Cuckoo (Cuculus canorus) Science Article 6
Egg discrimination is well documented in many hosts of avian brood parasites, but the proximate mechanisms of egg recognition and rejection decisions are poorly understood. Relevant in this respect is the observation that rejectors of parasite eggs often delay their response. This delay has implications for understanding mechanisms important for egg recognition and is the main focus of the present study. We investigated experimentally the relative effects of egg mimicry and eggshell strength of common cuckoo Cuculus canorus eggs on the delay in rejection in marsh warblers Acrocephalus palustris. In addition, by video recording host responses, we elucidate the proximate mechanisms behind the delayed rejections. Host nests were experimentally parasitized with 3 types of real eggs differing in mimicry and/or eggshell strength.
Anton Antonov, Bard G. Stokke, Arne Moksnes, and Eivin Roskaft, Behavioral Ecology Advance Access published November 15, 2007