Relatedness and chick-feeding effort in the cooperatively breeding Arabianbabbler

Individual birds are expected to maximize their fitness by directing their chick-feeding effort only towards broods containing closely related nestlin gs. We tested this prediction using data from the cooperatively breeding Ar abian babbler, Turdoides squamiceps. Individual chick-feeding effort, in th e form of visit rates and load sizes delivered to the nest, was compared wi th three measures of relatedness: (1) band-sharing coefficients derived fro m multilocus minisatellite DNA fingerprints; (2) coefficients of relatednes s based upon pedigrees inferred from observed group histories; and (3) obse rved information on relatedness that was available to the birds themselves. There was little effect of any of the three measures of relatedness on ind ividual visit rates or load sizes delivered to the nest, both across indivi duals and within each group separately. In the majority of cases, we conclu de that individual birds did not have access to sufficient information conc erning their relatedness to the brood. As in certain other group-territoria l cooperative breeders, Arabian babblers may best direct their effort towar ds relatives by simply feeding any nestlings that appear on their territory . (C) 1999 The Association for the Study of Animal Behaviour.