Sittidae – Nuthatches

The nuthatches constitute a genus, Sitta, of small passerine birds belonging to the family Sittidae. Characterised by large heads, short tails, and powerful bills and feet, nuthatches advertise their territory using loud, simple songs. Most species exhibit grey or bluish upperparts and a black eye stripe.

Most nuthatches breed in the temperate or montane woodlands of the Northern Hemisphere, although two species have adapted to rocky habitats in the warmer and drier regions of Eurasia. However, the greatest diversity is in Southern Asia, and similarities between the species have made it difficult to identify distinct species. All members of this genus nest in holes or crevices. Most species are non-migratory and live in their habitat year-round, although the North American red-breasted nuthatch migrates to warmer regions during the winter. A few nuthatch species have restricted ranges and face threats from deforestation.

They are omnivorous, eating mostly insects, nuts and seeds. They forage for insects hidden in or under bark by climbing along tree trunks and branches, sometimes upside-down. They forage within their territories when breeding, but they may join mixed feeding flocks at other times. Their habit of wedging a large food item in a crevice and then hacking at it with their strong bills gives this group its English name.

Nuthatches are compact birds with short legs, compressed wings, and square 12-feathered tails. They have long, sturdy, pointed bills and strong toes with long claws. They have blue-grey backs (violet-blue in some Asian species, which also have red or yellow bills) and white underparts, which are variably tinted with buff, orange, rufous or lilac. Although head markings vary between species, a long black eye stripe, with contrasting white supercilium, dark forehead and blackish cap is common. The sexes look similar, but may differ in underpart colouration, especially on the rear flanks and under the tail. Juveniles and first-year birds can be almost indistinguishable from adults.

The sizes of nuthatches vary, from the large Giant Nuthatch, at 195 mm and 36g to 47g to the small Brown-headed Nuthatch and the Pygmy Nuthatch, both around 100 mm in length and about 10g.

Nuthatches are very vocal, using an assortment of whistles, trills and calls. Their breeding songs tend to be simple and often identical to their contact calls but longer in duration. The Red-breasted Nuthatch, which coexists with the Black-capped Chickadee throughout much of its range, is able to understand the latter species’ calls. The chickadee has subtle call variations that communicate information about the size and risk of potential predators. Many birds recognise the simple alarm calls produced by other species, but the Red-breasted Nuthatch is able to interpret the chickadees’ detailed variations and to respond appropriately.

The species diversity for Sittidae is greatest in southern Asia (possibly the original home of this family), where about 15 species occur, but it has representatives across much of the Northern Hemisphere.