Factors determining a clutch size reduction in California gulls ( Larus californicus): a multi-hypothesis approach.

Abstract

Compared the breeding biologies of California gulls at Mono Lake and at Great Salt Lake, Utah, testing hypotheses to explain clutch size reduction: age structure, egg predation, bet-hedging, effort reallocation, most productive brood size, parental mortality, and pre-egg food limitation. The pre-egg food limitation hypothesis is best able to explain the clutch size reduction (modal size 2 rather than 3) at Mono Lake, although egg-removal experiments show that the resource limitation is relative and not absolute. Clutch size variation at each site need not be viewed as the result of fine-scaled evolutionary adjustment, although the general clutch size decision machinery is presumably molded by selection.-from Author