Extra-Pair Paternity in the European Starling: The Effect of Polygyny

We determined the frequency of extra-pair paternity and intraspecific brood parasitism in European Starlings (Sturnus vulgaris) by performing multilocus DNA fingerprinting on 22 complete families from a population in southern Sweden. Among 92 nestlings, we did not detect any successful intraspecific brood parasitism. This confirms observational data that successful intraspecific brood parasitism is rare in this population. We detected eight extra-pair young. Except for one case, where all (two) nestlings were fathered by another male than the one attending the nest, no more than one nestling in each nest was fathered by an extra-pair male. Although the degree of extra-pair paternity was higher in nests of secondary females than in those of primary and monogamous females, this difference was not significant. There was no relationship between a male's paternity with his primary and secondary female during the same reason. There was a tendency for males to loose paternity in the broods of secondary females when the fertile periods of his females overlapped considerably. We suggest that the relative ease by which female Starlings can be mate-guarded, the fact that mate-attraction and mate-guarding do not have to be exclusive activities and the high within pair copulation frequency in Starlings may keep the degree of extra-pair paternity low.