A bullying bird may need a spell of quarantine
QI have one hen who constantly picks on another. Is this the pecking order establishing itself or is it bullying?
AAndy Cawthray says: If there is constant aggression by one bird toward another subordinate bird then this is unlikely to be the pecking order establishing itself, and it can be down to straightforward bullying behaviour. In these instances the bully should be removed from the flock and placed in a quarantine cage for a week or two until the subordinate gets a chance to settle.
Do not remove the bullied hen (unless it is permanently to a new location) as its reintroduction to the flock will invariably result in a return of the bullying behaviour.
Sometimes one chicken will show aggression towards another. If that happens, the bully may need quarantining for a week or two