DISSERTATION RESEARCH: Extra-pair behavior and female fitness in the dark-eyed junco (Junco hyemalis)

Indiana University, Bloomington IN

Investigators

Abstract

This project examines extra-pair mating in birds from the female perspective. The research asks whether females that mate with more than one male benefit directly, by producing more offspring than they would if they mated with just one male, or indirectly, by producing offspring of higher quality. Conclusions will be based on DNA samples collected over 18 years from more than 4000 individuals and on long-term records of population dynamics and reproductive success. The study species, the dark-eyed junco, is a socially monogamous songbird. Males and females form a long-term pair bond and jointly raise offspring, but ~25% of all offspring are sired by a male other than the socially bonded male. Extra-pair mating is easily understood from the male?s perspective; a male?s reproductive success will increase if he mates with multiple females. Less clear is why females participate in this behavior, and past research has not resolved the question. The duration and scope of this study provide a unique opportunity to examine the influence of mating patterns on lifetime reproductive success of females. Results will clarify the potential for sexual selection in a species with a complex mating system.