Brood parasites include the cowbirds and many Old World cuckoos. Brood parasitism by cowbirds in North America or cuckoos in Eurasia is rare. Brood parasites include birds in different families such as cowbirds, whydahs, cuckoos, and black-headed ducks. Zygodactyly occurs in the parrots, woodpeckers (including flickers), cuckoos (including roadrunners), and some owls. The family Cuculidae includes cuckoos, roadrunners and anis. The family Cuculidae includes cuckoos, roadrunners, and anis. The Old World cuckoos are brood parasites. In this role they feed and care for subsequent broods and repel cuckoos or predators. Common redstarts are sometimes parasitized by common cuckoos. Hosts attack cuckoos more when they see neighbors mobbing cuckoos. The subfamily Cuculinae are the brood-parasitic cuckoos of the Old World. Some host birds can engage direct conflict with the intruding cuckoos. More visible nests were more likely to be selected by the common cuckoos. Aristotle was aware of the old tale that cuckoos turned into hawks in winter. They show a pattern of moult that differs from those of other parasitic cuckoos.