nuthatch, common name applied to a number of Old and New World species of small birds of the genus Sitta, related to the titmouse and the creeper. The name refers to its habit of wedging nuts into crevices in trees and pecking them open. Nuthatches are unique in that they climb down tree trunks headfirst in their search for insects and spiders. Unlike the creepers, the nuthatches have straight bills and do not use their short tail feathers as a prop. Nuthatches are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Passeriformes, family Sittidae.

Any of about 22 species (genus Sitta, family Sittidae) of songbirds that are 4–7.5 in. (9.5–19 cm) long and have a short, square tail, short neck, and thin, pointed bill. Most are forest dwellers; some live in rocky areas. Nuthatches search tree trunks and rocks for insects, often descending headfirst. They also eat seeds, which they may store for winter. The nest is a grass- or hair-lined cavity. Nuthatches are most common from Eurasia to Japan and southward; four species occur in North America. Most are bluish above and white or reddish below; there may be a black eye stripe or a cap.

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