Coevolutionary hypotheses (COEV) predict that parasitic birds become more specialized in host selection over time as more host species evolve defenses. A contrasting model, PHYLO, suggests that brood parasites exhibit a phylogenetic trajectory toward increasing generalization because there is a...

The evolutionary interactions between permanently social parasitic species and their hosts are of special interest because social parasites are not only closely dependent on, but are also closely related to, their hosts. The small European slavemaker Harpagoxenus sublaevis has evolved several...

Exploitation of hosts by brood parasitic cuckoos is expected to stimulate a coevolutionary arms race of adaptations and counteradaptations. However, some hosts have not evolved defenses against parasitism. One hypothesis to explain a lack of host defenses is that the life-history strategies of...