I have 2 BR roos, 6 BR pullets, 23 RIR pullets, 2 Ameraucana pullets, and 2 Ideal pullets. They are all about 11 weeks old. The roos have never been too friendly, but they will eat from our hands. For some reason, the roos have begun to act aggressive toward the BR pullets when I hold them. They get all puffed up and try to peck their heads. They don't do this to the RIR's or others when I hold them, just the BR's. They don't act aggressive toward them at other times, just when I hold them and they start cooing. Any ideas why?