The beautiful nuthatch (Sitta formosa) is a bird species in the family Sittidae, collectively known as nuthatches. It is a large nuthatch, measuring in length, that is not sexually dimorphic. Its colour and markings are dramatic, the upper parts being black and azure, streaked with white and pale blue on the head and lined with the same colours on the wing feathers. The are orange, and the and are ochre. An irregular, dark highlights its eye. Its ecology is not fully described, but it is known to feed on small insects and larvae found on the trunks and epiphyte-covered branches of trees in its range. Reproduction takes place from April to May; the nest is placed in the hole of an oak, rhododendron, or other large tree. The nest is made of plant material and fur in which the bird typically lays four to six eggs.
Although the species is found in most of the countries making up the mainland of Southeast Asia, it appears to be rare throughout its range, its population being highly local where it is found. The bird nests predominantly in montane forest at an altitudinal range from up to nearly , with some seasonal height adjustment, down to around in winter. Its localised occurrence within its range makes rigorous estimates of its population difficult, but its habitat is threatened by deforestation and the species appears to be in decline. It has been classified as vulnerable by the International Union for Conservation of Nature.
Taxonomy
left|thumb|Beautiful nuthatch in Arunachal Pradesh, India
The nuthatches constitute a genus Sitta of small passerine birds in the family Sittidae, typified by short, compressed wings and short, square 12-feathered , a compact body, longish pointed , strong toes with long claws, and behaviourally, by their unique head-first manner of descending tree trunks. Most nuthatches have grey or bluish and a black eyestripe. Sitta is derived from the Ancient Greek name for nuthatches, , sittē. "Nuthatch", first recorded in 1350, is derived from "nut" and a word probably related to "hack", since these birds hack at nuts they have wedged into crevices. The genus may be further divided into seven subgenera, of which the beautiful nuthatch is placed alone in Callisitta (Bonaparte, 1850), and the species was therefore sometimes called Callisitta formosa. Its kinship with other members of the genus is unclear. The bright blue colour of its invites a comparison to the blue nuthatch (S. azurea), or other blue-tinted nuthatch species such as the velvet-fronted nuthatch (S. frontalis), yellow-billed nuthatch (S. solangiae) and the sulphur-billed nuthatch (S. oenochlamys), but its distribution being focused in the eastern Himalayas, and the uniqueness of its plumage, argues against the assumption. No subspecies have been identified.