American dippers are rotund little birds, with stone-gray bodies that bob rhythmically up and down, as if mounted on springs. why do they “dip” like this? there are three theories. one possibility is that the dipper's repetitive bobbing, against a background of turbulent water, helps conceal the bird from predators. a second theory is that dipping helps the bird spot prey beneath the surface of the water. but this theory about why dippers dip holds the most promise: dipping may be a mode of visual communication between these birds in their noisy environment.