Now, a team led by researchers from Bangor University has tracked the flight and revealed the basis for the birds' "rollercoaster flight" pattern.
The findings, published in Science, show how the birds hug the mountainous terrain, and that this saves energy.
Bar-headed geese have fascinated biologists for decades.
They achieve physiological feats that seem impossible - flying at extreme altitude, where there is less than 10% the oxygen found at sea level.