Sitta carolinensis

The white-breasted nuthatch (Sitta carolinensis) is a small songbird of the nuthatch family which breeds in old-growth woodland across much of temperate North America. It is a stocky bird, with a large head, short tail, powerful bill, and strong feet. The upperparts are pale blue-gray, and the face and underparts are white. It has a black cap and a chestnut lower belly. The nine subspecies differ mainly in the color of the body plumage. Like other nuthatches, the white-breasted nuthatch forages for insects on trunks and branches and is able to move head-first down trees. Seeds form a substantial part of its winter diet, as do acorns and hickory nuts that were stored by the bird in the fall. The nest is in a hole in a tree, and the breeding pair may smear insects around the entrance as a deterrent to squirrels. Adults and young may be killed by hawks, owls, and snakes, and forest clearance may lead to local habitat loss, but this is a common species with no major conservation concerns over most of its range. The nuthatches are a genus, Sitta, of small passerine birds which derive their English name from the propensity of some species to wedge large insects or seeds into cracks, and then hack at them with their strong bills. Sitta is derived from sittē, the Ancient Greek for nuthatch, and carolinensis means 'of Carolina' in Latin. The white-breasted nuthatch was first described by English ornithologist John Latham in his 1790 work, the Index Ornithologicus. Nuthatch taxonomy is complex, with geographically separated species sometimes closely resembling each other. The white-breasted nuthatch has an appearance and contact call similar to those of the white-cheeked nuthatch, Sitta leucopsis, of the Himalayas and was formerly considered to be conspecific with it. A study published in 2012 showed that four distinct lineages were genetically isolated from each other and could represent different species, recognizable by morphology and song. A molecular phylogeny published in 2014 and including all main species' lineages within nuthatches concluded that the white-breasted nuthatch was more closely related to the giant nuthatch (S. magna) than to S. przewalskii, formerly regarded as possibly conspecific with it; S. przewalskii turned out to be basal in the family. Like other members of its genus, the white-breasted nuthatch has a large head, short tail, short wings, a powerful bill and strong feet; it is 13–14 cm (5.1–5.5 in) long, with a wingspan of 20–27 cm (7.9–10.6 in) and a weight of 18–30 g (0.63–1.06 oz). The adult male of the nominate subspecies, S. c. carolinensis, has pale blue-gray upperparts, a glossy black cap (crown of the head), and a black band on the upper back. The wing coverts and flight feathers are very dark gray with paler fringes, and the closed wing is pale gray and black, with a thin white wing bar. The face and the underparts are white. The outer tail feathers are black with broad diagonal white bands across the outer three feathers, a feature readily visible in flight. The female has, on average, a narrower black back band, slightly duller upperparts and buffer underparts than the male. Her cap may be gray, but many females have black caps and cannot be reliably distinguished from the male in the field. In the northeastern United States, at least 10% of females have black caps, but the proportion rises to 40–80% in the Rocky Mountains, Mexico and the southeastern U.S. Juveniles are similar to the adult, but duller plumaged. Like other nuthatches, this is a noisy species with a range of vocalizations. The male's mating song is a rapid nasal qui-qui-qui-qui-qui-qui-qui. The contact call between members of a pair, given most frequently in the fall and winter is a thin squeaky nit, uttered up to 30 times a minute. A more distinctive sound is a shrill kri repeated rapidly with mounting anxiety or excitement kri-kri-kri-kri-kri-kri-kri-kri; the Rocky Mountains and Great Basin subspecies have a higher, faster yididitititit call, and Pacific birds a more nasal beeerf.