The short answer

Woodpeckers avoid brain damage thanks to special adaptations in their anatomy. Their skull, jaws, eyes, and tongue are all uniquely designed to help absorb the impact of the constant pecking and prevent concussions and retinal damage.

The long answer

To us humans, banging your head against a wall sounds like a regrettable moment of frustration. To woodpeckers, it sounds like a Tuesday.

Woodpeckers rapidly peck trees so they can uncover food, create nesting spots, and communicate with other birds. The pileated woodpecker native to North America can peck up to 20 times per second, up to 12,000 a day, with a force of 1,200 g each time. That would be like a human smacking their face at a wall at 16mph (~25km/h). Ouch.

The head pounding bird has evolved with several mechanisms to prevent brain damage, concussions, retinal hemorrhages, and, frankly, their eyes popping out of their heads.

Reason #1: A woodpecker's skull, brain, and jaw have evolved to protect against damage.

To start, the woodpecker’s skull is made up of fairly spongy bone to help absorb the impact, and there is also very little fluid surrounding the brain, which makes sure there isn’t a lot of room for the brain to bounce around. Strong jaw muscles tighten up a millisecond before the strike to create a snug cushioned surface to spread the force of the impact. Additionally, their brain weight to surface area ratio is quite small, which makes the impact of the peck spread over a larger area, reducing the likelihood of a concussion compared to us larger-brained animals.

Reason #2: A woodpecker's eyes are designed to prevent the eyeballs from popping out.

Woodpeckers’ eyes also have a few tricks up their sleeves. Right before the impact, a third eyelid closes over and acts like a seatbelt to prevent the eyeball from popping out of the socket.

They also have extra cushioning reduce strain and part of the eyeball fills with blood to temporarily increase the pressure to keep the eye in place.

Reason #3: A woodpecker's unique tongue helps absorb the impact.

Lastly (and this one’s my favorite), woodpeckers’ tongues act as a sort of sling to absorb the impact of the peck. Their tongue uniquely starts at the top of the beak, wraps around the head, and comes back forward through the lower jaw.

The tongue starts at the top and wraps around the skull to finally exit the tongue.

Every time the woodpecker strikes its beak against a tree, the tongue acts as a shock absorber. Their tongues are incredibly long, stretching out as far as 4 inches (~10 cm)!

As a bonus for getting to the end of this article, here's a picture of a juvenile woodpecker sticking out its tongue. 😛

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Sources

Lederer, R. (n.d.). Why do Woodpeckers Peck?. Ornithology. https://ornithology.com/why-do-woodpeckers-peck/

Schwab, I. R. (2002). Cure for a headache. British Journal of Ophthalmology, 86(8), 843–843. https://doi.org/10.1136/bjo.86.8.843