Small diving duck. Males 35 to 40 cm, 450 g; females 32 to 35 cm, 325 g. Compact with short neck; short and narrow gray bill. Strong sexual dimorphism both in size and color. Breeding males: head black, glossed green and purple, with large white patch from ear-coverts across nape; back black; white underparts; wings black with large white patch occupying most of secondaries and coverts. Females: mostly dark brown on head, back and wings; pale gray on underparts. They show a white ear patch and a smaller white wing patch than males. Males in eclipse plumage are essentially female-like but with larger white patches on the wings and face (Gauthier 1993).
For a comprehensive review of the conservation status, habitat use, and ecology of this and other Montana bird species, please see Marks et al. 2016, Birds of Montana.
Western Hemisphere Range
In the Bozeman area, normal migration periods are from March 20 to May 25 and September 1 to December 15, with peaks April 20 and November 10 (Skaar 1969).
Freshwater, permanent ponds with no outlet or only seasonal outflow, and small lakes. Large lakes are avoided except by molting flocks (Gauthier 1993). In general, the species is restricted to lakes and ponds (Skaar 1969).
Food is acquired through diving. Main foods taken are aquatic invertebrates (insects, crustaceans, mollusks). Will take some seeds (Gauthier 1993).
Near Fortine, numbers are believed to be increasing.
Has the habit of nesting in the holes of the Northern Flicker. Will also nest in boxes. Almost exclusively monogamous, it is one of the few ducks that often keeps the same mate for several years. Single brood. Clutch size varies 6 to 11 eggs (Gauthier 1993). Chicks less than 1 week old were recorded from June 11 to July 5 near Fortine. The average brood size was five.