The way to tell male and female parakeets apart is to look at the spot above their beaks. The male will have a blue area and the female a pinkish spot. When the female is ready to start breeding, about the age of one year, the spot will turn brown. When the female is ready to accept the affection of the male, you will see them spending more time sitting next to each other. They will give each other "kisses" and the male may feed the female as a sign of affection. This means the couple has bonded, something that is necessary before they will be willing to mate.
During this time, normally early spring, it is important to make sure the pair are healthy. Feed them a variety of seeds and pellets and fresh fruits and vegetables. Also, provide a cuttlebone and a mineral block for the pair. This will provide the additional calcium that is required for healthy eggs. At this point, the female may begin to raise her tail to indicate to the male that she is receptive to his advances.
The male bird does not have a penis. He will rub the spot beneath his tail against the same spot on the female until he ejaculates. She will then use her beak to make sure the sperm reaches the right area. A female will lay eggs even if they are not fertilized, but the eggs will not hatch. This is much like when a chicken lays eggs that do not turn into chicks. However, once mating has occurred, it is highly likely that any eggs will be fertile and will result in baby parakeets.