SERVEDIO, M.R.*; LANDE, R.; University of North Carolina, Chapel Hill; University of California, San Diego: Coevolution of an avian host and its brood parasite

We model the coevolution of host and cuckoo egg characters (termed �size� as a proxy for general appearance), host discrimination, and host and cuckoo population dynamics. Hosts use an evolving, comparative rule to decide whether to discard an unusual egg. We find a stable equilibrium for coexistence of the host and cuckoo where there is cuckoo egg mimicry, evolutionary displacement of the host egg away from the cuckoo egg phenotype, and host discrimination against unusual eggs. Both host discrimination and host egg displacement are fairly weak at the equilibrium. Cuckoo egg mimicry, although imperfect, usually evolves more extensively and quickly than the responses of the host. Our model provides evidence for both the evolutionary equilibrium and evolutionary lag hypotheses of host acceptance of parasitic eggs.