JOIN USResearchers at Vancouver's University of British Columbia (UBC) say these geese have a higher density of blood vessels and other unique physiological features in their flight muscles.
This allows them to do what even the most accomplished athletes struggle to achieve, exert energy at high altitudes, according to a university statement.
The geese, which are identifiable by the dark stripes on the backs of their heads, fly over the world's highest peaks to migrate annually between India and China and Mongolia.
"They fly at altitudes up to 9,000 metres. That is the equivalent of humans running a marathon at the altitudes commercial airlines fly," said zoology research student Graham Scott, who was part of the research team comprising scientists from the UBC and the University of Birmingham in Britain.
As part of their research, they compared the physiology of bar-headed geese to low-altitude waterfowl such as barnacle, pink-footed and greylag geese.
"We found approximately six to 10 percent more aerobic muscle fibres in bar-headed geese compared to low altitude birds. There were also more capillaries -- the body's smallest blood vessels -- surrounding these fibres in bar-headed geese," said Scott.
He said they also found that the geese's mitochondria -- the cell's power sources -- are distributed closer to the cell membrane and therefore closer to capillaries.
"These traits allow oxygen to be carried and diffused more effectively to the flight muscles," said Scott, who has previously found that bar-headed geese are fine-tuned for flying high as they breathe more when oxygen is scarce than most other animals do.
The study, which has been published in "Proceedings of the Royal Society B: Biological Sciences" this week, will allow scientists to better understand the limitations of human physiology and find ways to exceed them, the university statement said.