We've been having a similar problem with our arred Rocks & Wyandottes.
We were a bit slow in cleaning up their butts after they got a bit pasted up, and it seems that they've been rubbing their bottoms to relieve it.
Now, a couple of our birds have bald butts, and the skin is quite red.
Started...
Just found this website this afternoon; great site, great advice and comradarie! We're in the far Chicago burbs, out by Plainfield/Joliet area. (And yes, it's getting down below zero tonight.) My wife just couldn't wait for spring and she ordered some hatching eggs from Gabbard's in AR...