Migrating Geese Save Energy by Riding a Himalayan Roller Coaster

Migrating bar-headed geese are known for their incredible, no doubt tiring journeys, and new research shows that these birds save energy by riding on a Himalayan roller coaster.

Bar-headed geese (Anser indicus) can fly up to about 20,000 feet (6,000 meters) or more, soaring high above the Himalayan mountaintops. Scientists have long assumed that during their yearly travels before winter from their breeding grounds in Mongolia to southeastern Tibet or India, these geese would hit cruise control and remain at one altitude before making their descent down to Earth.

But now, according to a report in the journal Science, it appears that their migration is a rather bumpy one, with these animals riding the peaks and valleys of the Himalayan Mountains like the hills and dips of a roller coaster.

This flight strategy may seem tiresome, but it actually allows the ingenious birds to conserve energy while flying, researchers say.

Bar-headed geese are heavier than most other bird species, yet their average heart rate for the journey from Mongolia to India was only 328 beats per minute, compared to values of around 450 bpm recorded in wind tunnels or on rare occasions in the wild," co-author Nyambayar Batbayar said in a press release.

"Bar-headed geese have found a way to cross the world's highest land massif while remaining well within their physiological capabilities," he added.

Batbayar and an international team from Canada, Australia, Germany and the United States used custom-designed sensors implanted in the birds' abdomens (which did not harm the birds) to measure their heart rate, altitude and other factors during their southern migration. The data showed that in order to cope with the low density air at higher altitudes over the Himalayas, they dip and dive with the terrain to conserve energy.

Not to mention when they fly at lower altitudes they can breathe in more oxygen, also relieving some of the birds' burden.

Of course, other bird species use different strategies that work for them. Some fly at high altitudes to take advantage of the tail wind while others glide during flight.

Regardless, co-author Graham Scott added, "they are able to accomplish something that is impossible for most other birds."

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