This past spring I acquired 6 production reds and 2 leghorns. All are laying. In july I got six more chicks, 2 easter eggers, 2 barred rocks, 1 blue andalusian, and a mystery chick (slate grey legs so I assume an americauna). When I received the chicks the mystery chick was a lot smaller than the others and, although fully feathered, it is still about a third smaller than the rest. About a month ago I integrated the chicks and everything went rather peacefully. However, lately one of the reds has taken to picking on the mystery chick. During the day all is fine, the run is large enough that the chick can stay out of her way, but at night it gets so bad the red runs the mystery chick out of the coop. When I go out to lock the coop the chick is huddled somewhere in the run. As soon as I put the chick in the coop the red will jump down and try to chase her out. I now do it after dark so the red can't see her when I close the door. Is the only solution to remove the red for a few days and let everyone else re-aclimate then reintroduce her to the flock? Any help would be greatly appreciated.