Host species affects the growth rate of cuckoo (Cuculus canorus) chicks

The cuckoo (Cuculus canorus) is an obligate interspecific brood parasite. W hen about to lay an egg, the female must decide which nest to parasitise, A high-quality host species should be preferred, to enhance the possibility of producing a viable offspring, In this study, we investigated the effects of two closely related host species, the great reed warbler (Acrocephalus arundinaceus) and the reed warbler (A. scirpaceus) on the growth rate of cu ckoo nestlings. We found that cuckoo nestlings raised by the larger host sp ecies, the great reed warbler, grew significantly faster and became statist ically significantly larger at fledging than nestlings raised by the smalle r host, the reed warbler. Our results indicate a qualitative difference bet ween the two host species. The great reed warbler, considered to be the bes t host, was parasitised at a higher rate than the reed warbler.