What Bird Rides the Wind Like a Roller Coaster?
As we move into winter, our feathered friends in the Northern Hemisphere are doing some hard labour – as migratory birds make their way back north. One species outshines all the rest: the bar-headed goose, superhero of the skies. Twice a year, these birds skim the world’s tallest mountains in the Himalayas. Reaching altitudes of up to 10,000 metres, the birds soar to the edge of the stratosphere, where otherwise only passenger planes dare fly – setting a world record in the process. Up there, strong winds, temperatures of -30°C and oxygen-thin air are the norm, so how do the birds cope?
Scientists from the UK’s Bangor University have found the answer: their flight patterns mimic those of a rollercoaster. Flying 6,000 metres above sea level is debilitating even for resilient bar-headed geese, causing their heart rates to rocket and their wing-beat frequency to increase. So these birds maintain an ideal height of just 60 metres above the Earth’s surface, adjusting their route to the terrain. The geese don’t care whether they’re flying in a valley or over the highest mountain in the world. Staying close to the ground means they only have to spend 2% of their time in the air above 6,000 metres. Combined with their tactic of capitalising on strong updrafts and flying during calmer evening hours, this allows the bar-headed geese to conquer even the tallest mountains.
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