Relative Importance of Parasitism by Chrysococcyx Cuckoos versus Conspecific Nest Parasitism in the Northern Masked Weaver Ploceus taeniopterus

In a 3-year study of the Northern Masked Weaver Ploceus taeniopterus in Kenya, I determined that fewer than 1% of the nests of this species had been parasitized by Chrysococcyx cuckoos. This rate of heterospecific parasitism is low when compared with the rate of parasitism by conspecifics, and I conclude that heterospecific nest parasitism has been a relatively unimportant factor in selecting for egg-color variability and egg-recognition ability in Ploceus weavers. I show that I could readily distinguish cuckoo eggs from weaver eggs, and I discuss the circumstances surrounding the six known or suspected cases of cuckoo parasitism that I detected.