Unusual Bird: Ruffled feathers on Carolina Chickadee

An interesting chickadee who is a regular visitor at our feeders & bird bath. A Carolina chickadee who seems to have some deformity, injury, or disease? It has no trouble flying or getting around. The rumpled feathers never retract/smooth, always in that ruffled position. It certainly does not look or act sick. We would like information about what this could be.