I've read about 12 pages of info on people with bald butt chickens, so apparently this is common. Most of the posters mentioned chickens who were swollen or distended in some way below the vent. My Australorp just turned one and now has a bald bum. There are no issues with pecking order - I only have 3 hens in a small backyard flock. There have been no new stressors. She seems perfectly fine, healthy, eating, happy and plucky otherwise. There is a small sore I noticed (pic with yellow arrow), but not sure if that's related. She seems happy and healthy, but with a bald bum. I've had 2 hens die of EYP in past and this doesn't seem like it at all. No signs of mites. Other 2 hens seem fine and have all their feathers. I'm at a loss!!! Thoughts? THANKS CHICKEN LOVERS!!!! Any advice is appreciated!!!