The ‘upside-down bird’ is a natural acrobat

SPRINGHOUSE FARM JOURNAL

By Heather Lovett
   I once heard about a scientific study in which the subjects were asked to wear contraptions over their eyes that made them see the world upside down. The sensation must have been disorienting, to say the least, but eventually the volunteers were able to adapt reasonably well and perform ordinary tasks. When the project was over they went through an equally dizzying period of readjustment as they returned to their rightside-up lives.
   I thought of those hapless study subjects recently as I watched a white-breasted nuthatch approach our birdfeeder in typical nuthatch fashion, landing at the top of the pole and working its way down, headfirst, to the perch. It accomplishes this feat by placing one foot forward and one foot behind, using the claws of the rear foot to cling with, and the forward foot as a brace. Nuthatches are nicknamed "upside-down birds" because of this unique skill.
   Unlike the people in the scientific study, however, they are able to navigate rightside up, upside down, and sideways with ease, never losing their balance. Foraging a tree trunk, they inspect every square inch, it seems, with a fine-toothed comb. (The brown-headed nuthatch actually does use a tool, although not a comb; it holds a small piece of bark in its bill, poking and prodding away loose bits to uncover hidden insects.)
   Nuthatches eat mostly insects, but in winter they supplement their diet with seeds, often stashing them in bark crevices for future use. Lacking a stout, nut-cracking beak like a finch, the nuthatch has developed a special system for eating seeds, easily observed at birdfeeders. It will grab a single seed, fly off to a tree, and cram it into a convenient crevice, where it hammers away at the seed to get out the meat. This "hatching" (i.e. "hacking") behavior is responsible for the bird’s name.
   White-breasted nuthatches are year-round residents in our area, although I see them mainly in winter when they come to our feeders. They are handsome birds with a formal look about them, rather like miniature penguins. Stocky and short-tailed, the male has a sleek black cap (the female’s is dark gray), a slate-blue back with elegant black-and-white trim, and a snow-white breast. Its face is white as well, with beady black eyes and a long, sharp bill.
   The red-breasted nuthatch is a smaller bird, easily distinguished by its rusty breast, black stripe through the eye, and no black-and-white markings on its wing or tail feathers. Although normally found farther north in conifer forests, red-breasted nuthatches will sometimes migrate south in large numbers when winter food supplies are scarce.
   Two other species live in the United States, the brown-headed nuthatch of the Southeast and the pygmy nuthatch of western pine forests. Similar in appearance and behavior, they are more sociable than other nuthatches, often traveling in groups and sharing household duties.
   Nuthatches are cavity-nesters, some excavating their own holes, and others, like the white-breasted nuthatch, finding existing holes in which to raise their young. Competition among bird and animal species for nesting sites can be fierce, and is exacerbated by forest depletion and the introduction of alien species like starlings and house sparrows.
   Nesting boxes have gone a long way towards helping some birds adapt to these changes (the Eastern bluebird is a good example), but while nuthatches will occasionally use boxes, they prefer a more natural site. Populations of white- and red-breasted nuthatches seem to be holding steady, however, and their success may have something to do with ingenious tactics practiced around their nesting sites.
   The white-breasted has been observed with a crushed insect in its bill, wiping methodically around the entrance hole to its nest. Bird experts speculate that the dead-beetle scent might keep rivals and predators away. The red-breasted’s deterrent of choice is pine pitch, which is smeared in a similar fashion around the nest opening. The parents are savvy (and small) enough to fly straight in, but intruders are likely to get stuck.
   I’ve noticed that nuthatches often arrive at our feeder in pairs, one male and one female. I can tell when they are around because of their nasal "ank ank" call, like the tooting of a little tin horn. They are monogamous birds, staying with the same mate during the breeding season, and they typically begin pairing off in winter, earlier than most other birds.
   Watching these little acrobats at work, I wonder what it might be like living the upside-down life of a nuthatch. Short of becoming a trapeze artist, or signing up as a volunteer for a study on visual perception, I guess I will never know. I can only marvel at the way they seem perfectly adapted to life in a tree, moving up, down, and around with the greatest of ease, making it look like the most natural thing in the world.
   Reference: Sibley, David Allen. "The Sibley Guide to Bird Behavior." New York: Alfred A. Knopf, 2001.