Zygodactyl

A specialised arrangement of the feet in which the toes are arranged in pairs, with the second and third toes facing forward and the first and fourth toes facing backward. This adaptation helps birds climb and perch on tree trunks and other vertical surfaces. Several groups of birds have zygodactyl feet, including the parrots, the cuckoos and turacos, owls, toucans and the woodpeckers and their relatives