I have read several threads on this subject but still did not find the answers I was looking for, at least not a similar situation such as mine. I have a mixed flock of Barred Rock, Black Star, 2 Buff Orpingtons, Silkie, Silkie bantam and 4 guineas (guinea sexes unknown as yet) that are all approximately 12 weeks old. Now, my daughter wants to add an 8 week old Silkie to the mix since we lost our older Silkie (in an older flock) a couple of weeks ago. They are in their own temporary coop for the moment, next to the older pullets where everyone can see each other. The older pullets have been laying about a month now (hatch date April 7, 2014) and the younger flock will be integrated in a couple of weeks to the older pullets. Currently, they all free range at the same time and occasionally, one or more of the older pullets 'goes after' one of the younger ones and I intervene and shoo them back to their area. Should I add a new Silkie or not? And if ok, can I immediately add the new Silkie to the younger flock and pretty much be safe in free ranging her with her flock mates? So far, the only aggression I have seen is 2 of the guineas towards the BR and the BR towards the Black Star on occasion.