This is a vague term requiring more explanation. If birds are shaking out their feathers, then they are rearranging them as a grooming function. Falconers say such birds are rousing their feathers, and parrot owners often call this fluffing the feathers. Feather rousing can also be a happiness behavior, as parrots such as African grey parrots often rouse their feathers and wag their tails when greeting a beloved friend. As post bathing shivering, a wet bird might be chilly. If ambient temperatures are warm, shaking might be a reflex that encourages the shaking out of down feathers to speed their drying. Depending on circumstances, shaking might also indicate a bird feeling stressed or anxious.
As a post-bathing behavior, nothing need be done. If shaking is associated with anxiety or stress, those problems need to be addressed.
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.