Birds will wag their tails at the end of an activity. Although tail wagging is not a guarantee of a well bird, the absence of wagging in parrots is often an indication that the bird is stressed. These species also fluff their facial feathers and if the expression is peaceful the bird is probably just cute and content. While dogs beg attention by sitting up on their haunches, parrots will stare intently and flatten the body, lower the head, hold the wings out at the shoulders and quiver them. Cockatoos will also solicit attention by slowly scratching their own neck or head while adopting a soulful expression which clearly pleads for you to give them a scratch.
All birds preen their feathers.
A healthy and happy bird spends a great deal of its day grooming, running the feathers through the beak to spread the oils and to keep the feathers aligned. Birds which are preening are happy and feel secure. Absence of preening and dirty or untidy feathers indicate ill health. Parrots which flip both wings, fluff up their facial feathers and flare their tails are warning that they will become aggressive if you move any further into their personal space. Do not try to pet a bird while it is in this mood.