A normal behavior that entails a bird shaking out all its feathers momentarily, then smoothing them down again. The term that falconers apply to this behavior is rousing, as in a bird rouses its feathers.
There appears to be multiple reasons for this behavior. It has been identified in association with a variety of stimuli, such as shaking out feathers subsequent to bathing; as a component of a happy greeting for someone or something the bird likes; or simple maintenance of proper feather alignment after a session of grooming.
Since this is a normal avian behavior, there is nothing that needs to be done (other than dust again if the bird is a high-powder species like a cockatoo or African grey).
Disclaimer: BirdChannel.com’s Bird Behavior Index is intended for educational purposes only. It is not meant to replace the expertise and experience of a professional veterinarian. Do not use the information presented here to make decisions about your bird’s health if you suspect your pet is sick. If your pet is showing signs of illness or you notice changes in your bird’s behavior, take your pet to the nearest veterinarian or an emergency pet clinic as soon as possible.