He has had a bare bottom, like a big bare patch around his vent for probably over a year now. He has been one of two roos, and he has been the only roo and he has been through a molt and those feathers have never grown back.
I haven't checked too closely for lice or mites because he is the only bird I have ever had who has had this problem. I tried googling and searching but there isn't much on this topic. Any advice would be appreciated.