Feather 'barbering'? On another bird?

[Mooka]

Hi everyone! I'm new here (sorry if this post seem repetitive, I haven't really seen a post talking about it happening to another bird?)

But I have two green cheeks, Kiwi and Chai

In November last year I found out the Chai had been ripping Kiwi's back feathers, not pulling them out, just biting bits off, she looked awful... I've seen people calling this barbering?
I told him off every time I saw him do it again and he stopped, she molted almost all of the damaged feathers and she looked normal again.

Until today! I came home to find that it's happened again, pretty much all of Kiwi's back feathers are damaged again!

Does anyone know why Chai does this? and why he might only be doing it once a year? Is it a breeding season thing? (Living in Aus, seasons are opposite to northern hemisphere)

Is he just bored and wants more to chew on? (they have plenty of toys but he never has much interest in them, only the things he shouldn't chew)

If anyone has had experience with this, let me know! I want to prevent it happening again next time, I'm worried Kiwi can't keep warmth in with all her feathers damaged she also looks terrible

He's only done this to the feathers on her back, she can still fly just fine and he hasn't done it to himself

 

[Anansi]

Hello, and welcome to the Parrot Forums family!

It could very well be hormonal, or it could be the stress of living together in a single cage. Consider how much room an individual bird would have in the wild. If things got a little testy between one bird and another, one or the other of them would always have somewhere to go.

Honestly, the only way that you can prevent this from having again is to provide each of them with their own cages. Either that, or provide them with an aviary large enough for them to feel like they have enough space to stake out an area for their own.