Copulatory organ of poultry

Morphological adaptation of the male’s cloaca serving to appose and introduce semen into the female’s urodeum; in the chicken and most birds, copulation is facilitated by an erectile papilla at the point where the deferent ducts open into the male urodeum; only the gander and drake have a developed erectile penis; on its surface runs a spiral semen groove that closes into a canal upon erection; a rudiment of the copulatory organ in day-old chicks is used for early sexing.