I've seperated the roos from the hens thinking this would solve the problem. Alas the problem still exists. We've had an invasion of field mice in the coop at night. Have put out poison (hens can't get to the poison) for the mice. Had heard that the mice may be the culprit of my hens loosing their feathers. 4 out of the 8 hens have naked patches on their backs, the neck and chest feathers looked very ruffled. They are still laying eggs. Anyone have ideas on how to help my girls get their back feathers replaced? I feel so badly for them. I've read somewhere that I can put tree sealer on their backs AND if it is one of the other hens pecking each other then I will be able to tell which hen because she will have the black tar on her beak. I'm thinking I will try this step next, since the other things haven't worked on clearing up the problem. ARGH !!