These birds can handle it because their bodies are designed to absorb the impact. Dense muscles, sponge-like bones and a third eyelid keep their brains - and eyes - intact. Let's take a closer look...
Even before the beak hits the tree straight on ( a millisecond), the thick muscles in the back of the neck contract. Because of this reflect, some of the force radiates down these muscles therefore protecting the brain from a full blow. Let's not forget the sponge-like bones that act like a cushion.
Another reason a woodpecker's brain is so well protected is because of its rigidity. Since their brains don't bathe in any spinal fluid, it doesn't bounce around with each impact. In fact, their brains are attached firmly to their skulls.
Also in that millisecond before the bill strikes the wood, a thick membrane closes over the bird's eyes, shielding them from any pieces of wood bouncing off the tree. The thick inner eyelid serves to keep the eyeballs in place, holding them back against the strong impact. As for the outter lid, it is rich in blood vessels, keeping the retina from being jostled around.
Other interesting facts:
- the nostrils are slit-like and covered with feathers protecting them from splinters and sawdust
- the woodpeckers are able to "hold on tight" when they drill thanks to their four-clawed toes (2 pointing forward and 2 backward) and their stiff tails
posted by snackshackforbirds.com
paraphased http://www.msnbc.msn.com "Why Don't Woodpeckers Get Headaches?"
