Male phenotype predicts extra-pair paternity in pied flycatchers

Extra-pair paternity has the potential to increase male reproductive success and in turn the potential for sexual selection to act on male traits predicting extra pair mate success. There is large variation among European populations of pied flycatchers (Ficedula hypoleuca) in the extent to which male traits predict success in extra pair mating behaviour. In an Iberian population with a relatively high proportion of extra-pair young multiple male traits were involved in extra pair paternity success. Cuckolder males had larger tarsi and more attractive sex ornaments (blacker dorsal plumage and larger forehead patches) than the individuals they cuckolded, results not replicated in other populations. Previous studies in the species have shown that all traits associated with achieving success in extra pair paternity in our population are heritable and likely reliable indicators of male quality. Siring additional young was an advantageous strategy for males as it did not imply loss of paternity in their own nests. Our results, thus, suggest that this behaviour may enhance the evolution of male traits associated to success in extra-pair paternity in this population.