Learned my lesson the hard way: do not introduce younger chickens to older ones w/o being there to supervise. We've got 2 standard & 1 bantam adults, 2 "tweens" (3 months old), and 5 chicks (3 weeks old). I haven't been worried about the adult bantam cochin, who will chase/challenge the younger birds but can't do much damage due to a crossed beak but the standards (BSL, RIR) have proven themselves to be vicious. The tweens have been sleeping in the coop, separated from the adults by chicken wire, for over a month now. They're on the same roosting bar, even. When theyve been in with the adults, the adults have ripped out feathers & chased them but that's been it. For some dumb reason I decided to leave them all alone in the run on Saturday while I ran errands. I knew that DBF would be back in a couple of hours, so I figured hed check on them and separate them. He told me later that when he came home, he saw the tweens & adults were all in together (although in separate areas) and decided to leave them be. When I got home I called for the chickens. Only the adults came running. I could hear one of the tweens but couldnt see her. So I put the adults into their small run and went looking for the tweens. I finally looked up and saw them in the next door neighbors yard, stashed in their rabbit hutch. Yes, the same neighbors who have 2 loud, barking dogs. When I went to retrieve the tweens, I got the rest of the story. Apparently the adults had tormented the tweens so badly that the tweens squeezed through the fence to escape, where they were quickly found by the dogs and chased yet again. The neighbors caught the young chickens and put them into their rabbit hutch. When I got home, the tweens had been there for about an hour. The poor girls were clearly stressed: panting and pacing. Croquette, the BA, is fine. She was really talkative afterwards and when DBF picked her up she rested her head on his shoulder. Curry, the BO, got the worst of it. The adults tore her skin on the side of her head above her ear. It was pretty gory and was open about 3/4 the size of a dime. I could see that it could open more but I left it alone. It has since scabbed over and shes eating/drinking/walking just fine. It doesnt seem to bother her. The poor thing was so clingy and seemed to need comfort. She just wanted to sit on my lap and hid her head in the crook of my arm. She's terrified of the adults now and won't go near them. I put up rags on the chicken-wire barrier in the coop so that they don't have to see each other. Before I did that, the tweens cowered in the nesting boxes. That's a habit I don't want to have to break. Old strategy: 1. Integrate 2 tweens with 3 adults before putting chicks in the coop in another week. 2. Slowly integrate chicks into adult flock in the fall. New strategy: 1. Integrate chicks in with tweens to create a 7-chicken flock as soon as the chicks can sleep outside. 2. Integrate 3 adults into the bigger 7-bird block. The standards are the biggest problem & threat, so I need to give the younger birds lots of time to grow and gain strength. 3. Put chicken wire along the rest of the fence between our yard & next door. The tweens so far get along just fine with the 3-week-old babies, who spent much of the weekend outside with the tweens. The pipsqueak splash Polish (who is about 4" tall right now) challenged my foot-tall BA for a sliver of pork. She jumped up, talons out, and went for Croquette's chest. She didn't hit Croquette, but it was pretty darn hilarious to watch. The BA won but that puny little Polish is going to be a force to be be reckoned with!