) and Finland (Dement’ev and Gladkov 1968, Uspenskii 1969, Burn and Mather 1974, Flint et al. 1984, Godfrey 1986). In winter: apparently common along Pacific coast of Siberia (Dement’ev and Gladkov 1968); uncommon visitor to n. Japan (Brazil 1991); extremely rare in China (Cheng 1987); regular and common in Norway, especially Tromso (Collett 1894); rare but regular in Great Britain (Burn and Mather 1974); casual in continental Europe (Palmer 1962). Breeds in tundra of N America, Winters regularly in sparse numbers in nearshore marine waters from Kodiak I. (Forsell and Gould 1981) northeast to Prince William Sound (Isleib and Kessel 1973) and throughout se. Alaska (Dixon 1916, Bailey 1922, Gabrielson and Lincoln 1959) and British Columbia (Godfrey 1986).
Key habitats - seasonality
Nests in low-lying tundra regions, usually near the coast. Observed staging in migration on large freshwater lakes (Clarke 1940), rivers (Sage 1971), and nearshore marine waters (Bailey 1948, Lehnhausen and Quinlin 1981, Kessel 1989), but a large undetected movement may occur far offshore.
Biology – migration, life strategy, feeding, trophic relation, etc.
Primarily fish, some invertebrates and vegetation. Predation on adults not reported. Eggs and chicks subject to predation by Glaucous Gulls (North and Ryan 1988b). Other regular predators on eggs and chicks probably include jaegers (Stercorarius spp.), Common Ravens (Corvus corax), and arctic foxes (Alopex lagopus); possible limited predation in some areas by Snowy Owls (Nyctea scandiaca). Apparently reach maturity during third summer. Usually 2 eggs, occasionally 1 egg, per nesting attempt.
Population status – numbers and trends
No worldwide or continental estimates based on data. Estimates of 5,000–10,000 Yellow-billed Loons in Alaska (McIntyre 1991). No worldwide or continental information about trends.
Threats – natural and anthropogenic
Frequently drown in commercial, native subsistence and fishery research nets and traps (Collett 1894, Bailey 1922, Clarke 1940, Sutton 1963, Parmelee et al. 1967, Renaud et al. 1981).