Population-level Consequences of Conspecific Brood Parasitism in Birds and Insects

We explore the interrelationships between population dynamics and evolutionary dynamics in conspecific brood parasitism (dumping eggs in the nests of others) and show how behavioural dynamics alone can produce varying levels of conspecific brood parasitism in time and space. We challenge the widespread view that the relative fledging success of parasitic eggs must be high for parasitism to be a "successful" strategy. If professional parasites do not exist, this may have more to do with the deleterious effects of superparasitism than with the reduced success of parasitic eggs and we describe how the existence of facultative parasitism can immunize a population against invasion by professional parasites. Finally, we emphasise that optimality and evolutionary stable strategy (ESS) analyses of host and parasite strategies are only valid if the following condition is satisfied: the population dynamical equilibrium must both exist and be stable.