The Incredible Articulating Pinky

Pileated Woodpecker with digit #4 rotated for a better grip

Can you say ‘zygodactyl’ three times, fast?

You learn the most interesting things when your bedtime reading is the Peterson Reference Guide to Woodpeckers. My most recent discovery is about woodpecker feet. I already knew that most woodpeckers have zygodactyl feet: Two toes face forward. Two toes face backward. That toe arrangement gives them superior grip strength when clinging to a tree trunk. Their massive claws help, too.

What I did not know is that the multi-talented woodpecker has articulating pinkies.

Zygodactyl is not the classic bird-toe configuration. Songbirds have a more familiar toe arrangement, with three toes facing forward and one pointing to the rear. Called the anisodactyl foot, it’s useful for basic perching. Ducks have webbed feet for obvious reasons. Emus have only three toes, and I cannot speculate what advantage that gives them.

But back to my surprising avian anatomy discovery. I say surprising, because I have logged hundreds of hours watching and filming woodpeckers, but I never noticed that they have an articulating toe on each foot. A woodpecker can rotate its outermost rear toe more than 90 degrees until it points forward in songbird fashion. The rotating toe is officially named digit #4 (I’m not making that up…the toe numbering system is explained on page 182 of the Handbook of Bird Biology, my other light reading). For simplicity, I just call it the articulating pinky.

Diagram of a woodpecker's left foot. Each foot has one toe that can rotate forward.
A woodpecker’s left foot. Each foot has one toe that can rotate forward.

I reviewed a lot of my video footage to find the articulating pinky in action, and I found that most of my videos catch the birds with their back toes out of view, under their bodies. But here’s a clip that shows the different toe positions. It would have been nice if the bird had chosen a darker tree on which to highlight his gray toes, but if you look closely, you’ll see the before-and-after toe positions.

When a woodpecker needs to get a better grip, he just rotates one or both of his pinkies. Don’t say you didn’t learn anything fascinating this week. Whether this is useful new knowledge…you decide.

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