A Comparative Study of the Eyes of Some Falconiform and Passeriform Birds

Abstract

The results of a comparative study of the morphology of the eyes in two orders of birds are presented in this paper. The species studied each belong to a different family, possess different modes of life, obtain their food differently, nest in different situations, and spend most of their lives in different layers of separate ecological associations. Six species were examined for this study. The Passeriform birds are: the house sparrow, Passer domesticus, of the family Ploceidae; the mockingbird, Mimus polyglottos, representing the family Mimidae; the meadowlark, Sturnella magna, of the family Icteridae. The Falconiformes are: the turkey vulture, Cathartes aura, of the family Cathartidae; the sparrow hawk, Falco sparverius, representing the family Falconidae; and the red-tailed hawk, Buteo jamaicensis (_ B. borealis), of the family Accipitridae. A major difference in the life habits between the two orders might be pointed out. The species belonging to the order Falconiformes usually spot their food from a distance considerably greater than that of the passeriform species, and only the sparrow hawk need fear an attack from raptorial predators. Those species belonging to the order Passeriformes, however, have two primary uses for their eyes; first, searching for food usually from relatively much closer distances and second, keeping a constant lookout for predators.