Defense is mainly by the drake. After eggs hatch, the female defends a brood territory, usually at a different site than the nesting territory, driving off other females and killing, or driving away, their ducklings. Pair formation occurs mostly on wintering grounds. Precocial young tended by the female only. Breeds first at 2 yr.
Drake commonly attacks ducks of other species that enter the breeding territory.
A California Species of Special Concern. Ducks, geese, and swans of North America. Stackpole Books, Harrisburg, PA. 544pp. Cogswell, H. L. 1977. Water birds of California.