I initially started out with 10 birds, one of which was a rooster. As he matured with the rest of flock, he dominated all the hens, and was very rough on them to the point that he abused one of them almost to death. So, I removed him from the coop/run. You could almost see the stress just melt...
I am a first-time chicken guy, and I have 8 hens in a secured coop. I don’t allow my hens to free-range because of the predators in the area. One of my girls, my only totally black hen, has had an open sore spot on the back of her head for some time, which I thought was due to the other birds...