

Taking a winter walk in the forest across the road from our cabin, my son, Jim, and I were made acutely aware of two denizens of the deep woods and streams who illustrate the actions of entropy better than any other animals I know. It began where the forest gives way to wetland. This is beaver territory, and over the past year, the local beavers (see Fig. 1 for their home) apparently decided that there were too many trees in an area about 100 by 200 feet. They pretty much clear-cut the area of smaller trees and are busy with a larger project – trying to cut down a large ash tree (Fig. 2). Why is a good question because ash is definitely not one of their favorite forms of food. At least, chewing on the hard ash wood would keep their front teeth from growing so long that they would interfere with normal feeding.
Farther into the forest, we came upon several trees that looked like they had been attacked by a child with a small axe (Fig. 3). These are trees that have been attacked by pileated woodpeckers (Fig. 4). Pileated woodpeckers are presently the largest woodpeckers in North America. The presumably extinct, ivory-billed woodpeckers were larger, but even so, pileated woodpeckers are the third largest species of woodpecker in the world. Pileated woodpeckers like to inhabit large mature hardwood forests where they focus on dead or dying trees that are home to carpenter ants (another major member of the forest demolition team) and various tree beetles. These insects are the main food of the woodpeckers, and they spare no energy trying to extract these insects from the rotting wood.
Woodpeckers, in general, make two types of holes in wood. One is the result of going after insects. These holes are relatively small and irregular in outline (Fig. 5). Once the hole is made, the woodpecker inserts its long and highly specialized tongue into the hole and probes for its insect food. The tongue of a pileated woodpecker is very long and actually wraps around its brain. If our tongue had the same arrangement, it would be two feet long! On the inside of the tongue is a core of bone, which is surrounded by softer tissue. The tip of its tongue, which can protrude past the bill, is barbed, so if it spears an ant or a beetle larva, the insect is impaled on the tongue.
The second type of hole is much larger and more regular in outline (Fig. 6), and it is used for nesting purposes. As would seem appropriate, a pileated woodpecker lines its nest with wood chips and then lays about four eggs in the nest. After the young have hatched and fledged, the nests are often re-used by other birds, squirrels or even by racoons.
You may wonder how a woodpecker can repeatedly ram its beak into hard wood without scrambling its brain. Just imagine what would happen to your head if you banged into it hard enough to chip off thick potato chip-like pieces of wood. To put some numbers to this, a pro football player gets a concussion if a hit to his head reaches the level of 80 times the force of gravity. When the beak of a woodpecker hits wood, the impact is roughly 1,200 times the force of gravity. If that is the case, why do any pileated woodpeckers remain alive and with a functional brain?
This has intrigued a number of scientists. Their research has shown that woodpeckers, in general, possess several structural adaptations that keep their small brain intact despite their proclivity for the self-destruction of their brain. One is the bone structure of the skull, which is somewhat spongy in nature and, thus, a good shock absorber. Another is the tongue which, by wrapping around the brain, also acts as a very effective shock absorber. Having a small brain also helps, because there isn’t so much to be jostled.
The bottom line is that despite their seemingly unchanging appearance, our forests are anything but static. The intrinsic force for growth in our trees and plants is balanced by a variety of destructive forces, which keep the overall configuration of a mature forest looking pretty much the same. When you look more closely, a remarkably diverse set of mini-dramas underlies that seeming stability. Sometimes it is good just to get up close and keep your eyes open.