Dippers

Dippers are small, chunky, stout, short-tailed, short-winged, strong-legged birds. They are unique among passerines for their ability to dive and swim underwater. Dippers have a characteristic bobbing motion when perched beside the water, giving them their name. While under water, they are covered by a thin, silvery film of air, due to small bubbles being trapped on the surface of the plumage. Dippers occur in the Americas, Europe and Asia. Unlike many water birds, dippers are generally similar in form to many terrestrial birds, but they do have some morphological and physiological adaptations to their aquatic habits. They have evolved solid bones to reduce their buoyancy, and their wings are relatively short but strongly muscled, enabling them to be used as flippers underwater. The plumage is dense with a large preen gland for waterproofing their feathers. Relatively long legs and sharp claws enable them to hold on to rocks in swift water. Their eyes have well-developed focus muscles that enhance underwater vision and they have nasal flaps to prevent water entering their nostrils.