Extra-pair paternity in the Common Murre

Multi-locus DNA fingerprinting was used to estimate the frequency of extra- pair paternity in the Common Murre (Uria aalge), a colonial, sexually monom orphic seabird that breeds at very high densities and in which extra-pair c opulation is frequent. Common Murres produce a single chick. We detected 6 cases of extra-pair paternity in 77 families (7.8%). This value was higher than the proportion of successful extra-pair copulations (1.6%) estimated f rom behavioral data from an earlier study of the same population.