Responses of potential hosts of Asian cuckoos to experimental parasitism

Abstract

In the arms race between avian brood parasites and their hosts, several adaptations and counter‐adaptations have evolved. The most prominent host defence is rejection of parasitic eggs. We experimentally parasitized nests of 10 potential host species breeding in sympatry with four different cuckoo species in an area in Bangladesh using differently coloured model eggs to test host responses. In four species we introduced both mimetic and non‐mimetic eggs. Black DrongosDicrurus macrocercus, hosts of the Indian CuckooCuculus micropterus, rejected all model eggs. Common MynasAcridotheres tristisand Jungle BabblersTurdoides striataaccepted all eggs regardless of mimicry. These two species are parasitized by Asian KoelsEudynamys scolopaceus, Common Hawk‐cuckooHierococcyx variusand, in the case of Jungle Babblers, Jacobin CuckoosClamator jacobinus. Pied MynasGracupica contra, with no records of parasitism in our study area, also accepted all eggs regardless of mimicry. In the six remaining species, all of which lay spotted eggs, we introduced only non‐mimetic eggs. Black‐hooded OriolesOriolus xanthornusrejected all model eggs, even though we have found no records of natural parasitism. Long‐tailed ShrikesLanius schachand House CrowsCorvus splendens, hosts of Asian Koels, rejected 75 and 9.1% of model eggs, respectively. Large‐billed CrowsCorvus macrorhynchos, apparently not used as hosts in our study area, accepted all blue but rejected all brown model eggs. Oriental Magpie‐RobinsCopsychus saularisand Red‐vented BulbulsPycnonotus caferaccepted all non‐mimetic model eggs. In Black Drongos, Long‐tailed Shrikes and Black‐hooded Orioles, all model eggs were ejected within 24 h of introduction. The results show considerable variation in egg rejection rates among various species, providing baseline data for further investigation of co‐evolutionary interactions between brood parasites and hosts in this region.