Chickens pulling tail feathers.

[Rooster49]

I have 6 chickens all the same age about 4 months old. There are two that are pulling out the tail feathers of the other chickens. Four have almost no tail feathers at all. I don't know if it about establishing the pecking order. But one I had to separate because she was starting to bleed from her tail.
How can I stop them from doing this.

 

[sourland]

Do they have enough space? This is frequently a result of boredom or overcrowding.

 

[Rooster49]

Yes the run is about 16 X 8 feet
in the coup Two perches (polls) 4 feet all sit on top side by side.
plenty of feed and water

 

[enola]

What are the deminsions of your coop??

 

[Rooster49]

4X8 feet

 

[aart]

What are you feeding?
How many pullets(girls) and how many cockerels(boys)?