quaker parrot losing feathers around mouth

by randy lundgren
(plant city fl)

my quaker parrot of five years is losing the feathers around the right side of his beak. he seems to be rubbing them off on the cage which has caused a minor abrasion on his skin. he interacts with our parrakeets and cockatiels daily without incident, although two of the parakeets are always hanging aroud and he gats tired of them and gently chases them away which doesnt last long and thier back, not really bothering him, just sitting in his "comfort" zone. could they be his problem or is it more complicated