While excavating a cavity, a woodpecker’s head can strike a tree’s surface at speeds up to 13 - 15 mph and do it at over 100 strokes per minute. This is equivalent to a person crashing head-first into a tree while running at top speed.
In order for woodpeckers to survive the 10G's of force that they can sustain with every blow against a tree, they have the following special adaptations:
- The bones between the beak and the skull are joined by a flexible cartilage, which cushions the shock of each blow.
- The skull is made of spongy, air-filled bone and the brain is packed very tightly into the brain cavity, with little room to rattle around during impacts.
- The shear force from each blow is directed not to the brain, but downward towards very strong neck muscles that act as shock absorbers.
- A woodpecker’s head and body are always in a perfectly straight alignment when hitting a tree to avoid breaking its neck.