Embryology of the Gonads of the Marsh Hawk, Circus hudsonius

The gonads of Circus hudsonius are bilateral and nearly symmetrical organs throughout the life of the bird. The right and left ovaries are equal in size at all stages. The embryonic testes are likewise equal in size and shape, both possessing a conspicuous cortex. Some cortical elements of the right testis persist until the bird is at least four months of age, completely disappearing by the age of seven months. The cortex of the left testis occurs in small islets dispersed over the ventral surface of the organ. These cortical elements may persist slightly longer than those of the right side, but have also completely disappeared at the age of seven months