You need to take your bird to see an avian vet to find out what is causing your bird to do this. It could be an allergy, infection or disease. It could also be a behavioral issue.
We do have a couple of articles on our Parrot Training page that you can read about helping plucking parrots.
Apr 11, 2009
Bird bleeding by: Judy Crumbly
It's best to get him to a avian vet ASAP as he could bleed to death. Birds don't have a whole lot of blood.