I don't know about the hens, but my roo Mr. Vic pretty much raised my flock after I got them out of the brooder at about 3 weeks. He was an adult when I got him, and did so because I have yard cats. The intention was he would keep the cats from being too interested in the ladies. Well, he didn't seem to pleased at first, but he was never mean. They wanted to cuddle on the roost, but he only let a couple get too close. Of course, the girls are all grown up, and he seems quite pleased with his harem, all 'cept that darn roo in the mix. He even taught him the ropes, but now that Roo is 7mons and wanting a piece of the action, he gets chased around the run. Much I think is playfullness, but still he does his job without getting really violent.
That said, the most violence I have seen from my flock is from the ladies. Beware, they take that pecking order shiite serious... I've seen quite a few full on floggings like a couple of gamecocks getting it on. Not to mention the nightly fights over who is roosting where. Throwing small chicks into that mix doesn't seem like a good idea to me. My girls, as boisterous as they are, have never really hurt each other. Vic does a good job of putting offenders in their place. But small chicks? Only with a broody mom or at least an adopted one...
