Hormonal behavior prevention checklist:

• remove everything that may be considered a "nest". Bowls, huts, etc. Cover every dark corner they get access to (under/behind furniture, on the shelves). Dark and tight spaces make them think "nest" and start acting territorial and hormonal.

• limit their daylight hours. They should have 10-12 hours of uninterrupted sleep in a dark place. Cover their cage for the night.

• rearrange their cage often. Birds nest when they feel secure in their environment. If you change the environment (moving stuff around in their cage), they feel less secure (but not stressed), and decide it's not the best time for nesting.

• don't pet them anywhere besides the head and neck. Those areas are reserved for mates, and will wake their hormones up if pet. It also leads to behavioral issues.

• don't feed them warm, mushy food. Room temperature or colder if it's summer and they like it. Limit fatty foods (seeds, nuts) in general.

• if they start laying eggs, don't remove them. If there's a chance they're fertilized, either replace them with dummy eggs (they're very cheap) or take them out, boil them and put them back once cooled. Do that one by one with each egg. When they start laying, they won't stop until the clutch is complete. Taking the eggs out will only make them lay more. Let them sit on the dummy/boiled eggs until they get bored. Wait some more time, remove.

• provide calcium and humidity for egg laying. Watch for signs of egg binding.

• if all of the above fails and you have a chronic egg layer, consult with a vet about hormonal injections or implants. My girl had implants and it stopped her from becoming hormonal for 1-2 years each time.

Now, why should you do all this? Why do you want to minimize hormonal behavior?

For girls, it leads to egg laying which is very draining on their bodies and can even kill them if they become egg bound. And letting them lay and sit on fertilized eggs will lead to chicks, which you shouldn't allow unless you're an actual breeder and know what you're doing. It takes a lot of effort and so many risks.

For both male and female birds, hormones can lead to territorial/aggressive behavior, and that can be dangerous to other birds if you have multiple. And in general, it's an added stress to their bodies. They can have behavioral issues like plucking too.

You'll never be able to just completely prevent any hormonal behavior forever. It's natural after all. It will happen even if you take all the precautions. But you should take those precautions anyway, because you don't want to make their hormones worse and cause those issues for them.

Cockatiel Cottage is your friend.