AbstractBreeding synchrony has been suggested as one factor that might explain the variation in frequency of extra-pair paternity, both between and within species. Reproductive synchrony might limit the opportunities for males to engage in extra-pair copulations (EPCs), because males face a trade-off with guarding their own fertile partner. Alternatively, breeding synchrony may promote extra-pair paternity, because of reduced male-male competition for EPCs or because of enhanced possibilities for females to assess male quality. In this study, I investigated the influence of synchrony on the occurrence of extra-pair paternity in the blue tit Parus caeruleus. Over four years, breeding synchrony and extra-pair paternity were positively related. Within a season, extra-pair paternity occurred independently of the timing of breeding. The fertile period of the extra-pair male's social mate and that of the extra-pair female often overlapped considerably. However, males who performed EPCs during the fertile period of their social mate were not more likely to lose paternity than males who performed EPCs after the fertile period of their mate. These data suggest that breeding synchrony has little influence on the occurrence of extra-pair paternity in the blue tit.
Extrapair paternity in the blue tit (Parus caeruleus) : female choice, male characteristics, and offspring quality