American dipper in ice cave watermark

The dipper gets the distinction of being the only aquatic passerine (songbird) in North America. Remarkably, it makes its living diving and swimming in frigid glacier fed waters and then flies around in temperatures as low as -40 degrees. Adaptations that allow this bird to survive include an extra layer of feathering, an enlarged preen (oil secreting) gland for waterproofing, a nictitating membrane (third eyelid), enlarged muscles of the eye to accommodate for underwater vision, nasal flaps and increased hemoglobin levels to boost their blood oxygen carrying capacity that is essential for underwater swimming for up to 30 seconds at a time! I spotted this one along a partially frozen river as it entered a small ice cave in search of food.