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.
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| 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.
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| © 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: shareitscience@gmail.com
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