UpbeatVultures ride 'free fuel' from the sky, a study of 4.3 million kilometres shows
Soaring birds barely flap. Tracking seven vulture species over more than 4.3 million kilometres (2.7 million miles) of flight, researchers publishing in Science found the birds flapped for as little as 0.1% of their travel time, riding rising air the team describes as free fuel from the sky — moving more cheaply, at their best, than swimming. Heavier soarers saved the most energy, though they must wait for the right weather, a trade-off that will shape how migrations shift as the climate changes.
The upbeat factorthe sky itself is a fuel station — and the biggest birds have known it all along.
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