I have tried collars. Nico can just lift up the back part, and get to his tail feathers. He can also get to his neck feathers. I usually do this at night time when he is sleeping. A lot of feather plucking happens overnight. Some improvements were made on his tummy with the collar.
Nicoās vet was concerned too. The first appointment I had to walk in there, and tell her I adopted Nico, and I know nothing about him. I was of course warned of behavioral issues from the shelter (Nico didnāt act the same when I brought him home as he did at the shelter). Heās never shown aggression towards other birds. In fact he doesnāt care they exist. He likes things fairly quiet (heās not a fan of loud noises). Heās never entered my conures cages, or has gone anywhere near them. Usually he just follows me around, and wants outside.
What I did observe was toe tapping, wing flipping (not voluntary), falling off the perch, sneezing, off colored stool, not eating, under weight, missing feathers around the nostrils (also all over the body), lack of energy, atrophied muscle, over grown beak & nails (to the extent that the vet was taking off little millimeters while cutting his nails & was hitting the quick, extremely dried out skin, something being wrong with one of his wings and such. The vet looked even more perplexed when I explained to her that there were birds in worse shape than Nico at the shelter.
I was under the impression when I adopted Nico that this was a just to help him live out the rest of his life comfortably. I would describe Nico to be in a nursing home setting. Heāll never truly be āhealthyā. He just isnāt ready for hospice yet.