Paternity and the Relatedness of Helpers in the Cooperatively Breeding Bell Miner

We used multi-locus DNA fingerprinting to determine the parentage of 13 broods of Bell Miner (Manorina melanophrys) nestlings. Despite very large contingents of male helpers attending individual nests and living in close proximity to breeding females, we found only one instance of extra-pair paternity in 24 nestlings. The genetic father of the extra-pair nestling was not among the males in our study population. The majority of helpers (67% of 52 cases) were close relatives (r > 0.25) of at least one parent of the brood being provisioned. Helpers were more often closely related to the male than the female parent. Only 17% of cases involved helpers that were apparently unrelated to either of the parents of the broods being aided. We conclude that Bell Miners do not mate promiscuously and that the majority of helpers are close relatives of the breeding pair. Cooperative breeding in Bell Miners seems to have evolved as a system of collateral kinship among the breeding birds and helpers.