Rüppell's Griffon Vulture
One thing the filmmakers learned, according to Downer, was how birds use their feathers in flight. The key to the discovery was through the development of ultra-lightweight, onboard cameras.
"The size of the camera," he writes, "depended on the size of the bird. Large birds, such as Rüppell's griffon vultures [above], were able to carry a specially adapted HD camera about the size of a matchbox, that weighed little more than 3 ounces." The camera was attached to a foam mount, which was strapped to the bird's back like a tiny rucksack. "Within minutes the bird preened the harness into its feathers, so it was almost invisible, and it quickly seemed unaware that it was carrying anything at all."
The team had to position the camera so that it wouldn't interfere with the bird's flying, and they discovered that eagles, cranes, and geese hold their heads out front as they fly, while condors and vultures tuck their heads underneath once they become airborne. "With a camera mounted on a Rüppell's griffon vulture," writes Downer, "we could see the intricate way in which the feathers on its wings and body worked at take off, during flight and on landing."
"When the bird came in to land," he continues, "the onboard camera revealed how it slows to a stop. The secondaries drop like airbrakes, much like an aircraft's flaps, but the big surprise was on the wing's leading edge. All along this edge are what look like simple contour feathers, but as the bird slows down these flicked up, much like the slats on the aircraft that increase lift at slow speeds. Scientists are now studying the pictures we obtained as part of their study of aerofoil performance to improve aircraft wings."
In this photo, a Rüppell's griffon vulture flying over the great plains of Kenya is quick to spot a lion kill or the commotion of a crocodile attack in the rivers below.