Authorities disagree on the timing and extent of migration. Breeders in northernmost California, and areas east of the Cascades and Sierra Nevada, depart for the winter, and population density declines noticeably elsewhere in the state, suggesting a general southward movement. Many individuals apparently migrate to the main wintering grounds in Mexico. Monogamous, solitary nester. Incubation 21-25 days.
Predation often causes heavy nest losses.
Minks and weasels sometimes kill incubating females. Wetland drainage has reduced populations in some areas. A waterfowl nesting study in the Sacramento Valley, California, 1955. Bellrose, F. C. 1976. Ducks, geese, and swans of North America.