I read that the top ranking pullet will do this with the rooster too until they hit "puberty." At this stage I wonder if they may also be working out the pecking order more aggressively too. I have 12 chicks that are almost 4 weeks old too and I'm pretty certain about my two roos. One I'm 100% certain of based on appearance and behavior. I've watched several of the pullets do "the dance" with him from time to time but especially the dominate SLW pullet. The Sussex I highly suspect to be the roo is more passive/docile than the SLW roo but I've caught him alerting the others to danger a time or two and them all hushing and hunkering down. It's pretty fun to watch. He also appears a slightly lighter shade of brown, is larger than the others, and is feathering out much slower.