I used to own chooks. I had about 30 in a big chook house with a long run. There was always one chook who got picked on by the boss chooks. If I moved the victim chookie to its own area to keep it safe, the boss chooks would very soon find another chook to pick on. It was like they thrived on picking on one chook, and didn't really care which one it was, as long as there was one. 

Sometimes I would feed them some treats so I'd return the victim chookie to the flock so they could all share, but it never worked out satisfactorily. As soon as the boss group noticed the victim, they'd tear across the pen and start pecking it. Even the treats couldn't distract them 😞 

in the end, I decided the only answer was to remove the boss chook group to their own area. They sulked and scrabbled about for a day or two, but pretty soon they found one of their own to peck...