DO VARIABLE ENVIRONMENTS SIGNIFICANTLY INFLUENCE OPTIMAL REPRODUCTIVEEFFORT IN BIRDS

It is often assumed that environmental variability strongly influences the evolution of life-history strategies, principally by determining the optimal level of reproductive effort, and that differences in life histories between populations and species represent fundamental diffe rences in reproductive effort. In this paper, we use computer simulati ons and simple analytical approaches to demonstrate that even large am ounts of temporal variation in either fecundity or survival have relat ively little influence on optimal reproductive effort for generalized avian life histories. We suggest that demographic differences among po pulations or closely related species are not likely to result from dif ferences in the optimization of reproductive effort to environments wi th different levels of variability alone, but may reflect instead diff erences in average values of fecundity and survival.