Pair copulation frequency correlates with female reproductive performance in Tree Sparrows Passer montanus

In socially monogamous birds, males benefit from frequent copulations with their partner if this increases their paternity in the brood. By soliciting and accepting copulation attempts, female birds can control pair copulatio n frequencies. Engaging in copulations can be costly by taking up time and by increasing the risks of predation and pathogen transmission. Current hyp otheses propose that high pair-copulation frequencies may compensate for th ese costs by providing females with direct benefits that can result in high er reproductive success. In this study, I examine in a Tree Sparrow populat ion the prediction that high pair-copulation frequencies are associated wit h better female reproductive performance. The results show that clutch size s laid were positively correlated with the pair-copulation frequency. The l ength of the incubation period was negatively correlated and, as expected, the number of fledglings was positively correlated with pair-copulation fre quency. The results are consistent with current hypotheses for the evolutio n of frequent pair copulations and provide one of the few evidences for a p ositive relation between pair-copulation frequency and female reproductive performance. This study also suggests that within-pair copulation frequency could be an early expression of the pairs' reproductive ability and might signal their phenotypic quality.