I have a flock of 11 birds, 4 RI Reds, 4 Ameraucanas and 3 Barred Rocks. Everyone has been doing fine until recently when I noticed feathers missing from almost all of their backsides. At first I thought they had mites but soon became aware that all were missing a lot of feathers except one of the RI Reds and she has a perfect plume of feathers. As I watched their behavior I noticed that she is pecking everyone on the back and some have patches the size of an orange. No blood yet but I'm concerned if it keeps up that someone will start bleeding. I think I'm going to have to separate her from everyone else for a few days or say goodbye. Any thoughts out there regarding this behavior?