Bald rump- Feather pecking? Roo?

[Xenia's Chickens]

One of my hens has developed a "bald" rump. The entire rump is involved, as well as some small areas on the "shoulders". It looks exactly like the pictures on the page [https://www.backyardchickens.com/forum/viewtopic.php?id=208399]. Within the patch, there are broken pin feathers, normal pin feathers and normal, but inadequately preened, mature feathers (sticking up in every which direction, barbs not smoothed out, etc.). Another hen has a bald head, with irritated-looking skin, but no broken or pin feathers. A few of the others have disheveled, but not bald, rumps.

The skin in the bald area is mostly normal, but one quarter-sized area looks irritated and scabby (not a wound, and not bleeding). I haven't seen parasites on any of them, although I've checked thoroughly, including at night. I haven't seen feathers in the pen, so it isn't a molt. I haven't seen any pecking, either. Egg production is fine.

I have a very (sexually) active roo. He's always been rough with the hens and has recently become aggressive towards me. All of them have been stuck in an 8x12 converted horse stall for 2 months because of several feet of snow on the ground, and a host of hungry predators hanging around the barn.

I'm inclined to blame the roo. Any thoughts?

 

[Baymen Moe]

Without any signs of parasites I'd say feather picking. I've had the same thing happen even though I have the so called prescribed space for my birds. It has been a tough winter for a lot of the country and being cooped up can cause boredom and picking.

You didn't say how many birds you have, it would be nice to rule out crowding.

 

[Xenia's Chickens]

I have 12. I have no doubt that they're bored. What can I give them to keep them busy?

 

[Baymen Moe]

I put a Flock Block in the run for them to peck at. It does help but not entirely. A little free range time as well, although that could be tough if you're still buried in snow.