A comparative study of the reproductive systems of four species of Iowa hawks shows that the right ovary may be entirely lacking or persistent to a degree which may be functional. The right oviduct is either absent or vestigial. An embryological examination of Cooper's hawk shows that there is little or no migration of the primordial germ cells from right to left, as has been reported for other species, notably the English sparrow, the red-winged blackbird and the chick - and correspondingly less asymmetry in the reproductive system. The Falconiformes on this basis are assumed to represent a phylogenetic step between the reptilian stem and the higher birds.
Proceedings of the Iowa Academy of Science
©1935 Iowa Academy of Science, Inc.
Stanley, Allan J.
"Embryology and Anatomy of Iowa Hawks with Special Reference to the Reproductive System,"
Proceedings of the Iowa Academy of Science, 42(1), 208-208.
Available at: https://scholarworks.uni.edu/pias/vol42/iss1/98