Extra-pair copulations in common murres I: a mate attraction strategy?

Abstract

AbstractWe investigated the behavioural context of pair (PCs) and extra-pair copulations (EPCs) in individually-marked socially-monogamous, long-lived seabirds, common murres (Uria aalge). Since forced EPCs have been documented for this species, we first examined which sex controls successful (cloacal contact achieved) copulation. The finding that all successful copulations required female cooperation and crouching suggested that benefits of successful EPCs accrue primarily to females. In a group of murres for which paternity analyses indicated no extra-pair paternity, behavioural observations over five breeding seasons showed that individual females engaged in EPCs primarily under two circumstances: (1) before they were reunited with their mates, and (2) when they were in the process of re-pairing. There was no such relationship between EPCs and re-pairing for males. Successful EPCs occurred with familiar neighboring males of apparent high quality, indicated by their high ledge attendance and prior reproductive success rates. Thus, EPCs may be used by females to attract potential high quality mates in situations where females are attempting to re-pair as a result of divorce or mate death.