Physical Characteristics
About 28-36 inches (70-90 cm) long. This is a large, long-bodied waterfowl with a stout daggerlike bill and large feet. During the breeding season, both male and female have a black head with some iridescent green, black bill, checkered back, and a broken white necklace. During the winter, they are dark above and whitish below, with an irregular broken neck pattern (Peterson, 1990). The wings are narrow but powerful, tail feathers are very short and stiff, and the three front toes are webbed ( Leahy, 1982).
Habitat
Gavia immer is found on lakes surrounded by conifers, tundra ponds, open lakes, bays, and seas (Peterson, 1990).
Geographic Range
This species is found from western and central Alaska, northern Yukon, northwestern and southern Mackenzie, central Keewatin, northern Manitoba, northern Ontario, southern Baffin Island, Labrador and Newfoundland south to northwestern Montana, North Dakota, northern Iowa, northern Illinois, northern Indiana, northern Ohio, northern Pennsylvania, northern New York, southern New England, and Nova Scotia. Summers south to southern California, Sonora, Texas, and the Gulf Coast. Winters along the Pacific coast from the Aleutians south to Baja California and Sonora, and along the Atlantic and Gulf coasts from Newfoundland south to southern Florida and west to southern Texas (American Ornithologists' Union, 1983).
Diet
This carnivorous bird eats fish, crayfish, shrimp, leeches, and frogs (Perrins and Middleton, 1985). Aquatic insects and water plants are occasionally consumed. To swallow a large fish, the Common Loon will crush it in its bill in order to swallow it easily (Forbush and May, 1955).
Reproductive Characteristics
The nest is a bare scrape at the water's edge or, in marshes or shallow water, a mound of wet vegetation that can be added to if the water level rises (Leahy, 1982). Two eggs are typically laid, occasionally one or three. They are oval-shaped, medium to dark brown to olive, with few to many blackish spots or blotches. The incubation period is 24-29 days. The chicks are capable of waddling upright. The chicks are fed by both parents even though they are able to peck at and eat small invertebrates, black flies, and a variety of aquatic insects. Weaning occurs between the 8th and 11th weeks (Perrins and Middleton, 1985).
Remarks
The Common Loon is also known as Big Loon and Great Northern Diver (Forbush and May, 1955). The average loon dive is approximately 1 minute though, if necessary, they may stay submerged for up to 3 minutes (Ligon, 1961). The dive may go to a depth exceeding 200 feet (60 m). They are very awkward on land, so visit land only to nest (Leahy, 1982). These sight hunters are highly specialized final predators in the aquatic food web (Perrins and Middleton, 1985). During the summer the loons' voice has been described as falsetto wails, weird yodeling, maniacal quavering laughter, and at night as a tremulous ha-oo-oo; in flight as a barking kwuk . Winters find this bird quiet (Peterson, 1990).
American Ornithologists' Union. 1983. Check-list of North American birds, 6th ed. Allen Press, Lawrence, 877 pp.
Forbush, E. H., and J. B. May. 1955. A natural history of American birds of eastern and central North America. Bramhall House, New York, 552 pp.
Leahy, C. 1982. The birdwatcher's companion: an encyclopedic handbook of North American birdlife. Hill and Wang, New York, 917 pp.
Ligon, J. S. 1961. New Mexico birds and where to find them. The University of New Mexico Press, Albuquerque, 360 pp.
Perrins, C. M., and A. L. A. Middleton, eds. 1985. The encyclopedia of birds. Equinox, Ltd., Oxford, 447 pp.
Peterson, R.T. 1990. A field guide to western birds. Houghton Mifflin Company, Boston, 432 pp.
Mary Kirschenbaum, July 1996.
