Hi,
The male and female work together to incubate the eggs and care for the chicks. The female can’t do it alone – it is too much work for her. When you have breeding birds, they can’t be pet birds that you handle, too. It creates confusion with the pair and can cause fighting. You mentioned the male has turned nasty and is biting, but all he is doing is protecting his mate and his nest. Breeding birds need privacy. If they feel threatened, this is one reason they might destroy the eggs. They should be in a quiet area where they do not have people around them other than to feed them. I’m not suggesting that you move them now, but try to give them their space. If you try to move them, they will abandon the nest. If the male leaves the next egg alone, then he probably threw out the other one because he felt the nest wasn’t safe.
There are other reasons for this behavior. Young males will do this to get the female to mate again. He is more interested in mating than caring for eggs. Unfortunately you do not know their ages, but it is best to wait until cockatiels are at least 2 years old before you set them up for breeding. If he continues to do this, the most likely reason is he is still too young, or he was set up to breed when he was too young before you bought him. If that is the case, this is a habit and it’s one you usually can’t break. The previous owners may have known this and known he was ruined for being a good breeding bird. If he throws out or breaks all of the eggs, then the best thing to do is remove the nest box and rest the pair for at least 6 months. After that, you can try returning the box. If the male breaks the eggs again, then this pair shouldn’t be bred again. He will continue this habit and it’s not healthy for the female to keep laying eggs for no reason. Each egg takes calcium and protein from her system and is physically draining to lay. So this pair may just be a non-breeding pair that is kept as pets.
Thank you for asking Lafeber,
Brenda