My Galah is a wicked little plucker. I've no idea how long he's been doing it because he plucks the area on his back where his wing coverts disguise the damage. His lower front is completely bald and I don't know whether that's because of actual plucking behaviour or because of the very large fatty tumours he has there. I suspect, as the tumours grew, he began plucking the overlying feathers, perhaps in an effort to make the tumours go away.
I never see Dominic plucking, so I don't know whether he's still doing it under cover as it were, or whether the follicle damage is so extensive that the feathers just aren't growing back. I've had Dom for nearly six months and in that time he's had a radical life change. Instead of being alone in a too-small cage with no toys, he now lives next-door to my Alexes, has tons of toys and daily out-of-cage time. In addition, he's gone from a sunflower-seed-only diet to a pellets and fresh veg diet. The fatty tumours are gradually shrinking and we hope to avoid surgery. If Dom's feathers grew back, that would just be the icing on the cake!
I try always to have chewy and foraging toys in Dom's cage. Also, I give him things like carrot chunks and half a banana on a chopstick to chew at. I figure if his beak is fully occupied, then it won't occur to him to chew. I also think the company is helpful. He doesn't get along with the Alexes (they scare him), but he does copy what they do. That's how he learned to play with toys.
Finally, I think the most helpful thing is to watch your bird and work out what interests and intrigues him. I gave Dom bells, for example, and he wasn't in the least interested. When he started munching on my address book, I gave him a hunk of phone book to chew on and that's been very successful.
Has your bird always plucked or is it a recent thing? What sorts of things do you do for him (I'm always on the lookout for new ideas!)? What has your vet said?
I wonder if there's anyone here on the forum who has successfully stopped a parrot from plucking. We'd all love to hear that story!
. She has stopped completely thank goodness, but I'm aware that its always going to be a potential problem. Diet change, daily baths, and constant monitoring is what did it for her. I didn't expect her to stop, I loved her as she was and was prepared to have a bird that would be potentially bald for life. But she stopped. 
