Finches and other birds lay eggs, but there are some simple ways of knowing whether or not you can expect baby finches from your pair. You need to understand some basic facts about the mating and reproductive process of these fascinating birds.
Observe the behavior of your finches daily. Finches will begin to breed at around 11 weeks if allowed to, and you'll notice your male finches begin mating rituals to persuade the female to participate. Depending on the type of finch, the mating behavior can range from singing to elaborate fanning of the tail feathers.
Look for the mating act. The birds must join to pass the sperm from the male to the female. It may happen repeatedly over the course of several days, but the actual act only takes a couple of seconds. The male fertilizes the egg before it is fully formed inside the female.
Don't confuse egg-laying with reproduction. Female finches will often lay eggs even if a male finch is not kept in the cage. These eggs are best discarded in order to keep the cage clean. It's easy to tell if an egg isn't fertile: the finches won't incubate them. Often, the egg will be dumped onto the floor of the cage.
Keep plenty of nest-building materials in the cage. Male finches build nests after fertilization. If material is available, your male finch will build a nest for the fertile eggs. This will create a place for them to incubate the eggs. The distinction then becomes very clear for owners as to which eggs are fertile and which are not; the infertile eggs will lay on the floor, while the fertile eggs will be closely kept in the nest.