Elsewhere, including coastal areas, rare and irregular in winter. Migrants occur outside breeding range in April, early May, and September, particularly in southern California deserts and coastal areas. Breeding season lasts from mid-April to late July. Usually nests in a large colony with nests fairly closely spaced. Incubation lasts 10-13 days.
Adults aggressively attack hawks, crows, and other large birds near territory.
Storms and changes in water level can be very destructive. Males may form flocks postbreeding, separate from females and young. Life histories of North American blackbirds, orioles, tanagers, and allies. Crase, F. T., and R. W. DeHaven. Current breeding status of the yellow-headed blackbird in California.