We need to fix a couple of things here. Remove the nest box and separate your cockatiels. At 9 months old they should NOT be allowed to breed. You need to wait until both birds are at least 2 years old to pair them up and allow them to breed. While they may be capable of breeding at this age, they are not ready. They still have some physical and emotional development to go through. If you ask a cockatiel breeder who breeds quality birds for show, they will tell you not to start your pairs until 2-3 years old. Young birds tend to develop bad habits that will ruin them for ever being good breeders. Young males usually are more interested in mating than settling down and caring for eggs. And both sexes are more likely to break or eat the eggs. Once they start this habit, you may as well give up on breeding them because they will not stop. A young hen is at a much higher risk of becoming egg bound and dying or having other physical complications from egg laying. She’s more likely to suffer a prolapse which would prevent her from ever breeding again and would be an expensive, chronic medical issue for you to deal with the rest of her life. It takes a lot of physical effort to develop and pass an egg, and she is not ready at this age to do this safely. There are some changes you should make to discourage any egg laying until she is old enough.
As for the lovebird, put a lock on the cage or get a cage that can contain him. Cockatiels and lovebirds have very different temperaments. Lovebirds are much more aggressive and can badly hurt or kill a cockatiel. Cockatiels are able to do the same to the lovebird if provoked. Once they are old enough to breed and you set them up, they will become territorial and attack the lovebird when he comes around. The only reason your cockatiels have not attacked the lovebird yet is because they are too young and obviously not ready to breed or they would be territorial. These birds are from different continents and are not intended to interact, so please do whatever is necessary to keep them apart before something tragic happens. I know you love your birds and want to do what is best for them, and sometimes that involve tough love.
You need to do all of these things to discourage egg laying. Keep in mind that to lay eggs, she needs longer daylight, warmer weather, abundant food, and a quiet, private environment. Your goal is to reverse these conditions.
Limit her light to 8-10 hours by covering the cage early each evening
Do not give her anything to use as a nest – no bird huts or tents, no box, bowl, etc. If she decides to sit in a food bowl, remove it and replace with smaller cups.
Do not give her anything to shred such as paper or cardboard.
Rearrange the toys in the cage frequently.
Move the cage to a different place in the room. Move the cage about once a week, or whenever she shows signs of nesting – settling on the cage floor for example. This disrupts her idea of having a stable place to lay eggs and raise chicks.
If you feed a lot of fresh foods, stop offering any for a couple of weeks, and then only offer them in small amounts about 2 or 3 times a week. You can resume normal feeding later when the birds aren’t being hormonal.
If she is let out of the cage, do not let her get in any dark cozy places and don’t give her free roam.
When you handle her, limit any petting to only her head and neck – do not pet her on the body. Only a bonded mate is allowed to groom the body. We can’t be a mate, so touching the body is off limits.
If there is no metal floor grate, then do not use any bedding or paper in the cage tray – leave it bare and clean it daily.
All of the above can apply to the pair, not just the hen.
Thank you for asking Lafeber,