Common Loon
For a few weeks in midwinter, Common Loons are completely flightless as they undergo a complete molt of their flight feathers. Most of these birds winter offshore along the Atlantic and Pacific shorelines.

Common Loons find small fish and other prey by peering below the surface or by probing into vegetation while swimming. They propel themselves with simultaneous kicks of large webbed feet and make dives up to 200 feet deep that last as long as several minutes. Most prey are swallowed underwater, but larger fish may be brought to the surface. With their legs placed far to the rear of the body, Common Loons are efficient swimmers but very awkward on land. They move on land either by shuffling or by sliding on their breast while thrusting rearward with their feet. They are unable to take flight from land, and even on water they must gain speed by running along the surface before lifting off.

Breeding takes place in lakes across Canada and along the northern border of the United States. A suitable lake is clear and sufficiently large to provide territories typically between 100 and 200 acres in size with a supply of fish; it also has islands suitable for nesting and is relatively free from human disturbance. The male's yodeling call can be heard up to 10 miles away and is used in territorial defense. Other calls, some resembling wolf howls or human moaning, are produced by both males and females. Most calls are heard in late evening. Pairs tend to return to the same territories each spring.
Common Loon Range Map

Common Loons place their nests on land adjacent to a steep slope with access to the water or on floating bog mats; the nests are made of aquatic vegetation piled up and shaped by the body. The lee sides of islands are preferred nesting localities. Common Loons generally lay two eggs. Nestlings leave the nest soon after hatching and ride on their parents' backs. The downy chicks are too buoyant to dive effectively, but after about three weeks they are chasing and occasionally catching small prey. Their parents feed them until eight weeks of age. Parents begin their southward migration first and young born that year follow about three weeks later.

Loons migrate in loose aggregations and roost together in flocks of as many as several hundred birds. Many first-year birds molt later than adults, and they may linger on the winter range during the breeding season. Winter habitats are selected both to provide adequate food sources and to avoid exposure to storms that would be a threat during the flightless period.

Habitat loss through lake shore development, increased recreational boating, acid rain degradation of lake waters and the consequent loss of fish, and heavy metal pollution all pose threats to loons and have been cited for declines in the northeastern United States. Populations in Canada appear to be stable or increasing.

Description: Common Loons are large birds, weighing about nine pounds with a wingspread of four feet. In the air they appear goose-like, but they have a humpbacked profile, shorter necks, and large feet that extend beyond the tail. They have stout, tapered bills. In the water they show a low profile and curved neck.

In breeding plumage the head and neck are glossy black with a green sheen. In the middle of the throat is a narrow horizontal patch of vertical white streaks, and on each side of the neck similar larger patches form a sort of broken collar. The black upperparts are thickly checkered with square white spots, with the largest spots on the scapulars and lower mantle. There are smaller spots on the black rump and flanks. The breast and belly are white, but the sides of the upper breast are black striped with white. The wings are dark with whitish streaks above and whitish axillaries below, and the tail is black. The eyes are brownish red and in the breeding season the bill is black.

In winter plumage the black of the forehead, crown, back of the neck, and upperparts is replaced with dark brown and the throat, cheeks, chin, and underparts are white. The prominent black-and-white-checkered pattern on the back of summer birds is replaced with a faint "ghost" pattern. The brown on the back of the neck extends to the sides of the neck where it merges with the white front of the throat in a jagged pattern. White spots above and in front of the eye form a partial eye ring. The bill becomes grayish with a black culmen and tip.

Common Loons in breeding plumage are easily separated from the smaller Red-throated (G. stellata), Pacific (G. pacifica) and Arctic loons (G. arctica) by plumage patterns and by bill size and shape, and from the closely related and nearly identical Yellow-billed Loon (G. adamsii) by bill color and shape. Winter identification is less straightforward as the plumages are very similar. Red-throated Loons show upturned bills, white speckling on the back, and white sides of the face and neck. In Pacific and Arctic loons, the border between the dark on the rear of the neck and the white on the front is a straight line. Arctic Loons show white flanks and most Pacific Loons show a slight dark necklace below the chin, and both lack the white eye ring of the Common Loon. Yellow-billed Loons have paler, less-patterned heads and necks and upturned bills with pale, not dark, culmens.


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