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Great Northern Diver
last update: Mar 04, 2009 11:02 AM
Also known as the Common Loon
Latin name: Gavia immer
Longevity: unknown, but the oldest wild loon lived at least 9 years
Population: 580,000 individuals
Cites classified: Least Concern
Where found: Canada, parts of the northern United States, Greenland, and Alaska. There is a smaller population (ca. 3000 pairs) in Iceland.
Wingspan: 104-131 cm
Length: 66-91 cm
Weight: 2.5-6.1 kg
Mating/Breeding: Breeds on clear freshwater lakes with rocky shorelines surrounded by forest; also on subarctic tundra lakes. The female lays 2-4 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.
Eggs: Brown with dark splotches
Hibernation: Winters along both coasts and inland on large lakes from Alaska to southern Mexico, and Newfoundland to eastern Mexico. Also winters in Europe from Iceland to the Mediterranean
Aggressive?: When approached by a predator, loons sometimes attack the predator by rushing at it and attempting to impale it through the abdomen or the back of the head or neck.
Hunting Habits: catching its prey underwater, diving as deep as 200 feet (60 m)
Feed on: Freshwater diets consist of pike, perch, sunfish, trout, and bass; salt-water diets consist of rock fish, flounder, sea trout, and herring. Also includes other aquatic vertebrates and invertebrates
Predators/Threats: Adult loons have few known predators, but may be vulnerable to large marine mammals such as sea otters and large raptors, such as bald eagles and ospreys. Gulls, crows, ravens, bald eagles, raccoons, skunks, minks and weasels, snapping turtles and large fish are predators of loon eggs and chicks. When breeding, loons are threatened by fluctuating water levels (e.g. due to the building of dams), acidification of breeding lakes , heavy metal pollution (e.g. methylmercury contamination) and lead poisoning from ingested lead fishing weights. They are also highly sensitive to human disturbance such as shoreline development and human recreation, and may desert lakes after increases in human presence and activities. During the winter loons are highly vulnerable to coastal oil spills, especially in areas where large congregations form, and entanglement in monofilament fishing lines (used for sport fishing) and commercial fishing nets causes significant mortality at sea and on larger lakes. Loons are also susceptible to avian botulism so may be threatened by future outbreaks of the disease
Colour/Looks: 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 colour and angle distinguish this species from the similar White-billed Diver.
Interesting Trivia:
- Loons are water birds, only going ashore to mate and incubate eggs. Their legs are placed far back on their bodies, allowing efficient swimming but only awkward movement on land.
- The Common Loon is flightless for a few weeks after molting all of its wing feathers at the same time in midwinter.
