This American Pipit is having some trouble holding on to the slippery stem of a dried fennel bush on the Open Circle Viewpoint in the northeast corner of the park. Its stumbling doesn’t make sense at first glance. The pipit is one of a small number of species with an extra-long hind claw. In bird anatomy, the claws are its toes, and the hind toe is analogous to our big toe. It’s called the hallux. About 60 percent of all bird species have their toes arranged in this pattern: three toes pointing forward, the hallux pointing back. (This pattern is called anisodactyly.) This pattern is adapted for perching on a twig, and this ability defines the passerine order — birds that perch. Most passerines also have a set of tendons in their ankles that automatically lock the toes’ grip when the legs are bent. Thanks to this feature, the birds can go to sleep without falling off their perch. So then, why does this American Pipit have so much trouble holding on to its perch? I don’t know the answer, but I suspect it has something to do with that elongated hallux. You might think that being longer, it would help him lock on to thicker branches. But expert opinion suggests that the long hallux is an adaptation for ground walking. The pipit breeds in the grasses and marshes of arctic tundra and in mountains above the tree line. Not much to perch on, there. It nests on the ground in patches where the snow has recently melted. The long hind toe, it’s believed, gives it more traction on soft surfaces. Note that the pipit walks one leg at a time, the way humans do, and doesn’t hop the way most ground-pecking birds do. The few other species with an elongated hallux, called the longspurs, are also ground dwellers. Bottom line, the pipit’s extended hallux doesn’t have the strength of grip required for secure perching.
That, or this pipit was a bit of a klutz, or had been eating too many fermented berries.