Old, colourful male yellowhammers, Emberiza citrinella, benefit from extra-pair copulations

The frequency of extra-pair paternity was determined in broods of the yellowhammer using single-locus DNA fingerprinting. Of 32 analysed clutches, 69% contained at least one extra-pair young. Out of 123 nestlings, 37% were extra-pair sired young. The extra-pair male could be assigned to 23 (50%) nestlings. Successful extra-pair males were all at least 3 years old although both younger and older males suffered from extra-pair paternity. Extra-pair males were also significantly more colourful than pair males, but did not differ in other characters. Colour did not differ between males with or without extra-pair young. The frequency of extra-pair young was not related to breeding density and identified extra-pair males were not necessarily nearest neighbours, giving further evidence that extra-pair males are not chosen at random. Since females do not obtain anything but sperm from extra-pair males, the results suggest that females prefer older and more colourful males, contributing good or attractive genes, as indicated by their plumage. Consequently, old, colourful extra-pair males, and possibly females, are likely to benefit from extra-pair copulations. (C) 1996 The Association for the Study of Animal Behaviour.