Introductory Information
Most of the time, a hen is stimulated to lay her eggs because she mated with a male. Sometimes, however, a hen may be stimulated to lay eggs even if no successful mating took place. Occasionally, a hen will lay eggs even if no male is even present in her enclosure: she may pair off with another hen, or simply lay eggs without any stimulation from any mate at all. Of course fertile eggs will only result from a successful mating with a male, but the point is that sometimes hens will lay eggs even without the possibility of any of them being fertile.
That being stated, if you have a male-female pair of gouldians who has completed their nest and mated, you will most likely be seeing eggs arrive in the nest soon. Once a pair has copulated, a small percentage of sperm from the male's ejaculate is stored in special "sperm storage tubules" in the female's reproductive tract. She may store sperm there for up to about 16 days and release some of it as she ovulates. This helps to ensure that sperm is available to fertilize her ova when she is ready to lay her eggs. It also allows her to produce multiple fertile eggs days after the last mating took place. The important implication of this is realizing that a hen pulled from a cage with multiple males in it may be carrying the sperm of different cock birds for about two weeks (contrary to popular belief, even "monogamous" species will engage in extra-pair copulations). Therefore, if you have a specific mating pair in mind (Hen "X" with Cock "Y") and want to produce offspring from this pair alone, you will need to keep other cocks away from Hen "X" for at least a 16 days before introducing Cock "Y" to her for breeding purposes.