Parakeets can be colony bred, but a walk-in aviary is required. Give them no nest box and get rid of anything they try to use as a nest if you don't wish to breed them. To be safe, you should take the other pair out if the female begins to lay eggs on the cage floor. How Do Parakeets Mate

How are birds able to reproduce?

The egg is fertilized inside the female during internal fertilization, which is the method used by birds to procreate. Like reptiles, birds have a cloaca, or a single exit and entrance for sperm, eggs, and excrement. The female cloaca receives the male's sperm. The egg is fertilized by the sperm. How Do Parakeets Mate