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.
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.
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.
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.
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.
- 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.
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.