Brood Parasitism and Cooperative Breeding: Seeking an Evolutionary Link

Abstract

From an evolutionary point of view, cooperative breeding and brood parasitism seem to have little in common. In avian cooperative species, individuals help feed young that are not their offspring, whereas brood parasites exploit the parental behaviour of a host, thus avoiding the costs of raising their progeny. Recent evidence, however, uncovered an evolutionary link between the two systems. On the one hand, it has been shown theoretically and empirically that conspecific brood parasitism (CBP) and cooperative breeding can be extremes of a continuum of parental care, where kinship among interacting females and ecological constraints on independent reproduction shape individual decisions. On the other hand, cooperative breeding and interspecific brood parasitism (IBP) might co-evolve, because the benefits of extra-care may select for a preference of nests with helpers in parasites, whereas a defensive function of helpers against the parasites would promote cooperative breeding in hosts. According to this hypothesis, the richness of cooperative species and brood parasites worldwide shows striking similarities, and within the two major host spots (Australasia and sub-Saharan Africa), passerine species that host obligate brood parasites are more likely to breed cooperatively. Although we have just begun to unravel the link between cooperative breeding and brood parasitism, the results have already widened our perspective on the evolution of avian breeding systems. Future studies that aim at building this bridge should therefore be encouraged.