To find out the science behind this superpower,
Lloyd wants to put Tilly to the test.
He's fitting her with a highly accurate GPS tracker
to measure how fast she can gain altitude
and a 360-degree camera to see exactly
how her wings are adapted to soaring.
[Lloyd] We’ll know exactly what you get up to.
Eh? You’re a good girl. Yes.
(Lloyd makes a chirping sound)
Go on. Off you go!
Go on!
[Narrator] Tilly soon finds an updraft
and soars high above the glen.
[Lloyd] Whoa-ho-ho! You make it look so easy, eh?
[Narrator] The onboard camera provides a wonderful opportunity
to see the world from an eagle’s perspective.
Throughout the flight, the GPS tracker and accelerometer on her back
are collecting important information.
Good girl. Clever eagle.
[Narrator] And Professor Jim Usherwood,
a locomotion specialist, can help interpret the findings.
[Jim] Well, it's really exciting, especially having the video next to it.
You can really see what's happening all the way through.
There you can see her climbing, circling seven times,
and then reaching quite a height, really very quickly.
She's doing, oh, three, four, five metres a second up – and that's fast.
That's sort of eight, nine, ten miles an hour – up.
Imagine running up a ladder that fast.
So she's climbing quickly?
Really fast, while hardly travelling across the ground at all.
[Narrator] Tilly climbs without flapping her wings,
saving huge amounts of energy.
Eagles are able to ride the air currents effectively,
thanks to their large wing area.
But the shape of their wing is different to that of many soaring specialists.
Albatross have very long, narrow wings,
which generate a lot of lift
for relatively small amounts of drag.
It makes them brilliant at gliding,
but this wing shape is no good to eagles.
Long wings are very good for gliding and soaring,
but they're horrible for flapping.
And of course, this thing at some point will need to flap.
- Yeah. - She’ll need a flap to take off,
carrying the weaponry to kill something and then carry that food back home,
at which point you don't actually want super-long wings.
[Narrator] Eagles have to deal with some conflicting tasks.
To soar well, it's best to be lightweight
with extremely long wings.
But to hunt large prey,
it's important to be powerful and heavy
with shorter, broad wings that can flap
and take off with big loads.
Eagles manage to achieve both.
But how?
The secret is at the end of their wings.
From the onboard camera,
it's clear that the feathers on her wing tips are separated when she flies.
Each one of these primary feathers
acts like a tiny aerofoil,
helping air hug the upper surface of the wing.
It means eagles can tilt their wings at very steep angles on takeoff,
generating lots of lift to support a heavy load.
It's also thought these slotted wing tips
can reduce elements of drag,
helping them soar with greater efficiency.
It's a clever solution for a wing that has to perform so many tasks,
helping them harness air currents
and dominate the skies.