I tried putting chickens in with the older one today and she nearly killed one of the chicks. When I first put the 6 younger ones in the run with the hen who is about 4 months old and a rooster that is much older but I have no idea how old. They looked at each other and the bigger ones pecked at the ground by the little ones but did not attack them. Then the older ones went to one side to eat from their feeder and the little ones stayed in that area and went into the small ditches that are left after we buried the lower 6 inches of fence. When I checked a little later everyone still seemed ok. I check again before I had to leave and again they were totally separated. When my husband got home an hour later (they'd been out for 4 hours or so by then) The smallest chicken had all the feathers and skin pecked off her neck and her rear end. We removed here immediately, and the other 5 sometime later. When we went out to get the other 5, the hen was chasing one of the chicks but the rooster still wasn't paying any attention to them. So we suspect it is the hen. But what do we do now? The hen is the only one that survived from the batch of 6 chicks we bought in the spring. Our puppy got 4 when they got out of their pen and a new cat got the 5th. By then the new coop and run was completed so the sole survivor moved alone. She was alone about 2 weeks before we bought some more chicks and a rooster. When we introduced the rooster. The had a quick run at each other and were roosting together by morning. The rooster had been around all kinds of fowl before we bought him.