Adaptations.

To prevent damage to the brain caused by the rapid and repeated impacts, woodpeckers have evolved several adaptations to protect the brain: it is small-sized, orientations within the skull are such in order to maximize the area of contact with the skull and the brevity of contact. In the millisecond before each impact, a membrane covers the eye, protecting against shrapnel. The nostrils are small gaps and have special feathers to cap them. Thus, the woodpecker are capable of repeatedly pecking the wood of a tree, suffering deceleration in the order of 10,000 m/s. 

Thank you, Scientific Philosophy and Philosophical Science.