I've noticed my 3 slightly older pullets (I raised them together) will sneak up behind my two younger BR pullets and yank their tail feathers. They're not going as far as to deliberately pluck them out - they just seem to enjoy startling the youngsters & getting them to squawk. I've seen one of my RIRs hold on to a BR's tail feathers as she franticly tried to free herself. Other than trying to keep the BRs away from food; there are no other acts of aggression, I never see any blood or other signs of injury and the tail feathers are never pulled out. It just seems like the older hens are just being "mean girls".