Woodpeckers go to astonishing lengths to feed themselves, repeatedly hammering tree-trunks at a speed of six meters per second. So why don't they sustain any head injuries? After two years of research involving high speed cameras and CT scanning, scientists at Beihang University believe they have the answer. Professor Fan Yubo says there is a combination of factors at work. For a start, he says the structure of the bird's beak directs force away from its brain.