THE EFFECT OF KINSHIP ON HELPING IN THE COOPERATIVE BREEDING SEYCHELLES WARBLER (ACROCEPHALUS-SECHELLENSIS)

It has previously been argued that the feeding of nestlings by non-par ental birds may simply bean unselected consequence of delayed dispersa l in cooperative breeding birds in which individuals follow simple rul es such as 'feed any begging mouth in my natal territory'. However, in the cooperative breeding Seychelles warblers (Acrocephalus sechellens is), helpers are more likely to help feed full siblings (both parents still alive) than half-siblings (one parent died), and do not help at all when the young are unrelated (both parents replaced). Helpers, hel ping both full siblings and half-siblings reduced their helping effort (food provisioning and period of helping) significantly when rearing young of lesser relatedness. These behaviours suggest that helping has been selected for in the context of promoting an individual's indirec t fitness, and that it is not simply a by-product of 'provisioning beh aviour'. The mechanism by which kin discrimination in helping is achie ved appears to be associative learning; birds more often became helper s at nests belonging to related individuals who fed them (as a parent or a helper) when they were nestlings than at nests of related breeder s who had not fed them in the nest.