Extra-pair paternity and male badge size in the House Sparrow

Females of socially monogamous bird species frequently accept or solicit copulations with males other than their social mate. It has been proposed that in so doing females either gain direct benefits such as increased likelihood of fertilization in the event of their social mate being unable to provide sufficient sperm, or indirect (genetic) benefits for their offspring, e.g. 'good genes' from extra-pair partners of higher genetic quality than their own mate. Male ornaments such as elongated feathers and patches of coloured feathers are thought to act as visual cues to male quality. In this study we have used single-locus DNA profiling of two House Sparrow Passer domesticus populations to test the 'good genes' hypothesis prediction that males of low quality a ill be cuckolded most frequently. Both intra- and extra-pair mate choice is influenced by the size of the male's black bib which may be indicative of male quality. Contrary to the 'good genes' prediction, small-bibbed males were not cuckolded more frequently in either population. Furthermore, none of the measured breeding parameters or female characteristics correlated with the occurrence of cuckoldry.