Great Northern Diver

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iGreat Northern Diver/Common Loon

Scientific classification

Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Gaviiformes
Family:	Gaviidae
Genus:	Gavia
Species:	G. immer

Binomial name

Gavia immer
(Brunnich, 1764)

Not shown is the eastern part of the wintering range, which encompasses lakes and coastal areas down to Central Europe.

The Great Northern Diver, known in North America as the Common Loon (Gavia immer [GAY-vee-ah IM-mer]), is a large member of the loon, or diver, family. Adults are typically 73–88 cm (28–36 inches) in length with a 122–148 cm wingspan, slightly smaller than the similar White-billed Diver. They weigh between 2.7 and 6.3 kg with a mean value around 4.1 kg.

The Great Northern Diver breeds in Canada, parts of the northern United States, Greenland, and Alaska. There is a smaller population (ca. 3000 pairs) in Iceland. The female lays 1 to 3 eggs on a hollowed-out mound of dirt and vegetation very close to water. Both parents build the [nest], sit on the egg or eggs, and feed the young.

This species winters on sea coasts or on large lakes over a much wider range in Northern Europe and the British Isles as well as in North America.

Breeding adults have a black head, white underparts, and a checkered black-and-white mantle. Non-breeding plumage is brownish, with the chin and foreneck white. The bill is grey or whitish and held horizontally. The bill color and angle distinguish this species from the similar White-billed Diver.

This species, like all divers, is a specialist fish-eater, catching its prey underwater, diving as deep as 200 feet (60 m). Freshwater diets consist of pike, perch, sunfish, trout and bass; salt water diets consist of rock cod, flounders, sea trout and herring. The bird is whimsical on takeoff and landing, and clumsy on the land due to the position of the legs at the rear of the body, ideal for diving but not well-suited for walking. Birds land on water skimming along on their bellies to slow down rather than their feet, as these are set too far back. It swims gracefully on the surface, dives as well as any flying bird, and flies competently for hundreds of miles in migration. It flies with its neck outstretched, usually calling a particular tremelo that can be used to identify a flying loon.

The tremolo call, sometimes referred to as "loon laughter", is an eerie wailing, a symbol of the Canadian wilderness, and often used as atmosphere in horror films. Native tribes of British Columbia believed that an excess of calls from this bird predicted rain, and even brought it.

These birds have disappeared from some lakes in eastern North America due to the effects of acid rain and pollution, as well as lead poisoning from fishing sinkers and mercury contamination from industrial waste. Artificial floating nesting platforms have been provided for loons in some lakes to reduce the impact of changing water levels due to dams and other human activities.

The Great Northern Diver is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.

Head of a Great Northern Diver

This diver is well-known in Canada, appearing on the "loonie" coin and $20 bill, and is the provincial bird of Ontario. Also, it is the state bird of Minnesota.

Folk names include big loon, black-billed loon, call-up-a-storm, ember-goose, greenhead, guinea duck, imber diver, ring-necked loon, and walloon.

Gavia is Latin for "sea smew" (although divers are not Smew). The specific meaning of immer either is:

related to Swedish immer and emmer, the gray or blackened ashes of a fire, referring to its dark plumage; or
Latin immergo, to immerse, and immersus, submerged.

[edit] References

BirdLife International (2004). Gavia immer. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 09 May 2006. Database entry includes justification for why this species is of least concern