Thursday, June 20, 2024

A white-breasted nuthatch climbs headfirst down a tree in North Cambridge. (Photo: Richard George)

The white-breasted nuthatch is a small bird about 6 inches long that is sometimes mistaken for a small woodpecker but for one distinguishing feature: It hops down tree trunks head first like a squirrel. Since squirrels have four legs with which to descend, the nuthatch seems as if it has the harder task. As Neltje Blanchan wrote in 1907 about these acrobatic birds:

Hanging fearlessly from the topmost branches of the tallest pine, running along the underside of horizontal limbs as comfortably as along the top of them, or descending the trunk head foremost, these wonderful little gymnasts keep their nerves as cool as the thermometer in January. From the way they travel over any part of the tree they wish, from top and tip to the bottom of it, no wonder they are sometimes called Tree Mice. Only the fly that walks across the ceiling, however, can compete with them in clinging to the underside of boughs.

A nuthatch finds an insect in June 2020. (Photo: Richard George)

White-breasted nuthatches probe bark crevices and chip away bark looking for food. During the summer, they eat mostly insects and spiders, but during the winter, they must rely more heavily on seeds and nuts. When a nuthatch finds a sunflower seed or an acorn, it wedges the seed into a tree crevice and hammers at it with its bill until the shell opens. Hence the name nuthatch, a reference to this shell-hacking behavior.

Most people think of birds as either being migratory or nonmigratory, but nuthatches can be either. Trees produce nuts, such as acorns, in different quantities each year. Some years, called mast years, trees produce abundant quantities of nuts – and in those years white-breasted nuthatches do not migrate, because there are plenty of nuts and seeds to eat throughout the winter. In other years, when trees do not produce many nuts, white-breasted nuthatches may migrate away from their home range, but in every direction, not just south. In fact, sometimes they even migrate north!

A white-breasted nuthatch in Huron Village makes a kank-kank-kank call. (Photo: Richard George)

In winter, white-breasted nuthatches join up with other birds in their territory to create a mixed flock called a foraging guild. They nuthatches know the alarm calls of the other birds (and vice versa), so individual birds do not have to spend as much time looking for danger and can concentrate more of their efforts on finding food. When a pair of nuthatches reaches the edge of its home territory, they drop out of the guild and a nuthatch pair in the new territory joins.

In late winter, breeding behavior begins. As Edward Howe Forbush said of nuthatches in 1929: “As spring approaches, the male … becomes very gallant and attentive to the female and even shells seeds for her and passes her the freed kernels.” The pair chatters back and forth emitting a nasal kank, kank, kank, kank.

White-breasted nuthatches often take a single sunflower seed from a bird feeder, wedge it into a tree and peck it until it opens. (Photo: Richard George)

Nuthatches nest in existing tree cavities. Before preparing the nest, some female nuthatches will wipe the inside and outside of the cavity with a crushed insect, such as a beetle that exudes a pungent oil. It is not known why they do this, but some think the chemical secretions may help repel predators. The female then lines the nest cavity with tree bark. According to William Brewster in 1936: 

The female … would run out on a large branch, pry off a scale of bark 5 or 6 inches long, take it into the hole and almost instantly reappear and go after another. The male occasionally got one and simply poked it into the hole, without entering himself.

A white-breasted nuthatch in Coolidge Hill. These birds weigh only about as much as four nickels – 0.7 ounces. (Photo: Richard George)

On top of the bark, nuthatches construct a cup-shaped nest of small strips of bark, grasses, and other soft materials. On top of this they place fur, feathers or hair. As Lucien Harris noted about a pair of nuthatches in 1927: 

This unique pair discovered a dead rabbit – one that had been dead for some time – and proceeded to line the nest proper … with rabbit fur, so that when completed the box smelled more like a buzzard’s domicile than a nuthatch’s home. 

A nuthatch forages in Strawberry Hill in January. (Photo: Richard George)

When the nest is complete, the female lays about six eggs and incubates them for about 12 days. The male does not help incubate the eggs, but he does find food that he brings to the female on the nest. When the chicks hatch, both parents feed the youngsters, who fledge about 26 days later. Young birds do not return to the nest cavity to sleep; instead they may cling upside-down to the tree trunk underneath a branch.

As you are out and about this winter, keep your eyes peeled for white-breasted nuthatches. You might spy one of these fascinating birds as they climb up and down tree trunks in search of food.

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Jeanine Farley is an educational writer who has lived in the Boston area for more than 30 years. She enjoys taking photos of our urban wild things.