Extrapair paternity is influenced by breeding synchrony and density in the common yellowthroat

Abstract

The effects of breeding synchrony and density on levels of extrapair paternity in birds are controversial. We used multilocus DNA fingerprinting and microsatellite analysis to examine the effects of breeding synchrony and density on levels of extrapair paternity in the common yellowthroat (Geothlypis trichas). As in many Neotropical migrants, breeding synchrony was greatest at the beginning of the breeding season. Levels of extrapair paternity were higher after the peak in synchrony, leading to an overall negative relationship between extrapair paternity and breeding synchrony. However, there was a significant interaction between breeding synchrony and density, as levels of extrapair paternity were higher only for males breeding when both synchrony and density were low. We discuss several possible explanations for this interaction, including lower quality males or territories in low density areas and greater demands on mate guarding among males with larger territories. Most studies have not considered simultaneously the effects of breeding synchrony and density on extrapair paternity. Our results suggest that ecological correlates of paternity may be revealed only after testing for interactions in multivariate analyses.