Great Northern Diver
From Wikipedia, the free encyclopedia
| Great Northern Diver or Common Loon | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
 |
||||||||||||||
| Conservation status | ||||||||||||||
| Scientific classification | ||||||||||||||
|
||||||||||||||
| Binomial name | ||||||||||||||
| Gavia immer (Brunnich, 1764) |
||||||||||||||
| Synonyms | ||||||||||||||
|
Gavia imber |
The Great Northern Diver, known in North America as the Common Loon (Gavia immer), is a large member of the loon, or diver, family of birds.
Adults can range from 61–100 cm (24–40 inches) in length with a 122–152 cm (4–5-foot) wingspan, slightly smaller than the similar White-billed Diver or "Yellow-billed Loon". The weight can vary from 1.6 to 8 kg (3.6 to 17.6 lbs). On average a Great Northern Diver is about 81 cm (32 inches) long, has a wingspan of 136 cm (54 inches), and weighs about 4.1 kg (9 lbs).
The Great Northern Diver breeds in Canada, parts of the northern United States, Greenland, and Alaska. There is a smaller population (ca. 3,000 pairs) in Iceland. On isolated occasions they have bred in the far north of Scotland. 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 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 black-blue and held horizontally. The bill colour 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 fish, flounder, sea trout, and herring.
The bird needs a long distance to gain momentum for take-off, and is ungainly on landing. Its clumsiness on land is due to the legs being positioned at the rear of the body: this is ideal for diving but not well-suited for walking. When the birds land on water, they skim along on their bellies to slow down, rather than on their feet, as these are set too far back. The loon swims gracefully on the surface, dives as well as any flying bird, and flies competently for hundreds of kilometers in migration. It flies with its neck outstretched, usually calling a particular tremolo that can be used to identify a flying loon.
Diver nests are usually placed on islands, where ground-based predators cannot normally access them. However, eggs and nestlings have been taken by gulls, corvids, raccoons, skunks, minks, foxes, snapping turtles and large fish. Adults are not regularly predated on, but have been taken by sea otters (when wintering) and bald eagles.[2] Ospreys have been observed harrassing divers, more likely out of kleptoparasitism than predation.[3] When approached by a predator of either its nest or itself, divers sometimes attack the predator by rushing at it and attempting to impale it through the abdomen or the back of the head or neck.
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.
This diver is well-known in Canada, appearing on the "loonie" coin and the previous series of $20 bill, and is the provincial bird of Ontario. Also, it is the state bird of Minnesota.
The voice and appearance of the Common Loon has made it prominent in several Native American tales. These include a story of a loon which created the world in a Chippewa story; a Micmac saga describes Kwee-moo, the loon who was a special messenger of Glooscap, the tribal hero; native tribes of British Columbia believed that an excess of calls from this bird predicted rain, and even brought it; and the tale of the loon’s necklace was handed down in many versions among Pacific Coast peoples. 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 can be related to Swedish immer and emmer, the grey or blackened ashes of a fire, referring to its dark plumage; or to Latin immergo, to immerse, and immersus, submerged.[4]
[edit] References
- ^ BirdLife International (2008). Gavia immer. 2008 IUCN Red List of Threatened Species. IUCN 2008. Retrieved on 2008-11-04.
- ^ http://animaldiversity.ummz.umich.edu/site/accounts/information/Gavia_immer.html
- ^ http://www.sbaa.ca/projects.asp?cn=303
- ^ Paul Johnsgard (1987) Diving Birds of North America. University of Nebraska Press. (Appendix 1)
- Appleby, R. H.; S. C. Madge and Killian Mullarney (1986). "Identification of divers in immature and winter plumages". British Birds 79 (8): 365–391.
The Great Northern Diver is featured in the Arthur Ransome novel Great Northern?
[edit] External links
 |
Wikimedia Commons has media related to: Great Northern Diver |
- — BTO BirdFacts — Great Northern Diver
- Loons
- Stamps: Common Loon
- Great Northern Diver videos on the Internet Bird Collection
- DigiMorph.org—CT scans of a Great Northern Diver skull
- Great Northern Diver on Animal Diversity Web
- USGS Information — Common Loon
- Cornell Lab of Ornithology — Common Loon Information
- South Dakota Birds — Common Loon Information and Photos
- Flicker Field Guide Birds of the World Photographs
