Krüper's nuthatch (Sitta krueperi) is a species of bird in the family Sittidae. It is a small to medium-sized nuthatch, measuring in length. The are blue-gray, with the front half of the black in adults of both sexes, but with a less marked in the female rear. The species has a black or gray and a prominent white supercilium. The are blue-gray in males and buff-gray in females, with a large, crescent-shaped rufous pectoral patch. The Krüper's nuthatch feeds on insects in the summer and seeds, especially pines, in the fall and winter. Breeding takes place between March and May, and the nest is usually placed in a tree hole. The clutch consists of five to seven eggs, incubated by the female and fed by the male. Both parents take part in feeding the young. The Krüper's nuthatch is found in pine and other coniferous forests in Turkey, Lesvos, and the Caucasus, largely following the distribution of Turkish pine (Pinus brutia). It is found from sea level up to above sea level in places. This species is one of the small nuthatches of the "canadensis group" and is particularly very close to the Algerian nuthatch (S. ledanti), the only other species in which the black half-crown is found. The Krüper's nuthatch is threatened by habitat loss caused by forestry and especially by tourist development on the Turkish coasts. Although its numbers are declining, the species is considered to be of "least concern" by the International Union for Conservation of Nature. Taxonomy The Krüper's nuthatch was described in 1863 by the Austrian ornithologist August von Pelzeln under the protonym Sitta krüperi, from type material from İzmir. By naming the species in this way, he pays homage to its discoverer, the German ornithologist Theodor Johannes Krüper. Hans Edmund Wolters proposed the division of the genus Sitta into subgenera in 1975–1982. The Krüper's nuthatch is placed in Sitta (Mesositta) (Buturlin, 1916), which also includes the Algerian nuthatch (S. ledanti), Yunnan nuthatch (S. yunnanensis), red-breasted nuthatch (S. canadensis), Chinese nuthatch (S. villosa) and Corsican nuthatch (S. whiteheadi). The Krüper's nuthatch belongs to the species group canadensis. It is most closely related to the Algerian nuthatch. According to the International Ornithological Congress and Alan P. Peterson, no subspecies are distinguished. Phylogeny In 1998, Éric Pasquet studied the cytochrome b of the mitochondrial DNA of ten species of nuthatches, including the different species of the Sitta