INCREASED OPPORTUNITIES FOR CUCKOLDRY MAY BE WHY DOMINANT MALE FAIRY-WRENS TOLERATE HELPERS

The highest known rates of extra-pair fertilization (76%) occur in the superb fairy-wren (Malurus cyaneus), a bird that lives in both breedi ng pairs and in cooperative groups where 2-5 males assist a single fem ale. Males living in groups are cuckolded more often than males in pai rs, apparently because females can rely on helpers as an alternative s ource of care, and so do not need to allow their mate fertilizations. It is therefore unclear why dominant males tolerate helpers. Here we s how that dominant males with helpers provide less parental care during the nestling period, and use this reduced workload to make extraterri torial forays which are used to court extra-group females. DNA fingerp rinting suggests that this increased display rate provides them with a n advantage in obtaining extra-group copulations. These data suggest t hat within-pair and extra-pair paternity will not always be positively correlated.