In order for budgies (or parakeets as they are often called) to mate, you must make sure you have a male and female. Unlike other bird species that can be difficult to sex, it is fairly easy to determine the sex of budgies unless they are very young. A male budgie will have a blue coloured cere (the area at the top of the beak), while the cere of a female will be a pale or a pinkish colour.
Courting and Bonding
Birds, like people, need time to adjust to each other. Budgies are usually very sociable birds and tend to get along with each other. While the pair may be leery of each other when first placed together, they should not fight or bicker with each other. As they adjust, the male will begin a courting ritual to attract the female to him. He will do a little dance for the female while ruffling his feathers, bobbing his head and singing to her. If the female accepts his courting attempts, you will soon notice them preening each other and the male feeding the female. This indicates that the pair has formed a bond that will last throughout their life together.
Budgies only mate when the female is ready. Until that point, the male spends his time courting her and any attempts on his part to mount her will be shunned. When she is ready to mate, the female will signal the male by crouching down on the perch and spreading her wings. The act of mating is somewhat different from other bird species in that it appears much more intimate. The male hops on the female's back and wraps one of his wings and tail around her as if cuddling her. This act helps stabilise the male and helps him to keep his balance. If he does fall off of the female during mating, he will simply remount her. The mating process may continue for awhile. The male may also feed the female while mating with her--many view this as kissing and loving each other. The male budgie will attempt to press his vent to the female's vent for fertilisation and will continue until the pair feels fertilisation has been achieved.