Begging call mimicry and formation of host-specific lineages in the shining bronze-cuckoo, Chalcites lucidus

Antagonistic coevolutionary interactions between avian brood parasites and their hosts can lead to selection for the discrimination of parasites by their host via visual or acoustic signals. Therefore, nestlings of some brood parasites may be under selection to evolve visual and vocal mimicry of host nestlings to avoid discrimination by host parents. Some brood parasites diversify into host-specific populations by mimicking visual features of the host offspring (either eggs or nestlings). However, whether a similar mechanism applies to the begging calls of their hosts remains unclear. In this study, we analysed the begging calls of three subspecies of the shining bronze-cuckoo, which present visual mimicry of three different host species (family Acanthizidae) that vary in their ability to discriminate parasite nestlings. We found that the begging calls of each cuckoo subspecies match the respective host more closely than any of the other cuckoo subspecies. Therefore, selection for coevolutionary diversification appears to overcome phylogenetic constraints on cuckoo begging call structure. The coevolutionary interactions in these parasite–host systems have promoted the selection for refined host mimicry by the cuckoo and the formation of geographically isolated evolutionary units across the range of the species.