Солтүстік жарты шардың ағашқарғалары

Genus, Sitta, of small passerine birds from the Northern Hemisphere

The nuthatches (/n//ʌ//t//.//h//æ//tʃ///) 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. Nuthatches 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.

The nuthatch family, Sittidae, was described by René Primevère Lesson in 1828. The wallcreeper is intermediate in its morphology between the nuthatches and the treecreepers, but its appearance, the texture of its plumage, and the shape and pattern of its tail suggest that it is closer to the former taxon. The nuthatch vanga of Madagascar (formerly known as the coral billed nuthatch) and the sittellas from Australia and New Guinea were once placed in the nuthatch family because of similarities in appearance and lifestyle, but they are not closely related. The resemblances arose via convergent evolution to fill an ecological niche. The nuthatches' closest relatives, other than the wallcreeper, are the treecreepers, and the two (or three) families are sometimes placed in a larger grouping with the wrens and gnatcatchers. This superfamily, the Certhioidea, is proposed on phylogenetic studies using mitochondrial and nuclear DNA, and was created to cover a clade of (four or) five families removed from a larger grouping of passerine birds, the Sylvioidea.

The nuthatches are all in the genus Sitta Linnaeus, 1758, a name derived from σίττη : síttē, Ancient Greek for this bird. The English term nuthatch refers to the propensity of some species to wedge a large insect or seed in a crack and hack at it with their strong bills.

Species boundaries in the nuthatches are difficult to define. The red breasted nuthatch, Corsican nuthatch and Chinese nuthatch have breeding ranges separated by thousands of kilometres, but are similar in habitat preference, appearance and song. They were formerly considered to be one species, but are now normally split into three and comprise a superspecies along with the Krüper's and Algerian nuthatch. Unusually for nuthatches, all five species excavate their own nests. The Eurasian, chestnut vented, Kashmir and chestnut bellied nuthatches form another superspecies and replace each other geographically across Asia. They are currently considered to be four separate species, but the south Asian forms were once believed to be a subspecies of the Eurasian nuthatch. A recent change in this taxonomy is a split of the chestnut bellied nuthatch into three species, namely the Indian nuthatch, Sitta castanea, found south of the Ganges, the Burmese nuthatch, Sitta neglecta, found in southeast Asia, and the chestnut bellied nuthatch sensu stricto, S. cinnamoventris, which occurs in the Himalayas. Mitochondrial DNA studies have demonstrated that the white breasted northern subspecies of Eurasian nuthatch, S. (europea) arctica, is distinctive, and also a possible candidate for full species status. A 2006 review of Asian nuthatches suggested that there are still unresolved problems in nuthatch taxonomy and proposed splitting the genus Sitta. This suggestion would move the red and yellow billed south Asian species (velvet fronted, yellow billed and sulphur billed nuthatches) to a new genus, create a third genus for the blue nuthatch, and possibly a fourth for the beautiful nuthatch. The fossil record for this group appears to be restricted to a foot bone of an early Miocene bird from Bavaria which has been identified as an extinct representative of the climbing Certhioidea, a clade comprising the treecreepers, wallcreeper and nuthatches. It has been described as Certhiops rummeli. Two fossil species have been described in the genus Sitta: S. cuvieri Gervais, 1852 and S. senogalliensis Portis, 1888, but they probably do not belong to nuthatches.

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. Nuthatches 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. to the small brown headed nuthatch and the pygmy nuthatch, both around in length and about
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.

Some nuthatches, such as the Eurasian nuthatch and the North American species, have extensive ranges and large populations, and few conservation problems, although locally they may be affected by woodland fragmentation. In contrast, some of the more restricted species face severe pressures. The endangered white browed nuthatch is found only in the Mount Victoria area of Burma, where forest up to above sea level has been almost totally cleared and habitat between is heavily degraded. Nearly 12,000 people live in the Natma Taung national park which includes Mount Victoria, and their fires and traps add to the pressure on the nuthatch. The population of the white browed nuthatch, estimated at only a few thousand, is decreasing, and no conservation measures are in place. The Algerian nuthatch is found in only four areas of Algeria, and it is possible that the total population does not exceed 1,000 birds. Fire, erosion, and grazing and disturbance by livestock have reduced the quality of the habitat, despite its location in the Taza National Park. Deforestation has also caused population declines for the vulnerable Yunnan and yellow billed nuthatches. The Yunnan nuthatch can cope with some tree loss, since it prefers open pine woodland, but although still locally common, it has disappeared from several of the areas in which it was recorded in the early 20th century. The threat to yellow billed is particularly acute on Hainan, where more than 70% of the woodland has been lost in the past 50 years due to shifting cultivation and the use of wood for fuel during Chinese government re settlement programmes. Krüper's nuthatch is threatened by urbanisation and development in and around mature coniferous forests, particularly in the Mediterranean coastal areas where the species was once numerous. A law promoting tourism came into force in Turkey in 2003, further exacerbating the threats to their habitat. The law reduced bureaucracy and made it easier for developers to build tourism facilities and summer houses in the coastal zone where woodland loss is a growing problem for the nuthatch.