Northern Prairie Wildlife Research Center
HABITAT: Inhabits lakes, ponds, shallow rivers, slow-flowing streams, floodplain forests and bogs, preferably with weedy margins, near or in woodlands with large cavity trees. Breeds in a range that generally coincides with the boreal coniferous forest. Winters on bays, estuaries, rivers, and inland as far north as open water and food are available.
SPECIAL HABITAT REQUIREMENTS: Large trees (minimum dbh of 20 inches) with cavities for nesting, near clear, cold, shallow water for feeding.
NEST: Nests in tree cavities near or in water, preferably open-top, bucket cavities, but also in old pileated woodpecker cavities, in hollow stumps, in natural cavities, or when cavities are not available, in abandoned buildings, cavities among rocks, and nest boxes. Sometimes may lay joint clutches when cavities are scarce. Prefers nest tree entrances that are 6 to 40 feet above ground or water. Accepts nest boxes that are 9 by 9 by 24 inches in size, with an elliptical entrance 3 1/2 by 4 1/2 inches.
FOOD: Prefers to dive for food in water 3 to 12 feet deep. Consumes animal food, as 75 percent of the diet, including crabs, crayfish, mussels, snails, insects, and some fishes. Also eats seeds, tubers, and leafy parts of pondweeds; seeds of pond lilies and bulrushes; and wild celery.
REFERENCES: Carter 1958, Cottam 1939, DeGraff et al. 1980, Johnsgard 1975b, Palmer 1976b, Thomas et al. 1979.