For example, a bird flying away due to fear. On the other hand, bird communication can also be incredibly subtle. Before the bird flew there were most likely a number of body movements that indicated the bird was likely to fly. Behaviors such as feathers slicking back, darting looks, and crouching or springing behavior. Two of the most important tools for communication in birds are their eyes.
Birds telegraph much of what they are thinking by where, when, and how they look at things.
Paying close attention to eye behavior can give a trainer his or her best opportunity to understand what a bird may be thinking and, therefore, predict behavior to follow. As trainers, we try to communicate with birds through the application of Operant Conditioning. We utilize cues, bridges, positive reinforcement, negative reinforcement, etc. At least we believe that is how we are communicating. Quite probably birds are reading and reacting to our body language far more than we are reading and reacting to theirs.