I had a female Galah given to me who had plucked herself after they tried to introduce a mate to her after 10 years of being on her own. She pulled all her feathers from about the neck down. She still had flight feathers and tail but her belly was bare. Unfortunately she had damaged the feather shafts and a patch in her belly never grew back. She was ok if there was no member of the cockatoo family close to her but if you put a galah or a corella near her she would pluck again. It took years for her to cope with a too anywhere near her and she was such a lovely bird.
My thoughts are Merlin is jealous and that is causing his plucking. If he is tame try giving him more attention. Unfortunately about the only way to stop them is to use an Elizabethan Collar and they are not very attractive and do restrict the birds movements. It could be a case of the move and introducting 2 new birds. Unfortunately nothing helped with Billy as she had damaged the feather shafts in the middle of her belly and they were never going to grow back but she did eventually get used to other birds near her and even fell in love with a Corella. Unfortunately she passed away at the age of nearly 30 but she never had another bird in the cage with her but she and Wild One would kiss through their respective cages.
My thoughts are Merlin is jealous and that is causing his plucking. If he is tame try giving him more attention. Unfortunately about the only way to stop them is to use an Elizabethan Collar and they are not very attractive and do restrict the birds movements. It could be a case of the move and introducting 2 new birds. Unfortunately nothing helped with Billy as she had damaged the feather shafts in the middle of her belly and they were never going to grow back but she did eventually get used to other birds near her and even fell in love with a Corella. Unfortunately she passed away at the age of nearly 30 but she never had another bird in the cage with her but she and Wild One would kiss through their respective cages.