Begging call matching between a specialist brood parasite and its host: a comparative approach to detect coevolution

Studies of avian brood parasite systems have typically investigated the mimicry of host eggs by specialist parasites. Yet, several examples of similarity between host and parasite chick appearance or begging calls suggest that the escalation of host-parasite arms races may also lead to visual or vocal mimicry at the nestling stage. Despite this, there have been no large-scale comparative studies of begging calls to test whether the similarity of host and parasite is greater than predicted by chance or phylogenetic distance within a geographically distinct species assemblage. Using a survey of the begging calls of all native forest passerines in New Zealand, we show that the begging call of the host-specialist shining cuckoo (Chrysococcyx lucidus) is most similar to that of its grey warbler (Gerygone igata) host compared to any of the other species, and that this is unlikely to have occurred by chance. Randomization tests revealed that the incorporation of the shining cuckoo's begging calls into our species-set consistently reduced the phylogenetic signal within cluster trees based on begging call similarity. By contrast, the removal of the grey warbler calls did not reduce the phylogenetic signal in the begging call similarity trees. These two results support a scenario in which coevolution of begging calls has not taken place: the begging call of the host retains its phylogenetic signal, whereas that of the parasite has changed to match that of its host. (C) 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 208-216.