Diseased Bird: Puffy Junco

When I go near the feeder usually all the ground-feeding birds fly off. This bird stayed on the ground and just hopped away. It kept hopping away so I couldn’t get close enough to check if it was injured. I tried to put extra food on the ground, and then it flew to the top of the shed (other birds usually go to the adjacent tree). I put some food on the roof of the shed, but haven’t seen the bird since.