Adaptations
Unlike many water birds, dippers are generally similar in form to many terrestrial birds (for example they do not have webbed feet), but they do have some morphological and physiological adaptations to their aquatic habits. Their wings are relatively short but strongly muscled, enabling them to be used as flippers underwater. They have dense plumage with a large preen gland for waterproofing their feathers. Relatively long legs and sharp claws enable them to hold onto rocks in swift water. Their eyes have well-developed focus muscles that can change the curvature of the lens to enhance underwater vision. They have nasal flaps to prevent water entering their nostrils. Their blood has a high haemoglobin concentration, allowing a greater capacity to store oxygen than terrestrial birds, and allowing them to remain underwater for up to at least 30 seconds.
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