Here are some of the possible causes of non-medical plucking, most of them in the general category of stress. Following each cause are some possible solutions. The lack of humidity can cause their skin to become dry, flaky, and itchy. What starts as an attempt to scratch an itch can quickly evolve into full-blown feather plucking, and once it becomes a habit, it is very difficult to stop. The easiest way to supply extra humidity is to provide frequent baths and mist from a spray bottle.
Birds seem to avoid picking damp or wet feathers.
If this does not solve the problem, here are a few other suggestions. If one does not wish to bother with this source of humidity, a handy spray bottle or a clothes drying rack in the bird room on which to dry the family's laundered towels works just as well. Otherwise, a sheet or a large towel can be wet and squeezed partially dry and placed on the rack. Aloe vera spray is quite effective in soothing and moisturizing itchy skin, thereby preventing plucking. Feathers that are damp and that taste of aloe do not seem to be nearly as appealing to a feather plucker.