Just wanted to introduce myself (hi) and mention that I was very pleased to find this group. I have a number of birds, including a Congo African Grey, a yellow-collared macaw, a Hahn's macaw, two budgies, and six Gouldian finches. (And the chickens would be insulted if I didn't mention them; however, they don't live in the house with me.)
My three bigger parrots have all been with me since weaning, and they are about ten years old each. I have never had a problem with feather picking, except that my YCM has a beak issue that doesn't allow him to preen correctly, so he has a tendency to snip feathers off as opposed to running them through his beak. As a result, my Hahn's typically looked pretty ratty, because my YCM grooms him.
When I moved from southern California to northern California, in 2003, however, my Hahn's started feather plucking about six months after we moved in. I am not sure what caused him to start, as we have moved before (three times) with no ill effects, and he has never had a tendency to pluck. I suspect part of the reason was that he is no longer in the main part of the house, so he gets less attention from humans, and the main source of lighting is full-spectrum, rather than natural daylight. I have all the birds on the first floor (the only part of the house that I can keep cool in the summer and that isn't carpeted), but the room they are in is a converted garage, so other than a pair of French doors, there are no windows. I have read, since starting to research his plucking, that artificial lighting can be a culprit.
After trying some other fixes, with negative results, I started experimenting with setting up foraging stations, and eventually ran into this group, which has been great. Fingers crossed, but as of this morning, my Hahn's has little pin feathers all over his chest and the tops of his wings (where he was formerly Butterball bare). I keep walking in holding my breath, expecting to see him plucked again, but have been pleasantly proven wrong thus far!
Any advice as to how to help a bird who is missing his upper beak (my YCM) forage would be greatly appreciated. All the foraging toys are meant for birds who can "hook" things out of holes, or who can tear up paper and wood, and he can't do any of these things. He can tear up wet paper towels, but that is about the limit of his ability.