why is my quaker parrot pulling his feathers

I have found one thing that seems to help and you aren't going to believe this:

Shoelaces.

The plastic sheaths covering the ends of shoelaces are called "aglets". I have found that parrots absolutely LOVE to work on these things. It keeps them occupied forever, and if you keep him stocked up with shoelaces, if might help. It gets a little expensive so you want to get the shorter ones as you are mainly concerned with just the aglets. Simply tie them onto his cage bars.a LOT of them.

One more important thing: Make sure he is getting enough sleep. Make his bedtime dark, quiet, uninterrupted and at least 10 hours in duration.

Also, consider getting him a play gym or parrot stand. Natural wood is best, and see that it has eye hooks so you can attach toys to it. Time out of his cage might be very helpful.

Just for some comfort: I took in a rescued and neglected 15 year-old Grey in August that was almost bald. She is well on her way to being fully recovered and is busily growing feathers back. She doesn't pluck at all any more. Part of her problem was that she simply wasn't getting enough sleep. With a solid 10 to 12 hours a night, a good diet, some trick training that boosts her self-confidence and a lot of time out of her cage every day, she is coming along great!

It can be done and I wish you luck..

I hope this gives you some insight into this behavioral issue