My chickens have started picking at each other's feathers! Why are they doing this? They chase each other around and yank out a feather. Now I have one chicken with a bald butt, one with a bald patch on her back, and my silkie has a bald patch on her head! Why are they doing this and how do I get them to stop? They are in good health otherwise, too young at 7 months to moult, have good nutrition except they can't free range for bugs in this weather, and they can't be overcrowded with 10 chickens in a 8 by 12 coop with a large yard. Are they just bored?