Ah the Quaker Parrot, the scourge of the mid-west LOL many states have outlawed these birds because they are so hardy and breed so quickly, nesting in telephone poles and barns and creating a crop and public nuisance. Well, that is very uneducated of them. Yes these are hardy birds, but not generally a nuisance. So on to answering your question, (I love quackers by the way, easy to treat, lovely birds).
When a parrot first begins pulling or mutilating its feathers, the bird should immediately be taken to a qualified avian veterinarian for a complete work-up, including a CBC, to rule out any possible medical problems. There are medical causes of feather plucking and with the tests that are available, they are the easiest causes to determine. It just makes sense to go this route first.
Sometimes stress and changes in the home can bring on an episode of feather plucking. If you are experiencing stress or change in your life, be sure to take into consideration how it may be affecting your bird, and try to minimize it if possible. If the bird is being affected by something going on in your home, removing it to another home for a while can be a solution. When your situation stabilizes, then the bird can return.
Some birds may feather pluck if they do not get enough rest. Make sure your bird is getting 10 to 12 hours of sleep each night.
Seasonal lighting changes can contribute to feather grooming disorders, if your parrot does not have access to unfiltered sunlight (light coming through the windows in our homes is filtered), then you may want to install a full spectrum light on a timer for your bird.
Removing any source of salt in the diet can be helpful. When plucking is seasonal, you may want to look into changes to the diet that are made based on the seasonal availability of certain foods that you perhaps aren’t even aware of.
Remember that in many areas, lack of humidity is a seasonal problem so if your bird tends to pluck only at certain times of the year, this is a cause you might want to consider. Frequent showers or baths may help alleviate or prevent feather plucking.

