Two of my four hens looked just like the pictures, bald a round the tail and vent, and it lasted for a year. The damage was done at night. The dominant hen (Buff orp.) only occasionally picked at them during the day. Nothing I tried worked. Until a few weeks ago, that is. Then, I did 3 things. First, I discovered to my horror that at least one of them had a severe round worm infestation. I treated them all for that. Second, a few days later, I when I changed the pine litter, which I do every 7 to 10 days, I took a chance and sprayed all the surfaces, and into all cracks or crevices, with Ortho Home Defense. I let that dry thoroughly, and put the pine litter down. (I scoop the roost every morning like a cat litterbox). Third, I hand fed the smallest hen, who was always squeezed away from the food, for a while (and her only), and set up a second feed station so she always had a one to go to by herself. This reduced the dominant hen's roughness for a while. Immediately, both Rocks began to grow feathers in the bald areas and they look normal and pretty again. Now, the trouble is, which remedy of the 3 did the trick??! Or were all three necessary?