Hi Jeremy,
It’s actually your responsibility to limit how often your pair breeds and lays eggs. In the wild, breeding season is once a year, and a pair will have two clutches at the very most. One clutch per year is more likely. The seasons then change and this triggers the end of nesting and breeding season. In captivity, the birds do not receive the environmental signals to stop breeding. And by leaving the nest in the cage, they think they should keep breeding and nesting. They do not need the nest except when they are breeding. The nest should always be removed as soon as the chicks leave it, or if a clutch is infertile. The pair should then be rested for several months. You should only allow 2 or 3 clutches per year for a finch pair, with several months rest in between, with no nest. They don’t sleep in a nest in the wild. This is just a misconception in captivity. When they are in the rest period, you can take steps to discourage egg laying. Don’t let the female sit in a food cup – if she tries to, replace it with smaller cups. Limit their light to 8-10 hours by covering the cage early each evening. Move the cage to a different place in the room once a week. Ideally have the cage in a busy place in the home. This mimics what they would do outside of breeding season in the wild, which is to move to different areas depending on where food can be found.
As to why they ate the eggs or had infertile eggs, diet is one thing you need to change. A seed diet is not adequate for them. They eat some seeds in the wild, but they also eat greens, insects and other foods which varies by the seasons. You need to change your pair to a nutritionally balanced diet, which would be a finch pellet or granule. A very small amount of seeds can be offered a few times a week. You can easily convert them by mixing the pellets with their seeds, and gradually reduce the seeds and increase the pellets until they are only eating the pellets. You should also offer dark leafy greens and chopped veggies. When it is time for them to breed again, they need an egg food. Cook an egg with the shell washed, crushed and cooked with the egg. Never give them raw egg shells. The hen needs the extra protein and calcium to form healthy eggs. You can leave the cuttle bone in the cage year round, but during breeding, you can shave some of it over the veggies or egg food or even with the pellets, if she is not using it. And just as you limited the light and moved the cage around during their rest, once you return the nest, you start offering the egg food, put the cage in a quiet, private location, and let them have longer hours of light by not covering the cage.
So for now, I would remove the nest and make the changes for them to be in resting mode. Work on converting their diet and feed the foods I suggested, except for the egg food. In a few months, replace the nest, start offering the egg food and give them a quiet, private place for their cage so they will be encouraged to breed and nest.
Thank you for asking Lafeber,
Brenda