SINGLE-LOCUS DNA-FINGERPRINTING REVEALS THAT MALE REPRODUCTIVE SUCCESS INCREASES WITH AGE THROUGH EXTRA-PAIR PATERNITY IN THE HOUSE SPARROW (PASSER-DOMESTICUS)

Single-locus profiles produced with four cloned minisatellites were used to investigate the paternity of 44 house sparrow nestlings sired through extra-pair copulations. Comparison of the paternal alleles with a profile database of 144 candidate males resulted in 33 paternity assignments to 13 males. Both age and proximity were related to success in cuckoldry. Males achieving extra-pair paternity were usually breeding near to the cuckolded pair. Those at least two years old sired significantly more young through extra-pair matings, resulting in an average reproductive output 36% higher than that of yearlings. Whereas older males gained extra-pair fertilizations during their own breeding attempts, yearlings only achieved extra-pair success outside their own breeding cycle and did not significantly increase their own reproductive success. In contrast to other species in which extra-pair males are apparently chosen for their high quality, male sparrows siring extra-pair young were cuckolded at the same rate as other males.