Females may not obtain indirect genetic benefits from extra-pair paternity in vinous-throated parrotbills, Paradoxornis webbianus

In birds, determining what females seek through extra-pair paternity (EPP) is fundamental in the understanding of variation in the incidence of EPP within and between species. I conducted genetic parentage analyses in vinous-throated parrotbills, Paradoxornis webbianus, a typical double-brooded passerine with a strong flock habit. In this species, it is known that the prevalence of EPP varies significantly between two egg-laying peaks; 95% of EPP occurred in the first peak. In the present study, I focused on whether or not females obtain genetic benefits through EPP and its relevance to the biased distribution of EPP between the two laying peaks. I found that females did not obtain ‘good genes’ so that extra-pair young were not better than within-pair young in terms of their body condition at the nestling stage or their survival rate to their first winter. I also found no significant effect of parental genetic similarity and local genetic diversity on the occurrence of EPP, and these genetic correlates were not related to the patchy distribution of EPP. Overall, this study concluded that female parrotbills may not pursue indirect benefits through EPP, and further study testing the possibility of direct benefits will be worthwhile.