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up atio itia er mm rib ere ed er ces uti thWhile the role that kin selection can play in the evolution of cooperative breeding is well established by a range of theoretical models (Hamilton 1964; Emlen 1991), empirical evidence of its importance is derived principally from studies showing that helpers are more likely to associate with and assist close kin (Emlen 1991). In many species, this occurs because helpers remain on their natal territory, return to it, or rejoin individuals with which they have been reared. Since all three strate-gies are likely to generate direct benefits to helpers as well as indirect ones, there is growing interest in whether resident helpers also adjust their level of investment in cooperative activities in relation to their degree of relatedness to the young. Results so far are mixed: while some studies have produced evidence supporting a posi-tive association between kinship and variation in the level of contributions to cooperative activities (Clark