Thursday, May 15, 2008


When we were leaving Lone Rock Point the other day, J found some woodpecker holes. We used to have woodpeckers in my yard when I lived in Connecticut about 10 years ago, and I remember vividly the hollow, rapid noises they made. Anytime I hear a woodpecker, I am transported back to the house we lived in: it's 6-acres of woods, ponds, streams and Mountain Laurel. The sound is almost haunting.

The woodpecker is beautifully adapted for pecking wood. From the skull to the tail feathers to the feet, woodpeckers have amazing adaptations that allow them to make holes in trees for nesting, feeding and even mating purposes.

The skull of the woodpecker is built to withstand multiple, rapid, high-impact collisions. The brain is encased tightly by the skull, with little cerebrospinal fluid, which keeps the brain from slamming into the skull interior with much force. The beak of the woodpecker is separated from the skull by a spongy matrix of bone, which absorbs shock. Additionally, the hyoid apparatus of the woodpecker has been shown to reduce shock to the brain.

The hyoid apparatus consists of bone and cartilage and controls the movement of the woodpecker's tongue. Muscles anchor the apparatus to the base of the skull and the apparatus extends behind the skull base up around the skull, sometimes as far as the nasal cavity. When the muscles anchoring the apparatus are engaged, the tongue can be extended as far as 1.5 times the length of the woodpeckers beak. This allows the woodpecker to reach far into holes in trees to grab insects and their larvae. The tongue of the woodpecker is also adapted for grubbing (hah!) in that it is rigid and barbed...perfect for spearing!

The 4th digit on the woodpecker's foot has a large range of motion, able to sit at a near-90 degree angle to the other digits. Combined with long stiff, tail feathers, the grasping capability of the woodpecker's feet allow the woodpecker to remain stable.

The anatomy of the woodpecker skull has been a source for the denial of evolution, but I can't imagine a more perfect example of evolution!


Ryan, Rusty. Anatomy and Evolution of the Woodpecker's Tongue.

L. J. Gibson (2006) Woodpecker pecking: how woodpeckers avoid brain injury Journal of Zoology 270 (3) , 462–465 doi:10.1111/j.1469-7998.2006.00166.x

Juhachi, ODA. (2006) Mechanical Evaluation of the Skeletal Structure and Tissue of the Woodpecker and Its Shock Absorbing System. JSME International Journal. Series A. Solid Mechanics and Material Engineering (Japan Society of Mechanical Engineers). 49; 3. 390-396


Zach said...

Woodpeckers rock! We get several varieties up here, and they're suprisingly tolerable of people.

rafcosford said...

would the learned person tell me how many woodpeckers died whilst trying to 'evolve' into the perfect creation they are for how they feed, ie, bent beaks, fractured skulls etc.

Amanda said...

Well, certainly woodpeckers weren't "trying" to evolve. Evolution isn't a choice that organisms make.

And you have mistaken how evolution works. There is no specific end goal. Evolution doesn't seek to accomplish any specific thing. So, woodpeckers weren't slamming their heads into trees, attempting to become what they are now. Simply, the woodpeckers with features that aided in their survival out-reproduced those that didn't have those features. And those changes in who survived and passed on their genes and who didn't, slowly resulted in what we see today.

rafcosford said...

so let me get this straight, the woodpecker grew a long tongue [with nowhere to store it safely] & also knew what to do with it. Then sat down with its offspring & told them that one of them would have to find a way of storing the tongue. Remember that you have already stated that organisms have no choice. So how did they know which route to tke before all of them died?

Amanda said...

Hmmm. No, you don't have it straight. That's definitely not what I said!

No woodpecker grew a long tongue with nowhere to store it...a woodpecker with a deformity like that probably wouldn't have survived long enough to pass on its genes. And no woodpecker would have "told" its offspring that they would have to store a tongue.

First, it's not necessarily the tongue that is elongated. It's the hyoid apparatus that allows the tongue to protrude. Second, you're assuming that the evolution of these hyoid apparatuses happened over one or two generations. Likely, this happened over a VERY long time.

I think that your understanding of evolution is very flawed. I don't have the expertise or the time to explain to you what it is that you're missing - but there are some great books out there that describe the process very simply. In fact, if you just pick up a college biology textbook, you will get the very basic information that you need to understand how evolutionary adaptations (such as the woodpecker's hyoid apparatus) could form.

Amanda said...
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