This week's science observation comes from my Dad. He recently caught a Pileated Woodpecker in action on a tree nearby my childhood home. Impressed at how hard it was hammering on the tree, we thought it would be interesting to learn more about woodpecker physics.
At 15-19 inches long, the Pileated Woodpecker is the largest extant woodpecker in North America. There are some birders who still hold out hope that the larger Ivory-billed Woodpecker still lives. However, after an extensive study in the Southern U.S. following a sighting of this long thought to be extinct bird in 2005, no definitive evidence of their existence was found. The Pileated Woodpecker is the "Woody Woodpecker" of the family, with a shockingly bright red crested head, and a large black body with bold white stripes. These woodpeckers have large territories and are rarely seen with many others of their kind, besides their mate. If you have heard or seen one of these amazing woodpeckers banging on a tree to forage or create a nesting cavity, you cannot help but be impressed.
So how do they hammer so hard and fast against a tree trunk and not sustain brain injury? The woodpecker's head hits with the force of about 1,000 g's. This is like a human hitting their head on a wall at about 16 mph. They can do this up to 20 times per second! There are several adaptations that allow these birds to operate unscathed. They maximize the space in their skull around their small brain. Because any dead space is at a minimum, their brain does not have room to jostle about. The woodpecker's long tongue is stored back up and around its skull to just under the skin of its forehead area. The tongue provides some extra shock absorption for the brain as well. See a diagram of this incredible tongue here.
Their beak is constantly being sharpened, and this acts as a sharp chisel when hammering on a tree trunk or log. In order to hit the target with such force, the bird uses its strong neck muscles to pull back from the tree, then pulls forward with their feet to increase the force of their strike. Another "safety feature" is the nictitating membrane. This is essentially a third eyelid that is pulled across the eye just before the woodpecker strikes. This membrane swells and protect the eye from the force and pressure of the blow. An added bonus of the membrane is keeping debris away from the eyes as wood chips fly away from the tree.
|Pileated Woodpecker ©Dean Benton 2015|
Using some high tech equipment, Chinese scientists studying the Great Spotted Woodpecker found that miniscule modifications in the bird's skull structure between the skull and the lower mandible allow a bit of sliding that help to absorb impact. Also discovered in this study was that the bone structure of the lower beak is longer than the upper beak, whereas the tissue covering the upper beak is longer than the layer on the lower beak. The tissue and bone mismatch is thought to divert energy through the lower beak and therefore away from the brain. If you'd like to read the study you can find it in full text here.
Pileated Woodpeckers use these fantastic adaptations to forage for food, such as carpenter ants and beetle larvae. They create long, rectangular holes in trees, rather than round. Sometimes they carve out so deeply into a dead tree that it cracks the tree in half! You most often will find them in areas with mature deciduous, or mixed deciduous-coniferous forests. They will also eat berries and visit suet and bird seed feeders.
These big birds also carve out rectangle shaped cavities in dead trees to raise their young. They do not build a nest inside the cavity, rather it is lined with wood chips from the excavation. The male and female care for the 4 eggs that are generally laid in a clutch. These birds will "mate for life" so to speak, and stick together unless one dies. In that case they will find a new mate if possible. In addition to their sometimes raspy, piping calls they will communicate with one another by drumming on trees.
|© Dean Benton 2015|
If you are lucky enough to view one of these in the wild, you will most likely hear it before you see it! If you are interested in learning more about common woodpeckers in the Northeast, check out my post: See it? Share it! GBBC and Woodpeckers Galore! Do you have a woodpecker experience to share? Tell us about it in the comment section or e-mail me at: firstname.lastname@example.org