Why don’t woodpeckers get concussions?

A female Pileated Woodpecker has been excavating many large holes on a neighbor’s tree.  At first I thought (and hoped) she was excavating a cavity for a nest, but no such luck.

female Pileated Woodpecker-1

The female Pileated has a black whisker stripe behind the bill, while the male’s is red.  She has been a regular visitor to this tree for most of a week, and has enlarged the excavation noticeably each visit.

From the extent of damage along the length of one of the trunks of the tree, it seems more likely that she is just digging for insects, and these particular insects live pretty deep in the tree and are spread out in many pockets of the wood.

female Pileated Woodpecker-

She has worked her way down the trunk about 6 feet. Other woodpecker species have also checked out her work and drilled a few of their own holes in this long stripe.

If you haven’t watched a Pileated Woodpecker go about their excavation, it bears some description.  They open up a wide cavity by judicious pecks with their chisel-shaped bill at just the right angle to flake off large chunks of wood.  Hit it from the right and down, then from the left and down, repeat once or twice, and a big wood chip goes flying.  The pile accumulating at the bottom of the tree grows each day the woodpecker visits (always the female), and she works at it for 1-2 hours at a time.

female Pileated Woodpecker-

She closes the nictitating membranes (white covering) over her eyes just as her head makes contact with the wood.

Every now and then she stops, looks into the hole, flicks out her tongue and snags some hapless crawling thing, and then continues the destruction.

female Pileated Woodpecker-

Her tongue protrudes from the tip of her beak as she probes into the most recent patches of her digging.

female Pileated Woodpecker-

She seems to have uncovered a whitish cylindrical mass, perhaps a larva buried deep in this wood.

She hammers away for extended periods of time with an acceleration force of 1000 x g  — an impressive feat when you consider that humans can withstand no more than about a 100 x g acceleration.  So, how do woodpeckers avoid getting concussions from all that hammering?  It turns out they have multiple safeguards against injury from chiseling wood.

  • First, it should be noted that woodpeckers typically excavate rotting wood, which tends to be softer after decomposing fungi have been at work. The beak penetrates the wood, rather than stopping at the surface with collision impact.
  • Second, woodpeckers strike the wood at an angle, giving it a glancing blow, and the beak makes contact for just micro-seconds, which lessens the impact. Because bottom bony part of the beak extend further than the upper part, the brunt of the blow is transferred to the lower part of the bill which is not connected to the braincase.
  • Third, woodpeckers have unusual skull anatomy that acts like a shock absorber, with elongated (hyoid) bones and muscles that support the tongue wrapped around the back and top of the skull.  Cranial bone of woodpeckers is spongey and composed of plates that slide over one another to absorb the force of a beak strike.
Flicker-Tongue-from birdwatchingdaily.com/blog

A diagram of the Flicker’s very long tongue shows how the tongue support (hyoid bones) curves from below the beak around the back and top of the skull.  Not only do the hyoid bones and muscles act like shock absorbers for the skull, but the spongey nature of cranial bone with diffuse air pockets embedded in the bony layers helps absorb the impact of the blows.  Birdwatchingdaily.com/blog — 12/10/13

  • Fourth, and importantly, reduced fluid cavities in the woodpecker brain mean it does not slosh around in the cranial cavity as the human brain does upon impact with an immovable object.  It is the impact of brain tissue with cranial bone that causes concussions in humans.  With the woodpecker brain tightly encased in spongey bone and restrained with hyoid muscles and bone as a seatbelt, the brain is well-protected from concussive forces.
woodpecker helmet

The woodpecker helmet — Toronto Star sports page, Oct. 27, 2011.

It’s amazing what we can learn from the “lessons of nature”.  With what we now know about woodpecker skull anatomy, perhaps sports helmets of the future may incorporate some of the features that protect bird brains from concussion.

8 thoughts on “Why don’t woodpeckers get concussions?

    • Thanks so much for your kind comment. I think that bird was so intent on finding goodies it didn’t mind me getting close. Of course 600 mm of telephoto helps too!

  1. How disappointing that she wasn’t excavating for a nest!! But I love the pic where you got her tongue capturing her prey. And fascinating stuff on the flicker’s tongue – I love it!

  2. Extraordinary Sue … both info and pix. Coincidentally, I just looked out to see a pileated on a backyard cottonwood. And per our prior notes, I’ve written BB into a future nature photo presentation. Thx.

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