one abusive chook...:(

How long have they been together?

Take her away for a week, then re-introduce her to the others, this will soon sort her out.

Michelle

take her where?  don't have the room to segregate her..and what would a beak ring look like?

pop an extra feeder in, she cant be in two places at once! if you dont have anywhere to segregate, try dividing  the run with a little chicken wire and place the bully in there. Sometimes boredom can cause these vices to develop if previously they have been getting along OK. Do you a dustbath, or a pecking block of some kind, sweetcorn or a cabbage strung up might help distract her.