Which of these is not a sign of avian FAS?

In the context of avian fear and stress responses, preening is typically considered a self-soothing behavior rather than a sign of Fear and Stress (FAS). Parrots and other birds often engage in preening to calm themselves when they are feeling anxious or uncomfortable. This behavior can indicate that the bird is attempting to cope with stress, rather than exhibiting signs of it.

On the other hand, leaning away, standing tall, and having feathers slicked tight against the body are all recognized behavioral indicators of stress or fear in birds. Leaning away can suggest that the bird is attempting to distance itself from a perceived threat, while standing tall can be a defensive posture indicating that the bird feels threatened. Additionally, slicking feathers tight to the body can be a sign of agitation or discomfort. Therefore, preening stands apart from these other behaviors as a more positive or neutral action, showcasing the bird's attempts to manage its fear rather than exhibiting the signs of it.