Patterns of extra-pair paternity in mountain chickadees

Extra-pair paternity (EPP) is common in chickadees and often attributed to the good genes hypothesis. Females generally seek dominant males, who are typically larger, older and sing at higher rates than subordinate males, as extra-pair sires. In other songbird species, habitat quality and urbanization have been found to influence EPP. Mountain chickadees commonly inhabit suburban habitat, and previous research on our population has shown urbanization may provide benefits to these adaptable songbirds. Here, we ask how individual condition and urbanization influence rates of EPP in mountain chickadees. Over three breeding seasons, we monitored mountain chickadee nests in urban and rural habitat, and determined parentage by genotyping adults and nestlings at six microsatellite loci. Extra-pair paternity is common in mountain chickadees, with extra-pair offspring (EPO) in 43.2% of nests and accounting for 17.9% of offspring. We found tenuous support for the good genes hypothesis with females tending to engage in EPCs with older males. However, we did not find an influence of male or female condition on the proportion of EPO in a nest. In addition, we did not find a significant effect of habitat on EPP rates, suggesting the impacts of urbanization on mountain chickadee reproduction may not extend to altering extra-pair behaviour.