If head trauma is so bad for humans, how do woodpeckers manage?

They have a very strong skull.  Really!

https://www.livescience.com/19586-woodpecker-skull-concussions.html

I'm laughing so hard the tears are rolling down my face.  What a great question. :)

Unique skeletal-muscular composition, along with highly specialized cushioning structures in the head and neck, enable woodpeckers to bang their bills on firm structures without injuring themselves. In this way, they often communicate by “drumming” on trees, snags, and man-made structures, such as wood siding of homes.

Woodpeckers are not human. 

Pretty interesting:

https://askabiologist.asu.edu/plosable/woodpeckers