Do cuckoos imprint on hosts, micro-habitats, or nest sites? Parasitism preferences in the common cuckoo (Cuculus canorus)

Abstract

Diverse nest-building behaviors used for constructing delicate and diverse kinds of nests constitute one of the most impressive and typical traits for birds. However, some bird species do not possess nest-building behavior but lay eggs in nests of other species. Such obligate brood parasites account for only 1% of all bird species in the world, but their extraordinary behavior has resulted in numerous studies. Unlike nesting birds, brood parasites such as cuckoos need to find suitable nests for parasitism rather than suitable habitat for nesting. Previous studies hypothesized that cuckoos may achieve this by imprinting on the habitats or nest sites they have experienced, or on host species by whom they have been reared, or simply by natal philopatry. Here, we test for host recognition mechanisms in a coevolutionary system constituted by the common cuckoo (Cuculus canorus) and its two sympatric hosts Daurian redstart (Phoenicurus auroreus) and Verditer flycatcher (Eumyias thalassinus) that build open cup-shaped nests in similar nest sites. Redstarts are partial rejecters of cuckoo eggs and they are parasitized by cuckoos with a parasitism rate of 16.2%, while flycatchers accept cuckoo eggs but no survival of parasite chicks in its nests and also no single case of parasitism was detected. Our results are consistent with the host imprinting hypothesis that cuckoos choose suitable hosts for parasitism by preference for them during the nestling period. The unique system consisting of common cuckoos (Cuculus canorus) and their two potential redstart (Phoenicurus auroreus) and flycatcher hosts (Eumyias thalassinus) provided persuasive evidence to show that common cuckoos have a host preference rather than a nest site preference based on micro-habitat characteristics or just random nest site selection for locating host nests and choosing a suitable host species.