I have 3 week old Black copper Marans and Amaraucanas in a brooder together. they have plenty of room for chicks their size, about 2 square feet per bird. Last night I was watching them. I can already tell the hens from the cocks (which I'm amazed at, again they are 3 weeks old) and obviously so can they. One of the BCM cocks decided to square off against the Amaraucana cock. I was amazed at how these two went at it. In the end the Amaraucana cock grabbed the BCM cock by the back of the head and slammed his face into the floor. The BCM chick retreated with haste. The Amaraucana chick strutted around spitting fuzz out of his mouth. You could almost hear him.. "EAT IT FRENCHY.... NEXT!!!" The hens are really busy establishing a pecking order as well. They just aren't quite so violent about it.