If you've seen a Pileated Woodpecker, you remember. I first saw North America's largest woodpecker about a year ago, deep in the woods.
The big bird left me breathless as it swung away from a towering maple into the mist of a mid-march drizzle. The size of a crow with a two to three foot wingspan, this remarkable bird likely shredded a nearby tree for carpenter ants. If you live in a house with cedar siding, you might believe the Pileated to be a carpenter—a bad but persistent one at that.
How does this bird survive the repeated impacts to the head? With head trauma in football at the forefront of a national discussion, I've pondered how woodpeckers survive impacts to the brain, how bighorn sheep withstand violent collisions. After all, the force of each woodpecker strike is equal to a human sprinting headfirst into a wall at 16mph, probably top speed for most people. That passive curiosity went unfulfilled until I started researching the numerous physiological quirks of woodpeckers. Here are five key adaptations of the Pileated Woodpecker.
- Elongated tongue—the bird's tongue wraps around the back of its head and fuses to its nasal passage. Tongue is really a misnomer, as its actually called the hyoid bone. Wrapping around the brain, this tongue diffuses energy around the skull. You can see the shock absorption of the hyoid bone here.
- Makeup of lower beak—the upper beak overlaps the lower beak which is an advantage during foraging. The beak has a strong and dense layer of bone within the flexible outer layer. The flexible outer layer handles the initial shock and vibration. The strong and dense bone in the lower beak occurs a few millimeters in front of where it occurs in the upper beak. This positioning of strong bone in the beak allows the shock to be absorbed along the neck and throughout the body.
- Tightly packed cranium—the Pileated Woodpecker has reduced space between brain and skull. Upon impact, the bird's brain and skull decelerate at the same rate, rather than the brain crashing into the skull like a human brain would. The tight arrangement allows for the forces to be more efficiently diffused throughout the body.
- Spongy skull—the skull at the front of the head is spongy and absorbs forces well. Its flexibility acts like the crumple zone in a car where the front of the car crumples and absorbs energy while the car decelerates.
- Perfect Form—woodpeckers strike with perfect form. This limits the rotational forces acting upon the bird. A UCLA study found that when primates were struck with a linear force, they did not suffer concussions. Conversely, adding rotational forces will greatly increase the risk of concussions in primates. An example of a rotational force is whiplash in a car crash. Here is a great article talking about rotational forces and concussions and how bicycle helmets are (not) being developed to prevent concussions. Much of the information gleaned from rotational vs. linear forces was obtained from woodpecker research.
The Pileated Woodpecker has other adaptations as well, such as eyes with limited movement. If the woodpecker opened its eyes completely while striking 15-20 times per second, its eyeballs might pop out of its head! With these precise and efficient tools, the large bird can make quite the mess. Therefore, it has developed fine feathers within the nostril that prevent dust and wood chips from entering the nasal cavity.
We know a little bit about the Pileated Woodpecker. It's a big bird that's not difficult to study. Its habit of hammering its head against old and decaying trees makes one wonder how the bird withstands such a lifestyle. That's an easy question with some difficult answers. The harder questions might be more like, “How does a woodpecker locate its food?” “How did evolution balance the development of these features and brain trauma?” “Do the birds innately have perfect form, if so, how?” There are more questions that haven't been asked than answers.
Within the adaptations of this bird lie bigger questions about nature. One might ask, what good is the bird anyway?
The pileated woodpecker has informed research about concussions and the forces that cause concussions. The pileated woodpecker was a natural model for looking at eye movement in shaken baby syndrome and pinpointing how infant's eyes were being damaged. Today, there are thousands of people marveling at the big and curious bird as it drills through a decaying beech tree in the White Mountains of New Hampshire, an ancient cypress in Florida, or a western hemlock in Washington state's Puget trough. Near that region of hemlock, researchers concluded that the Pileated Woodpecker is a keystone species, meaning it is an uncommon species functionally linked to the survival of a suite of other species. Pileated Woodpeckers play a keystone role in organizing the old to mid-successional forests where they inhabit. At least twenty species can occupy a Pileated Woodpecker's cavity, including: wood duck, kestrel, saw-whet owl, big brown bat, fisher, and marten. The birds accelerate woody decomposition and nutrient cycling; they control insect outbreaks and modify the behavior of insects; they change the thermal properties of wood and open up overwintering insects to desiccation.
These are remarkable animals. Remarkable in their own right, but also remarkable for what humans can learn from them. Biomimicry—the imitation of models, systems, or elements of nature to solve complex human problems—is a fascinating field and provides a strong argument for the conservation of the world's biodiversity. A cure for cancer in the tropics is often tossed around, but there are animals, plants, and ecosystems here on the southeast glacial plains, organisms of which we know very little and of which we could learn very much. Aldo Leopold said “who but a fool would discard seemingly useless parts? To keep every cog and wheel is the first precaution of intelligent tinkering.”
Who but a fool could look at the earth and perpetuate only what is useful to him or her. Our entire world comes from the earth, that raw material of civilization. The earth, provider of things. But is that all? Look at the pileated woodpecker, look at anything in nature, really, and you'll also see ideas, the fabric of humanity. Recognize nature as an idea and you might reap its ideas—a sustainable vessel of creativity.
You might be able to find a pileated woodpecker in Faville Woods this winter. If not the bird, then certainly its large excavations on dying trees.
Written by Drew Harry, Faville Grove Land Steward
Photo by Photo by Nicole Beaulac, Flickr Creative Commons