Courtship occurs on breeding grounds in May or June, and eggs are laid beginning in June. Monogamous, solitary nesters. Clutch size usually 2 eggs, range 1-3. Incubation averages 29 days. Precocial young are tended by both parents.
Weasels sometimes kill chicks.
On wintering grounds, some mortality occurs from illegal shooting, oiling, and probably entanglement in fishing nets. Cogswell, H. L. 1977. Water birds of California. California Press, Berkeley. Garrett, K., and J. Dunn.