Northern Prairie Wildlife Research Center
HABITAT: Inhabits lakes and ponds larger than 2 acres in montane, tundra, and subtundra habitats. Prefers moderately alkaline lakes, 5 to 15 feet deep, with a dense growth of submerged aquatic vegetation such as pondweeds and widgeon grass, and bordered by dense stands of bulrushes. Winters on lakes and rivers, and in coastal estuaries and bays where rocky reefs and ledges in shallow water provide feeding grounds.
SPECIAL HABITAT REQUIREMENTS: Cavities in trees near open water.
NEST: Nests in natural cavities in trees and stumps, in abandoned flicker nest cavities enlarged by natural decay, pileated woodpecker holes, or nest boxes, preferably within 100 feet of water. Occasionally may nest up to a half mile from water. Nests in dead or dying Douglas-fir, aspen, cottonwoods, lodgepole pine, ponderosa pine, and less commonly scrub pine. If tree cavities are not available, nests in holes in the ground or in cavities in rock cliffs or under rocks.
FOOD: Dives and forages in open water to depths of 3 to 10 feet for its food, which is 78 percent animal material. Primarily consumes insect nymphs and larvae, and water boatmen; crustaceans, especially crayfish; and some fishes, blue mussels, pondweeds, and wild celery.
REFERENCES: Cottam 1939, Bellrose 1976, Johnsgard 1975b, Palmer 1976b, Terres 1980.