During mating seasons, the cloacal openings of both male and female birds swell and stick out from their bodies. During copulation, they rub their swollen cloacas together. The male's sperm, which has been stored in his cloaca, is deposited into the female's cloaca, where it travels up the chamber and eventually fertilizes an egg.
"In most birds the male and female make contact with each other's cloaca, in what is termed a 'cloacal kiss.' Sperm is transferred, and the whole action takes place very quickly," McGowan said.
Though the process of avian insemination is similar to that of humans and other mammals, you won't be seeing a birdie Kama Sutra anytime soon: Birds typically have sex in only one position, according to Ornithology.com. And despite rumors to the contrary, birds don't have sex while in flight.
Usually, the male perches on top of the female, who moves her tail feathers to the side to expose her cloaca. Arching back, the male rubs his cloaca against hers, according to Birdspot.co.uk