What changes the behavior answer
Look at the whole picture. A quick fluff and shake is different from a bird sitting puffed up for long periods.
Normal fluffing
Birds may fluff briefly while relaxing, preening, getting ready to sleep, or adjusting body temperature in a safe room.
Worry signs
Long-lasting puffiness with low posture, closed eyes, tail bobbing, appetite change, fewer droppings, weakness, or unusual quiet should be treated as illness risk.
Check the room
Cold drafts, poor sleep, fear, or stress can change posture, but do not use room temperature as an excuse to ignore sickness signs.
Safe rule
If a fluffed bird also acts unwell, call an avian vet promptly.