How bar-headed geese fly over the Himalayas without sweatin’ it
Climbers who hack and wheeze and struggle their way up the icy, 4-mile-high peaks of Mount Everest are appropriately shocked when they see birds casually flying above their heads. These birds are known as bar-headed geese, and evolution has tricked them out to be able to fly at heights of 20,000 feet.
Bishop and his colleagues also were amazed to find that the geese cross the Himalayas in a single day. To fly so far at such a great height, the bar-headed geese must sustain a 10- to 20-fold increase in oxygen consumption. By comparison, lower-altitude birds such as the Canada goose cannot sustain resting levels of metabolism at 30,000 feet. Bigger wings, bigger lungs, a dense network of capillaries surrounding the flight muscle, and hemoglobin that more tightly binds oxygen to the lungs work together to sustain oxygen flow throughout the bird’s circulatory system, including its flight muscle. Improving the understanding of why tissues in bar-headed geese are so adept at taking up oxygen might elucidate human respiration as well.
