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Nuthatch – a small woodland songbird with a habit of jamming seeds into crevices and then hacking them open as if its beak were a hatchet, hence, presumably, the name “nuthack,” which evolved into “nuthatch.” There are 28 nuthatch species worldwide. The species in Evanston are the White-breasted and the Red-breasted. The White-breasted Nuthatch is a reliable year-round resident, preferring deciduous or mixed woodlands and woodland edges with large old trees, such as in Perkins Woods. It ranges throughout most of the United States, southern Canada and central Mexico. The smaller Red-breasted Nuthatch is a species of the northern coniferous forests and is found in Alaska and western Canada as well as the U.S. and Mexico. They “irrupt” here irregularly, apparently when the cone-crop is scarce farther north.
The White-breasted Nuthatch is a handsome bird with its snow-white breast, white throat, and its black eye contrasting with its white face. Its black cap extends from its bill to its grey-blue back. Its darker grey wings and tail are edged in black, and a chestnut-colored patch shows under its tail and on its flanks. This compact, agile little bird, a trifle smaller than a house sparrow, has a very short tail, a long straight black bill, and black legs. The female has a lighter grey crown; otherwise, the sexes are identical.

Nuthatches are those unique and remarkable birds who walk upside down on tree trunks and branches in a zig-zag motion while probing crevices in bark for food. Their strong beaks chisel away bark to reveal seeds or insects. When a nuthatch pauses on its way down, it thrusts its head and neck outwards at what appears to be almost a 90 degree angle to the trunk. Their nasal call “yenk yenk yenk yenk” keeps them in contact or warns of danger as they feed and has been likened to the sound of a fast-squeezed bathtub toy. Writers speculate that coming from the opposite direction of woodpeckers and creepers, they find those nuggets that others miss. Unlike woodpeckers, who depend upon long stiff tail feathers for support and balance while climbing up, nuthatches can cling head-down by using the long, strong sharp decurved claw on its hallux (back) foot and strong, deeply curved front claws, giving them a good grip on any bark surface. (They also walk upright around trunks and on branches.)

White-breasted Nuthatches are monogamous and live in a 10 to 25-acre territory in which they mate, feed and breed, using only a half-acre for breeding. They cache food in crevices all over their territory, a single morsel per space. They may disguise those morsels with bark or lichens. During fall, they cache “mast”: acorns, beechnuts, hickory nuts, even cherry pits, which they retrieve in winter. If eating a seed right away, they carry it off from a feeder, stuff it into a cranny, then pound away at it with their strong beaks to get at the heartmeat, instead of holding it between their feet like a chickadee. During spring and summer, they eat insects, including spiders, caterpillars, beetles, flies, grasshoppers, larvae of gypsy moths and weevils, many of which are forest pests. They feed their young exclusively on insects. They forage in mixed flocks with chickadees and others, counting upon those chattering birds to chase away predators.

The nuthatch couple, having foraged independently after breeding season, come together early in the new year and stay close together while courting and raising young. Dawn on a chilly January morning finds the male on a conspicuous perch repeatedly giving his loud “wer wer wer” song. He will bow deeply, sway back and forth, raise his head and tail and droop his wings, all of which to attract his nearby mate. Then the pair go off to feed together for the day, keeping in touch by soft calls. Some weeks later, the male begins to offer food to his mate. At night, each nuthatch roosts alone in its own hole no matter what the weather.

The female builds the nest in a tree in a large natural cavity such as a knothole or an old woodpecker nest. She makes a cup of bark fibers, grasses, twigs, roots, hair and fur. She incubates an average clutch of seven eggs for about 12 days, while her mate brings her food. Both sexes feed the nestlings for 14 days and continue feeding their fledglings for another two weeks. They nest once a season and may re-use the nest in a following year.

Perhaps because their natural cavity nests are in competition from squirrels, chipmunks and other cavity-nesting birds, nuthatches exhibit two unusual nest protection strategies: bill-sweeping and distraction displays. Bill sweeping involves sweeping the entrance and the interior from side to side with an insect, often a beetle, or occasionally a plant. Sweeping goes on all during nesting season whenever the need arises. No one has yet explained the purpose of bill-sweeping, but scientists speculate that the materials’ chemical secretions deter predators. One nuthatch was reported to have used strong-smelling nicotine-laced cigarette butts for the majority of her nest. Distraction displays occur when a predator approaches the nest. A nuthatch will spread its wings and tail, point its bill upward and sway, like a very slow metronome pendulum.

In winter, providing water plus high-calorie foods such as black oil sunflower seed, peanut butter and suet will easily attract nuthatches to a feeder and help them survive harsh weather.

Birrrrrrrds in Winter

Birds have to adapt to extreme heat and cold, whether they are year-round residents or migrants. Even during the warm breeding season, hot or cold spells can kill. Each bird species has its own behavioral and physiological adaptions to temperature extremes.Winter days are short and birds must eat more in less time in order to maintain their metabolism.  Putting on much extra fat isn’t an option, because they can’t exceed a particular weight in order to fly. Night is more a problem than day.Birds are warm-blooded and their temperatures are typically 105 degrees. Their challenge is to maintain that temperature when outside temperatures fall.  Small birds like the White-breasted Nuthatch are particularly vulnerable because they have a high surface (outside) to volume (inside where metabolism takes place) ratio. Behaviorally, some birds fluff up feathers to trap tiny pockets of warm air as insulation. Other species ball themselves up and stay stock still.  Birds often retreat to some sort of cover. Some species such as juncos huddle together in dense brush, making themselves almost into one large organism (lower surface to volume ratio) each bird jockeying for position during the night to get into the middle. Bare parts such as bills and legs are particularly vulnerable and must be protected by feathers – pulling one leg under cover while standing on the other and by tucking in its bill. Some birds sit down on both legs so that the legs and feet are included in the ball. From this position – luffed into a ball and down on two legs – they are in vulnerable take-off position for escaping predators.Physiologically, heat exchange occurs in the bare legs of many birds.  Leg veins and arteries are close to each other and the warm blood leaving the core of the body transfers its heat to the cold blood returning from the feet. Some birds can constrict the amount of blood flow to the feet at low temperatures, allowing gulls, for example, to stand on ice. Geese grow extra down feathers. Birds can drop their internal temperatures below their daytime temperatures and survive the night by entering “torpor” or near-torpor states. They thermoregulate their bodies, but depending upon the degree of torpor, being aroused from this state takes energy and birds must eat immediately. During torpor, birds are especially vulnerable to predators.  Another metabolic strategy is the modification of internal tissues to generate shivering. If you see a shivering bird, respect that internal mechanism and do not feel you have to run out and cover it with a blanket. It is a natural protective adaptation.

Libby Hill

Libby Hill is the author of "The Chicago River: a Natural and Unnatural History. She has been writing about birds and trees and Evanston's natural history for the Roundtable since 2004.