Budgies mate by touching vents. The vent is the external opening of the cloaca, an orifice on the underside of the bird near the base of the tail. The male presses his vent against the female's vent briefly to expel sperm into it.
During mating, the breeding pair touches vents repeatedly, flying away and coming back to mate again over the course of the day. Before touching vents, the male puts on a mating display to encourage the female to mate with him. He chirps without ceasing, bobs his head and hops from perch to perch. If the female allows him to come closer, he hops from side to side on the same perch as the female and taps her beak.
A receptive female raises her tail and arches her back to facilitate vent touching. The male rubs his vent from side to side across the female's vent. In the wild, breeding patterns follow the rainy season because this is the time when food is most abundant. Wild budgies form monogamous pairs, but pet budgies in small colonies are promiscuous. Budgies are gregarious and breed more readily when they are gathered in small groups.