I have two sets if guineas. The first set is older and was about a week old when I got them. They live with the chickens but definitely pick on the younger chicken. My second set of guineas was a few days old and raised from the get go with another batch of chickens and they're perfect little "chickens" or at least they think they're chickens, lol. None if mine are full grown yet so I'm just watching to see if we need to separate. The older group is about to go out into the pasture if they continue to pick.