Hello, I seem to be having a serious issue with my "black" chickens attacking the other "golden" chickens. We believe that black ones are either black sex links or New Hampshire xBarred rocks (based on the pictures in a book). They seem to be attacking from the rear leaving large open wounds to the point where the chicken needs to be killed. We have also noticed that a few have been attacked on the tops of their heads. Is this the kind of breed or could it be something else? Any suggestions would be greatly appreciated! Thanks!