In most cases feather picking is caused by a complex combination of physical and behavioral causes. Since I believe a great deal of plucking starts for physical reasons, I encourage a full veterinarian work-up at the onset of the problem. The presumption should not be made that the problem is simply behavioral. However, even if picking starts for a purely physical reason, behavior complexities can continue the plucking beyond the resolution of the physical cause. The primary behavioral influence is attention paid to the bird when it is picking.
Parrots can be incredibly behavior.
A bird who starts plucking because of a simple insect bite may develop a habitual pattern if the owner pays attention to it every time it messes with its feathers. While picking birds certainly need nurturing and attention from their owners to feel secure, it is important not to give them that attention around their picking behavior. Gradual change by itself should not cause enough of a trauma to start a feather picking episode. However, parrots who have been overprotected and poorly socialized may not react well to any new situation, especially if it happens suddenly. If the change seriously threatens the bird's sense of security, phobic behavior may result in feather mutilation.