Birds of this order are terrestrial birds. They very in length from 5 ½ to 27 inches. The tail if relatively long. The feet are known as grapplers, with two toes pointing forward and two to the rear. The outer back toe is reversible. These birds are found on all continents except Antarctica. The inhabit arid deserts, woodlands, and humid forests. Their plumage is loose-webbed. The young are altricial. About 45 species of Old World Cuckoos are brood parasites. That is, they place their eggs in the nests of other species of birds so that the parent(s) of the nest will care for and hatch the eggs.