大象传媒

When watching a cockatoo chase away a hawk, CrowdScience listener Alison saw the hawk find a thermal and get carried upwards. The cockatoo pursued it, but the hawk flew higher and higher until, as Alison says, 鈥渋t was just a tiny speck, hardly visible to the naked eye鈥�.

And that got her wondering... what height could that hawk have actually reached? What altitude restrictions do birds have? Could any species, whether it鈥檚 a cockatoo, a finch or a duck, go that high if they wanted to?

Alison, who lives in Sydney, Australia, decided to put those questions to us, and presenter Alex Lathbridge gets on the case. In a previous episode Alex explored a similar query 鈥� but with insects. He returns to that show to explore the biomechanics of high-altitude flight and what challenges any airborne species 鈥� whether it鈥檚 a bee or a buzzard 鈥� have to overcome.

At altitude the air density is lower, meaning that there鈥檚 less oxygen available and less lift from wings. Alex talks to biologists investigating the physiology of birds and discovers how some species have adapted to overcome this, including some of the very highest-flying birds like bar-headed geese, whose migration takes them over the roof of the world, the Himalayas.