EXTRA-PAIR PATERNITY AND MALE CHARACTERISTICS IN THE PIED FLYCATCHER

The pied flycatcher (Ficedula hypoleuca) is sexually dichromatic with extreme variation in male plumage coloration. The benefit for males of having black plumage is controversial, and few studies have found evi dence for a sexual selection benefit of being black rather than brown. However, blacker males may be better able to achieve extra-pair ferti lizations (EPFs), which may be an important component of sexual select ion. We studied the role of EPFs in sexual selection in the pied flyca tcher by establishing a set-up where two males with different back col oration (blacker vs browner) bred simultaneously near each other. DNA fingerprinting analysis revealed that 11% of offspring resulted from E PFs, and that 22% of broods included extra-pair young (EPY) among 36 n ests containing 223 nestlings. We found no evidence that browner males suffered more often from EPFs than blacker males. There was no correl ation of male or female morphology or age with EPF frequency. However, breeding pairs with low genetic similarity had EPY in their nests sig nificantly more often. Thus we argue that females paired with genetica lly dissimilar males may try to avoid the effects of extreme outbreedi ng by seeking extra-pair copulations (EPCs). Alternatively, incompatib ility between genetically dissimilar mates may simply expose females t o more extra-pair copulations.