Different traits affect gain of extrapair paternity and loss of paternity in the pied flycatcher, Ficedula hypoleuca

Extrapair paternity may create marked variation in the reproductive success of males and thus contribute to the evolution of sexually selected traits in socially monogamous mating systems. We examined the distribution of extrapair paternity in a passerine bird, the pied flycatcher, in relation to plumage coloration and male age. The frequency of extrapair paternity was found to be low in our study population in Southwest Finland (38 of 857 (4.4%) offspring in 25 of 191 (13%) broods). We were able to identify the sire for 53% of the extrapair young and in each case the extrapair sire was at least 2 years old. The probability of siring extrapair young was not associated with pigment-based brown-black dorsal plumage coloration, structural ultraviolet (UV) coloration or forehead patch size. The probability of being cuckolded, however, increased with decreasing UV chroma of the white wing patch. Our results thus indicate that there are multiple factors influencing when and with whom females engage in extrapair copulations. They also indicate that the male traits influencing the decision to cuckold the social mate are different from those used for choosing an extrapair mate.