Anti-brood Parasite Defences: The Role of Individual and Social Learning

In this chapter, we consider the ways in which learning is involved in the antibroodparasitism defences that hosts deploy across the nesting cycle. Broodparasitism varies in space and through time, and hosts have accordingly evolvedplastic defences that can be tuned to local conditions. Hosts can achieve theirdefence plasticity by individual and social learning, as well as by experienceindependentmechanisms. While these mechanisms can profoundly affect thecoevolutionary dynamics between hosts and their brood parasites, our understandingof how they feature across the host nesting cycle is far from complete.Hosts can actively defend themselves against brood parasitism via a variety ofbehaviours, including nest defence, egg discrimination and chick discrimination.Such anti-brood parasite defences rely on the host’s ability to recognise and thendefend against the parasitic threat, and there is good evidence that both thesecomponents of discrimination can be influenced by learning. To date, mostresearch has focused on the function of learning in nest defence, but the learningmechanisms underlying egg discrimination are much better understood; anddespite some notable exceptions, the role of learning in chick discriminationremains largely unexplored. An important challenge now is to understand theobserved plasticity of anti-brood parasite defences in the context of environmentalheterogeneity and specifically in terms of variation in the presence, detectionand reliability of parasitism cues.