I have 16 pullets and 3 cockerels all 14 week old Black Australorps. One of the roosters continually grabs the hens by the back of the neck. I can't tell if it is the same hen or different ones because they all look the same to me. The other 2 roosters don't seem to exhibit this behavior they don't appear to even crow yet. I don't need roosters I just got them to hear them crow. Should I cull this aggressive rooster or is this natural behavior?