I would start off by removing the nest box and resting the pair from breeding for at least 6 months. Your birds have been way over bred, and you let them breed when they were much too young. Cockatiels will become sexually mature at much too young of an age in captivity. But they are not emotionally mature enough to be breeding. The males will only want to breed and not settle down to care for the eggs and chicks. And the female is at a much higher risk of becoming egg bound at a young age. The male should be at least 18 months old to breed, but most serious breeders begin them at 2 years old. The female should be at least 2 years old before you allow her to breed. So it sounds like your pair started at one year old, and sadly they have developed some bad habits which you may or may not be able to break. Also, in the wild, a pair will only breed one time per year, then the season changes and it is no longer suitable for breeding. They abandon their nest and do not nest again until the next year when breeding season begins. In captivity, we provide an ideal breeding environment all year. However, the birds should never be allowed to keep breeding over and over. A pair should be limited to two clutches per year, whether the eggs hatch or not. The nest box should be removed in between clutches and the pair rested for 6 months. Your pair is tired, the male never got a chance to grow up and they need to be rested. You might even want to separate them, and let both birds be pets again for at least 6 months. After that, you can put them back together and see if they do better. When they are set up for breeding with their nest box, you should not handle either bird or spend time with them or give them personal attention. This can cause confusion and can cause them to fight because they can’t decide if they want each other, or if they want to be with humans. If you set them back up in 6 months, and they still fight, I would separate the pair and not breed them again. Not all birds will be good breeders and not all pairs are compatible. The male may prefer to be a pet. Either way, it’s not good to allow the female to keep laying eggs. It is hard on her health – remember they were never intended to lay eggs more than once per year. But in captivity, some females will keep laying eggs until they die. So it is important to limit her egg laying by removing the nest box and making changes like limiting her days to 8-20 hours by covering the cage each evening, possibly removing the male, keeping the cage in a busy place in the house instead of giving her privacy, handling her if she is tame, and limiting the fresh foods you offer. Basically you reverse the perfect breeding conditions when it’s time for them to rest. Hopefully after a good rest, they will be ready to settle down and breed again. They will be a bit older and maybe the male will settle down.
Thank you for asking Lafeber,