Nuthatches must be the geckos of the bird world. They routinely comb the crevices of the bark from a head-down perspective and explore the underside of branches while hanging upside down. I watched one little White-breasted Nuthatch do just that, and wondered why they do it. What advantage is it to look at the world upside down?
Quite a lot actually. Chickadees, Brown Creepers, and multiple species of Woodpeckers typically explore the convoluted landscape of tree bark from the head-up perspective, which allows the bird to see small food items on top of a section of bark. But what little critters might be hiding on the bottom of that same section? Head-up foragers would miss it, because they can’t see beneath the bottom overhang. But foraging upside-down brings that whole perspective into focus. And all four North American nuthatch species exhibit this unusual behavior.
But how do they hang on, upside down? They don’t have toes like geckos or tree frogs with suction cups on their toe pads. Nuthatches don’t have the two forward-two back foot construction like woodpeckers, nor do they have the woodpeckers’ stiff tail feathers to help prop them up against the tree. Instead, nuthatches have elongated toes, with substantial claws that help them cling to crevices in three bark. Check out the feet of the bird in the photo below.
Here’s a White breasted Nuthatch foot to illustrate the toe adaptation. The toe on the right is equivalent to the hallux (big toe). It can be mobilized to the side or the rear to grip the surface; the enlarged claw no doubt provides greater gripping strength when the bird is hanging upside down.
(Photo from www.hiltonpond.org — Nuts about Nuthatches, Nov 2007)
White-breasted Nuthatches are year-round residents where they occur in the U.S., which includes some far northern residents that tolerate the brunt of frigid, cold winters. Like other avian insectivores that overwinter in harsh climates, nuthatches supplement their diet with seeds, suet, and berries, but prefer a little “meat” when they can find it.
I love the way these little guys bend their heads around to look at you from their upside down position. It’s like some kind of extreme yoga back-flex pose.