Most breed every year, although some forego breeding in years when food supply is poor. Modal clutch size 3, but some birds in poor condition lay 2 or even 1 egg. Annual and lifetime reproductive success . Others are shot or poisoned by anglers who regard gulls as competitors for fish. Tangle in nets, fishing lines result in significant mortality.
Most mortality occurs during breeding season.
Breeding-site fidelity and dispersal . Home range . Birds foraging in intertidal or close to breeding colony travel less than birds feeding offshore on fish or squid. Reyes and Pt. Historically, low juvenile overwinter survival, persecution on nesting colonies, and pesticide contamination in s.