We've had three hens since March. All was harmonious until a few weeks ago when one started plucking feathers off another one's back. The victim was moulting so I thought that was the problem, separated them for a couple of days (they could still see each other) then put them back and all was fine until a week later when the aggressor basically ate quite a lot of the victim's rump, reducing it to a bloody mess of raw meat. The victim has recovered and we've partitioned the run using a large fly-screen so the aggressor can see the other hens but not bite them. But she seems depressed, with her tail down and less activity than usual though her comb is a good colour and her eyes are bright. It's too risky to put her back with the others so I don't know what to do. Given that she's vicious I can't really offer her to anyone else. I'm afraid that although she can see the other two she is languishing.