by Alex Forsythe
The Hairy Woodpecker is often confused with the Downy Woodpecker. They are very similar in appearance, especially if they are not viewed together, but there are some differences. The first difference is the length of the beak. The Downy has a shorter beak, while the Hairy has a beak that is about the same length as its head. A HairyWoodpecker is larger than a Downy, has a longer black mark on the shoulder, a straighter posture when hanging onto a tree trunk, and never forages on weed stalks.
These little birds are tough! Humans are delicate creatures, requiring helmets, head rests and other devices to protect our brains from trauma. So how do woodpeckers, that bang their heads against trees up to 20 times per second, at up to 15 miles per hour, and up to 12,000 times per day, able to withstand such punishment? These impacts would easily kill a human. Fighter pilots can withstand 10 G’s, and humans often get concussions at 80 G’s. Woodpeckers withstand up to 1,200 G’s when pecking on a tree. To put that in perspective, 1,200 G’s is like slamming into a brick wall while traveling 26,000 miles per hour!
How does the woodpecker survive these extreme forces? The answer lies in the unique anatomy of a woodpecker. A woodpecker’s brain sits sideways in its head; it is 90 degrees off from that of a human brain. Why does this matter? The force of the impact is distributed over a larger area. Rather than impact the brain at the front point, the force is distributed so that less force is applied to any one area of the woodpecker’s brain.
The woodpecker’s brain is also more snugly fitted inside its head. Our brains suffer concussions with strong, sudden impacts because the brain collides with the skull. A woodpecker’s brain fits tightly inside the skull and cannot move or collide with its skull as easily. The large hyoid bones that wrap all the way around the skull act like seat belts for the brain, and the thick, platelike, spongy bone surrounding the brain serves as an armor.
The woodpecker also has thick neck muscles that serve as a sort of shock absorber, and the third inner eyelid helps keep the eyeballs in place. The beak also serves as a shock absorber, absorbing the impact rather than allowing the full force to transfer to the brain.
Another difference is the mass of the woodpecker’s brain. The mass of a woodpecker’s brain is about the same as that of two paperclips (2 grams). The mass of a human brain is 1,400 grams. A simple review of Newton’s second law of motion (F=ma) can help us understand the importance of this difference in mass. Force equals mass times acceleration. Assuming the same amount of speed (or acceleration), the amount of force placed on an object is proportional to the amount of its mass. If you drop your cell phone, it might incur slight damage. If you drop your laptop from the same height, it will likely suffer more damage due to its increase in mass and resultant increase in force. Therefore, if we banged our head with the same speed and force as that used by a woodpecker, the mass of our brains would work against us and we would likely suffer a concussion or worse, while a woodpecker simply flies to the next tree to start drumming again.
Scientists are borrowing from the woodpeckers’ unique adaptations to design helmets, protective coverings and other materials that will help protect members of the armed forces and athletes. As is often the case, we learn so much from birds and nature!