So, possible diffiency,probably not, with the free range. Change it up, put the baddies in their own pen. Spray bottoms with the blue stuff. If they don't quit...gotta go. I'll bet behavior MOD works... Seems They have little memory.
what the heck, culling? Omgosh. Let them out. give em a tiny pen, something out in the grass... hawks can't fly into a small narrow space, maybe chicken tunnels....no more feather picking will you find. Unless it's become ingrained behavior. But should still subside with the new area to...