Get to know the birds that cling

Among the numerous amazing abilities of birds, there is one superhuman talent that is clearly their most striking trait: flying. But surrounded as we are by all these flying swifts and swallows, finches and falcons, it’s easy to overlook another means of avian movement that is similarly beyond our capacity: the ability to cling to surfaces of every orientation, traversing tree trunks and the undersides of branches with the ease with which we walk along the level ground. Not all birds can defy gravity in this way, even without the use of wings, but three local families can: woodpeckers, creepers and nuthatches.

Of these three groups of clinging birds, the most well-known are the woodpeckers. The majority of our local species bear a number of similarities: black-and-white bodies, often with red on the crowns — especially in males — and habits of feeding on the trunks, bark and branches of trees. While most of our small woodland birds belong to the passerine or songbird order, woodpeckers are from a quite distinct evolutionary lineage. This is most evident in the structure of their feet, which feature two forward-facing toes and two backward-facing toes in contrast to the typical three-and-one arrangement of songbirds, and in their unique use of their tails, stiffened and strengthened to provide an additional point of support on vertical surfaces.

The woodpeckers have those unique adaptations of feet and tail to allow access to the surface of trunks and large tree limbs. Once they get there, their story gets even stranger, with bills designed as chisels, brains cushioned for repeated hammering with those bills and extravagantly long and sticky tongues for probing into insect holes and tunnels. It’s easy to look up into an oak tree, spot half a dozen songbirds and a woodpecker and lump them all together under the undiscriminating label “birds.” But woodpeckers are stranger than the rest, diverging long, long ago toward their weird and inimitable lifestyle of bashing tree trunks with their beaks.

Which is not to say that no songbirds are capable of skillful clinging. Two families in particular stand out: creepers and nuthatches. Creepers are particularly easy to overlook, represented locally only by the discreet and well-camouflaged brown creeper. Creepers share some methods of their approach with woodpeckers — they use their tail as an important support, meaning they, like woodpeckers, can only travel in an upward direction. In fact, creepers are even more dedicated “ascenders” than woodpeckers, with their characteristic feeding style involving flying to the base of a tree, creeping upward while looking for insects and spiders, and then flying to the base of the next tree to repeat the process. But they are entirely unrelated and obviously different in other respects, such as their bills, which are long, thin and curved — tools for probing into crevices rather than for pounding and hammering.

The last of our master clingers are nuthatches, a more familiar group with three local representatives: the white-breasted, red-breasted and pygmy nuthatches. While creepers creep upward, the Spanish name for nuthatch is “bajapalos,” which I like to render as “pole goer-downer.” They can and do frequently travel headfirst down tree trunks, as well as in every other direction, an ability that indicates their different approach to the clinging life. Nuthatches do not use their tail to prop themselves away from the trunk, but instead splay their feet apart, two powerful grippers armed with oversized rear toes that clutch the bark like squirrel feet.

Of our three nuthatch species, the red-breasted and pygmy are relatively less common locally, favoring coniferous trees. White-breasted nuthatches, in contrast, love oaks trees, especially the deciduous species like valley and blue oak, which have deep furrowed bark in which insects and other arthropods can hide or lay their eggs. With their unique clinging ability and long beaks, white-breasted nuthatches can access areas that are off-limits to many other birds. With their ability to climb downward, they spot hiding places that their upward-traveling rivals, the woodpeckers and creepers, often miss. And with each tree converted into their private library of vast and secret shelves, the nuthatches store food in these areas as well, seeds and scraps of acorns lodged where only they can go.

Jack Gedney’s On the Wing runs every other Monday. He is a co-owner of Wild Birds Unlimited in Novato and author of “The Private Lives of Public Birds.” You can reach him at jack@natureinnovato.com.