Avian reproductive disorders

The female reproductive tract of a bird consists of an ovary, oviduct and cloaca. Most female birds only have a functional left ovary and oviduct. While rudimentary remnants of the right ovary and oviduct may occasionally be observed, functionality is extremely rare. The kiwi (Apteryx spp.) is an exception, in which two functional ovaries are observed. The single left oviduct is positioned within the coelomic cavity to be able to receive oocytes from both ovaries (King and McLelland, 1984b). Paired ovaries and oviducts are reported commonly but irregularly in birds of prey (Kinsky, 1971). The oviduct consists of five parts: the infundibulum, magnum, isthmus, shell gland and vagina. The oviduct opens into the urodeum of the cloaca.

The male reproductive tract consists of paired testes and ductus deferens. In some species, males have a phallus, which may or may not be intromittent. The testes are symmetrical, paired and located internally, near the cranial end of the kidney. The ductus deferens carries spermatozoa from the epididymis to the urodeum of the cloaca. In passerine birds and budgerigars, the caudal end of the ductus deferens forms a convoluted ‘mass’ called the seminal glomus, observed as a cloacal promontory – a bulge, palpable adjacent to the vent. The seminal glomera are the main storage sites for sperm in these species (King and McLelland, 1984b). There are no accessory sex glands as there are in mammals. Most birds lack a phallus and mating occurs via ‘cloacal kissing’ (Videvall et al, 2018). Anseriformes, tinamous and ratites possess an intromittent phallus. Some birds, including domestic chickens and turkeys, possess a small non-intromittent phallus on the ventral lip of the vent (King and McLelland, 1984c).