For nesting, prefers large lakes with extensive areas of emergent vegetation. Yearlong, apparently circadian activity. Small numbers breed elsewhere in California, but most winterers migrate to breeding grounds in other western states and Canada. Monogamous, solitary nester, with strong parasitic tendencies. Some females lay eggs only in their own nest.
Some females apparently are completely parasitic.
Redhead nests occasionally are parasitized by other ducks. Other causes of nest failure include predation by skunks, raccoons, crows, magpies, gulls, and flooding. Food habits of canvasbacks, redheads, and lesser scaup in Manitoba. Bartonek, J. C., and J. J. Hickey. Selective feeding by juvenile diving ducks in summer.