Delayed Dispersal and Reproduction as a Life-History Tactic in Cooperative Breeders: Fitness Calculations from Red-Cockaded Woodpeckers

Abstract

The evolution of delayed dispersal and reproduction in cooperative breeders can be viewed as selection between alternative life-history tactics: (1) stay-and-foray (SAF), in which individuals delay dispersal and reproduction and compete for breeding vacancies in the vicinity of the natal territory, and (2) depart-and-search (DAS), in which individuals disperse soon after fledging to wander in search of a breeding vacancy. Using demographic data collected from red-cockaded woodpeckers (Picoides borealis), we evaluated a demographic model of the evolution of delayed dispersal and reproduction based on selection between these tactics. Because males of this species exhibit both tactics regularly, we could estimate all model parameters directly. Our estimates provide empirical support for key assumptions of demographic models of the evolution of delayed dispersal and reproduction, such as a disparity in survival between those adopting SAF and those adopting DAS during the first year of life, a low rate of successful dispersal in those practicing DAS, and low reproductive success at early ages among breeders. We show, in a population in which the fate of dispersers could be documented, that the fitness of individuals delaying dispersal and reproduction can equal or exceed that of individuals attempting early reproduction, even without indirect fitness benefits due to helping behavior.