How do you treat a bird who plucks its feathers?

Give it more attention or remove it from the environment that is causing it stress. There is a medicine or treatment available from a Vet. that may help it stop. I'm not sure of the name, something like Pluck no more but any Vet. that treats birds should know what it is. It may be as simple as making more time for the bird. I have 7 and it can be demanding at times giving them as much attention as they want.