Diseased Bird: Mourning dove in some sort of gastro-intestinal distress

The underside of this dove’s tail is caked with excrement. Initially saw the bird on the ground under a pine tree where I scattered food. It was pumping it’s tail up and down similar to the way birds do when they poop. I then noticed that the underside of the tail was caked and the bird was apparently having no success in eliminating. A portion of the breast feathers were in an odd position but that may not be related. I walked outside to try to get a photo and the dove flew up and landed on the fence between me and my neighbor. The dove eventually flew off with it’s caked undertail.