Evolutionary origins and persistence of infidelity in Malurus: the least faithful birds

Fairy-wrens (genus Malurus maintain territories year round, and breed cooperatively, with all members of the social group provisioning young. Despite living with several adult males, the breeding female typically cuckolds all of them, seeking fertilisations from extra-group males that provide no care to her offspring, instead caring for the young reared on their own territory. We trace the evolutionary origins and persistence of this...