You are teaching me a lot! Went out tonight and looked at the back of his neck. Found some
Went out tonight to check on Kingy and now I understand! I looked carefully at the back of his neck and saw what you described. I could see his new feathers coming out and saw those sheaths that have not completely fallen off. There was something on You Tube about preening a parrot and that's what I tried to do. It actually worked! I got so excited! I will try again tomorrow night. But, until his new feathers come out, he will continue to itch?
New feather grow can be itchy - I'm glad you were to remove some of the sheaths.
It's very possible that parasites or even some neurological issues (like your vet mentioned) may be the cause of the scratching as well.
Keep us posted.