Hitting a tree, all day
Why Doesn't a Woodpecker Get a Headache?
It hammers wood twenty times a second. Being small is most of the reason it survives that.
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Step 1 of 5
A brain is hurt by being shaken, not by being hit.
In a knock to the head the skull stops and the brain inside keeps moving for an instant, then slaps into the bone. That is what does the damage.
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Step 2 of 5
A small brain is much harder to shake.
A woodpecker's brain weighs about two grams. Small light things take far less punishment from the same jolt than big heavy ones do.
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Step 3 of 5
It is packed in tight, with almost nothing to slosh in.
Yours floats in enough fluid to travel a few millimetres. That is the difference The brain is held snugly against the skull with very little fluid around it, and it is a tall narrow shape pressed flat to the bone. There is barely any room to move.
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Step 4 of 5
And every blow is aimed dead straight.
The head travels in a straight line and stops in a straight line. It is the twisting kind of blow that injures brains most, and a woodpecker almost never gets one.
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Step 5 of 5
The tongue does something odd on the way past.
It is so long that it wraps up over the back of the skull and round to the front. Useful for hooking grubs — and it happens to sit like a strap over the brain case.
Researchers filmed the strikes closely in 2022 and found the head barely cushions at all — it is simply built too small and stiff to be hurt.
The short version
A woodpecker is unharmed because its brain is tiny, packed tight with no room to slosh, and struck straight on rather than twisted.
Try it yourself
Shake a jar with a grape in it, then one packed to the brim. The packed one cannot rattle — that is the woodpecker's skull.