I have 19 hens and one that looks like it might be a rooster. They have a 10' x 12' chicken coop with roosts, nests and plenty of room. They also have an outdoor chicken run the same size. In addition, they get out in the evening for about an hour (they can't do too much damage in an hour). So, if they have plenty of everything why are they so aggressive with each other? I've seen them pull each others tail feathers out and chew on them or just bite (peck really hard) each other. They haven't brought blood yet, as far as I know but I don't know what to do about this behavior. Any suggestions?