Feather destructive behaviour
Plucking, chewing feather shafts, barbering the edges or self-mutilating skin. Medical causes are found in a large share of cases and must be excluded before it is treated as psychological.
Going quiet, or screaming in a new way
A bird that stops vocalising has usually withdrawn. Persistent contact screaming often means it is calling for a flock that never answers.
Loss of interest in food, toys and people
Refusing a favourite food, ignoring a toy that was played with daily, or no longer coming to the cage door are all meaningful changes in an animal of routine.
Sleeping through the day
Daytime lethargy in a bird with adequate night-time darkness is not restfulness. It is one of the most reliable signals that something is wrong.
Repetitive, purposeless movement
Pacing a set route along the perch, spinning, head swinging, or over-preening one spot. Stereotypies develop where an animal has too little to do and no control over its environment.
New aggression or fearfulness
Biting, lunging or refusing to step up from a bird that previously did so willingly is a change worth taking seriously rather than training over.
Withdrawal after a change
A house move, a new work pattern, a room rearrangement or the loss of a companion bird or person can all trigger a genuine decline in a bonded bird.