Frequent copulation as a method of paternity assurance in the northern fulmar

Male fulmars, Fulmarus glacialis, employ a mixed reproductive strategy, copulating frequently with their mates while also taking opportunities to inseminate other females by extra-pair copulation. This study combines a complete record of copulation behaviour with paternity determined by DNA finger-printing in order to establish whether extra-pair copulations result in extra-pair paternity and to investigate how the fertilizing male achieves paternity. Despite the regular occurrence of extra-pair copulation (2·4% of all copulations involved an extra-pair male), no extra-pair paternity was detected in the study population. The upper 95% confidence limit for the population as a whole was 4·6% extra-pair paternity. The fertilizing male in all cases achieved both the greatest number of copulations relative to any other male and the last copulation before egg laying. The possible mechanism of paternity attainment in this species is discussed.