How to tell if plucking or preening?
Look at the area around the feather(s) that he was messing with. When they pluck, you can notice the feathers starting to separate, or the skin around it might be irritated. Also, notice how he reacts when you go near the area. If he is normally okay with you being there, and suddenly becomes defensive, he may be plucking. If he is a problem plucker, the patches may never grow new feathers. If he is preening himself, the feathers themselves should be fairly intact; they only destroy the feather casings. The most important thing to look at is the base of the the feather’s shaft. If he is plucking, the feathers may have white marks or dents on them. They may be almost broken. If he is not plucking, they should look fine. Hope this helps!