The Yunnan nuthatch is a species of nuthatch endemic to South-Western China. It was first described by William Robert Ogilvie-Grant in 1900 based on a male holotype, and it occurs in pine forests at altitudes of up to. It is a small nuthatch, measuring 12 cm in length, without pronounced sexual dimorphism. The upperparts are gray-blue, contrasting with the light, smooth, buffy lowerparts. It has a fine white eyebrow, distinct when the plumage is fresh, and surmounting a pronounced black eye line. It is a noisy bird, producing simple, nasal sounds, sometimes in repetitive series. This blue-grey bird can be up to long, has a distinctive white eyebrow, and exhibits a small degree of sexual dimorphism. This noisy bird's diet consists of insects it finds on pine branches, and it is generally rare but can be locally common. Categorised as a near-threatened species on the IUCN Red List, it has a small range of, and a 2009 study predicted that its population could decrease by 43.6% to 47.7% by between 2040 and 2069.
Description
The upper parts of the Yunnan nuthatch are blue-grey, including the, despite being separated from the upper mantle by a paler area. It has a thin white eyebrow, which extends to the front of the bird and is above the black eye line. Each eye has a fine white circle around it, and it has a white cheek and throat. The lower parts are pale and unified, and the grey-black beak is sharp and pointed with a yellowish base. Its irises are dark brown, and the legs and feet are grey-brown. The Yunnan nuthatch is a small nuthatch, measuring around in length, and its wing chord is on male specimens and on female specimens. On males, the tale measures and on females, it measures between. Its beak measures between, the tarus is in length, and it weighs between. It exhibits little sexual dimorphism, but when the black eye trait is shown on females, their eyes are duller and greyer than those of males. The plumage is fresh in August and gradually gets worn away until the following spring. In worn plumage, the whitish feathers forming the ends of the eyebrows are worn, and the eyebrow line becomes discontinuous or inconspicuous, and the upper parts of the bird become duller. Its tail feathers and wings wear, but the blue-grey feather tips exist until at least May. The lower parts tarnish and become increasingly "dirty", and become a greyish-white colour. Sometimes, the eyebrow does not fully extend to the front. The eye line becomes narrower, and the cheek of the bird becomes grey, instead of white. The throat remains white, but the underside of the bird becomes duller, and less pale in adult specimens. Adult specimens molt from July to September, and there is sometimes a partial molt between January and February, prior to the breeding season. The giant nuthatch can occur in the same habitat as the Yunnan nuthatch, but lacks a white eyebrow. The chestnut-vented nuthatch is more similar in size to the Yunnan nuthatch than the giant nuthatch, but is different in colour and also lacks a white eyebrow.
Ecology and behaviour
Voice
The Yunnan nuthatch is a fairly noisy bird, and typically makes many individual sounds: nit, ', tit, pit, or a low and nasal '. Its cry, nit, is repeated in sets lasting four to ten seconds of five to six repetitions per second, producing a ', ', ', or a nasal ' sound. It also produces a harsh ' or ' cry, a trait shared by other small nuthatches. It sometimes produces a ' cry in calm sets of three notes per second, and can also emit nasal cries ', ', or '.
Food and breeding
The diet of the Yunnan nuthatch is not well-known, but it is known to consume insects it catches on pine branches. There is a lack of information about its reproduction, but a female was collected on 9 March that was close to laying, while recently born Yunnan nuthatches were collected on 21 May.
The Yunnan nuthatch was first described as Sitta yunnanensis by Scottish ornithologistWilliam Robert Ogilvie-Grant in 1900 based on a male holotype brought from southern Yunnan by Capt. Alfred Woodrow Stanley Wingate. It was placed into subgenus Micrositta by Buturlin in 1916, although nuthatch species are now generally grouped together under genus Sitta. According to the International Ornithological Congress and ornithologist Alan P. Peterson, there are no subspecies. In 2014, Eric Pasquet et al. published a phylogeny confirming the relationship between the Micrositta species, and found the Yunnan nuthatch to be the most basal species of the group. The canadensis group of species includes six species, which are also those of what is sometimes treated as the subgenus Sitta, the Yunnan nuthatch, the red-breasted nuthatch, the Chinese nuthatch, the Corsican nuthatch, the Krüper's nuthatch and the Algerian nuthatch. In 1953, the Dutch ornithologists Karel Voous and John G. van Marle believe that the Yunnan Nuthatch acts as a link between the canadensis and europaea groups, and at the same time that it seemed rather close to the canadensis group of which it formed a representative close to the ancestral state, than this either in terms of its distribution and its plumage. In 1957, Charles Vaurie proposed to bring the species of the Himalayan nuthatch closer. In 1998, Éric Pasquet studied the cytochrome-b of mitochondrial DNA about ten species of nuthatch, including the different species of the group of Sitta canadensis, but the Yunnan nuthatch was not included in the study. In 2014, Éric Pasquet et al. publish a nuclear and mitochondrial DNA-based phylogeny of 21 species of nuthatch and confirm the 1998 study relationships within the "canadensis group", adding the Yunnan nuthatch, which is found to be the most basic of the species this group.
In culture
The post office of the People's Republic of China represented the species in a series of stamps published between 2002 and 2006 and devoted to endemic birds of the country. Other species in the series included Cabot Tragopan, Biddulph Podoce and Taiwanese Pirolle.
Threats and protection
In 1987, Zheng Zuoxin described the Yunnan nuthatch as rare, but it is locally common in areas such as Lijiang's pine forests. It has a small range of around, and the bird disappeared from several locations in the early twentieth century. It is threatened by habitat destruction and is dependent on old pine forests, but also appears to live in degraded habitats. A 2009 study attempted to predict the impact of climate change on nuthatches in Asia, and shows the Yunnan nuthatch's distribution decreasing by between 43.6% and 47.7% by 2040–2069. The species has been classified as near-threatened species by the International Union for Conservation of Nature.
