Abstract
Recent models for the evolution of polygyny in territorial birds predict that a female should choose to mate polygynously only if her expected number of off-spring is equal to or greater than her expected number if she mated monogamously. A recent model by Weatherhead and Robertson (1979) suggests that polygynous females can, in fact, tolerate lower reproductive success relative to available monogamous breeding situations if their sons inherit from their fathers an enhanced tendency to mate polygynously. Weatherhead and Robertson's model contains several inconsistencies that lead to misleading numerical predictions. These problems are indicated and a new model is presented. The model supports Weatherhead and Robertson's qualitative expectations. It predicts that an increase in the adult sex ratio, the average harem size, the frequency of polygynous males, or the degree of father-son resemblance in pairing success will all increase the size of the initial reproductive loss that can eventually be recovered. Consideration of the effect of reproduction over subsequent generations indicates that there is a limit to the number of generations over which a polygynously mated female can recoup an initial reproductive loss. A method is suggested by which the model may be applied to field studies of natural populations. Finally, limitations on the value of nongenetical approaches in modeling the evolution of female choice are discussed.
Published Version
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