I have a couple of chickens that seem to be picked on by the others. They have all been raised from chicks at the same time (they are now 11 months old). The chickens have all the feathers from the back of their neck picked off. I tried separating them, then putting them back together, but this doesn't seem to do the job. Do I have a rooster in the hen house? I'm not up-to-date on chicken behavior, so I hope I'm not asking a stupid question. This is only happening to 2 or 3 chickens out of a flock of 23. Any ideas? Thanks!