Parasite adaptations during the nestling and fledgling stages

Abstract

Young of altricial brood parasites are fully dependent on their foster parents for a considerable period of time before being able to survive on their own. Therefore, they are expected to exhibit traits that allow them to avoid host defences and manipulate host’s parental behaviour to their favour. Many morphological, physiological and behavioural traits have been proposed as adaptations for brood parasitism based on their apparent selective advantage for parasitic chicks. In this chapter, we describe and discuss these putative adaptations to examine, in the light of available evidence, whether or not those traits have evolved specifically to increase parasites’ fitness. We show that whereas some adaptations are well-supported and indisputable, other traits require a closer scrutiny taking into account the parasite’s evolutionary history before concluding that they are true adaptations for brood parasitism. We propose some future directions for research on key adaptations to parasitism and coevolutionary interactions between parasites and their hosts during the nestling and fledgling stages.