How do birds reproduce?

When birds are ready to breed, their reproductive organs – the testes and ovaries – swell and produce the sperm and ova. Male birds store sperm in their cloaca until an opportunity to mate arises, and females will receive that sperm into their cloaca before it travels to fertilize their ova. read more

Some bird species, most notably several species of swans, geese and ducks, do not have cloacas, but instead male birds have an actual phallus (penis) that is inserted into the female during mating. read more

Birds reproduce sexually by mating and then depositing shelled eggs, which they incubate, hatch and rear. Birds produce sperm and egg cells just as mammals do, but most male birds lack a copulatory organ. read more

While male birds possess two testicles, the female birds of most species have only one ovary. Birds mate only during the spring and summer, when food is most plentiful, and as this period approaches, the size of the testicles and ovarian follicles both increase. read more