Slamming your head full force into a tree trunk could knock you silly. Yet woodpeckers do this untold thousands of times during their lives, and these birds have thrived for 25 million years.

But research published on Friday shows for the first time that all this pecking does seem to carry consequences for the woodpecker's brain. Scientists said an examination of woodpeckers' brains found buildups of a protein called tau, which in people is associated with brain damage from neurodegenerative diseases and head trauma.

The researchers examined brain tissues from downy woodpeckers and red-winged blackbirds, a nonpecking bird, from collections at the Field Museum in Chicago and the Harvard Museum of Natural History. The woodpeckers had tau buildup. The blackbirds did not.