The Siberian nuthatch (Sitta arctica) is a bird species of the family Sittidae. For a long time considered as a subspecies of the Eurasian nuthatch (S. europaea), it was clearly differentiated in 2006 on the basis of morphological and molecular characters. It is on average larger than the Eurasian nuthatch and also differs in some morphological features such as the shape of its bill, the size of its claws and the color of its underwing and outer rectrices. Its song has also been described as "distinctly different" from that of the Eurasian nuthatch, though without further clarification.
The Siberian nuthatch inhabits the forests northeast of Lake Baikal, up to the Bering Sea and the Sea of Okhotsk, but not near the coast. It lives in northwestern Siberia, barely exceeding the 105th meridian east in the west. It lives in larch stands and flood plains. The Siberian nuthatch has a wide range and its numbers are presumed to be stable, so the International Union for Conservation of Nature considers the bird to be of "least concern".
Taxonomy
The Siberian nuthatch was described in 1907 under its current name S. arctica, by the Russian ornithologist Sergei Buturlin, based on a specimen (holotype) from Verkhoïansk. In 1916, Buturlin proposed a division of the family Sittidae into several subfamilies, genera and subgenera. He placed Sitta arctica within a monotypic genus, Arctositta (Buturlin, 1916), judging that its morphology is sufficiently distinct from other nuthatches. In 1928, German ornithologist Otto Kleinschmidt linked the genus Arctositta to the Eurasian nuthatch group (S. europaea), and the Siberian nuthatch was subsequently considered a subspecies Sitta europaea arctica of the Eurasian nuthatch.
In 2006, ornithologists Yaroslav Red'kin and Maria Konovalova published a comprehensive review of the East Asian subspecies of the Eurasian nuthatch, proposing the subspecies S. e. arctica to be elevated to species status, in recognition of its clearly distinct morphology from the other subspecies and the fact that the Siberian nuthatch lives in partial sympatry with Sitta europaea while showing little or no hybridization. The split was accepted by the British Ornithologists' Union in 2012. These morphological analyses are consistent with mitochondrial DNA analyses also performed in 2006, which showed a large divergence (10% for the ND2 gene) between arctica and europaea. The decision was followed by the ornithologists Nigel J. Collar and John D. Pilgrim in 2007 and taken up by the International Ornithological Congress in its version 1.6 (30 June 2008). German ornithologist Hans Edmund Wolters proposed the division of the genus Sitta into subgenera in 1975–1982. The Siberian nuthatch is placed in Sitta (Sitta) (Linnaeus, 1758). According to the International Ornithological Congress and Alan P. Peterson, no subspecies are distinguished.
Phylogeny
In 2014, Eric Pasquet and colleagues published a phylogeny based on nuclear and mitochondrial DNA of 21 nuthatch species. Within the "europaea" group, the white-tailed nuthatch (S. himalayensis) – and hence the white-browed nuthatch (S. victoriae), although not included in the study – appears to be basal, and the Eurasian nuthatch is related to the chestnut-vented nuthatch (S. nagaensis) and the Kashmir nuthatch (S. cashmirensis). Indian nuthatch (S. castanea), Beautiful nuthatch (S. cinnamoventris), Burmese nuthatch (S. neglecta) and Siberian nuthatch are not included in the study. The "europaea" group is a sister group to the two rock nuthatches, the western rock nuthatch (S. neumayer) and the eastern rock nuthatch (S. tephronota), and these two clades diverged from each other thirteen million years ago. In 2020, a new phylogeny was published covering the genus more comprehensively: it includes more than four species mentioned above and uses three mitochondrial and two nuclear genes. The three species from South Asia (Indian, beautiful and Burmese nuthatches) are found to be related to the Kashmir nuthatch, but surprisingly, the Siberian nuthatch is recovered in an own branch that is quite distant from the Eurasian nuthatch of which it was long considered a subspecies.
The simplified cladogram below is based on the phylogenetic analysis of Packert and colleagues (2014):