I have a Svarthöna cock that is just about a year old. He has been keeping his tail lower than usual the last several days. I thought it was due to the weird weather. Other than the tail I haven't noticed anything off, but when I checked him over tonight, I found that he has a large, hard knot at the base of his tail, and what looks like large scabs. I haven't noticed him itching back there (I see him several times a day) and there are no signs of lice or mites. He is the only rooster in the coop and the hens don't seem to pick on him. The hard lump is a little bigger than a golf ball. I thought I caught a picture of the preening gland, but of course when I got inside, I was wrong. The gland itself looks yellow with a small black head on it. I am thinking it is either a tumor, or more likely a clogged oil gland. The first picture is of the side base of the tail. The second picture is above the vent. Sorry about the bad pictures, but it is getting dark. Maybe I can get better ones in a couple of days. (Tomorrow is likely too busy to get pictures while the sun is out.) Is there anything that I can do for him?