Animalia Life

Gavia immer
TAXONOMY
Colymbus immer Brьnnich, 1764, Faeroes. Monotypic.
OTHER COMMON NAMES
English: Great northern diver; French: Plongeon huard, Plongeon Imbrin; German: Eistaucher; Spanish: Colimbo grande, Colimbo Comun.
PHYSICAL CHARACTERISTICS
26.0–35.8 in (66–91cm); 5.5–13.4 lb (2.5–6.1 kg). Very similar to the yellow-billed loon in all plumages. In alternate plumage, black upperparts with white checkering and spotting, black neck with white stripping, and black head. Underparts are white. Juvenal, second alternate, and winter plumages similar, dark gray brown upperparts, head, and nape; white underparts and throat. Bill is straight and black in alternate and dark gray with a black culmen in other plumages.
DISTRIBUTION
Breeds throughout Alaska, Canada, northern New England, northern Midwest, and parts of Greenland and Iceland. Winters in Pacific Ocean from southern Alaska to Baja California, on Atlantic Ocean from Newfoundland to Mexico, also Europe and Iceland. Migrates over land and down coasts; stages on larger lakes. Many non-breeders summer in winter range.
HABITAT
Breeds in clear, oligotrophic, forested lakes and large tundra ponds. Winters mainly on coast within 62 mi (100 km) of shore, occasionally on large inland lakes and rivers.
BEHAVIOR
Found in pairs on breeding grounds, singly or in loose flocks during migration and winter. Requires 100–650 ft (30–200 m) to take off, limiting common loons to large lakes. Extremely territorial on breeding grounds—other loons and waterbirds are chased off. Yodel call, a series of repeated two-note phrases, is recognizable to individuals and used to defend territories.
FEEDING ECOLOGY AND DIET
Feed mainly on fish and invertebrates; vegetation occasionally taken. Crayfish are a common food when fish are scarce.
REPRODUCTIVE BIOLOGY
Nests farther south than other loons, from May to October. Little is known about pair formation. Nest is made of vegetation in about a week, on land at the edge of a lake. Incubation 27–30 days. Young leave nest in one day, but may return for brooding. Young able to fly in 11 weeks. Predators include gulls (Larus), ravens and crows (Corvus), pike (Esox), and raccoons, weasels, and skunks (Carnivora).
CONSERVATION STATUS
Populations are stable. Not listed on IUCN Red List of Threatened Birds, but is listed as threatened or of special concern in several northeast states. Acidification of lakes, heavy metal contamination, and human encroachment threaten populations in southern range.
SIGNIFICANCE TO HUMANS
Inuit hunt 4,600 loons (of all species) per year for subsistence. Many Native American tribes have stories about common loons. Many loon conservation groups have also been formed to protect common loons in their southern range.

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