Editing Nuthatch (section)

===Species boundaries===
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<ref name="HQlimits">Harrap & Quinn (1996) pp. 12–13 "Species limits"</ref> and comprise a [[superspecies]] along with the [[Kruper's nuthatch|Krüper's]] and [[Algerian nuthatch]]. Unusually for nuthatches, all five species excavate their own nests.<ref name="Pasquet">{{cite journal| last=Pasquet | first= Eric |date=January 1998 | title= Phylogeny of the nuthatches of the ''Sitta canadensis'' group and its evolutionary and biogeographic implications | journal= Ibis | volume= 140 | issue= 1 | pages= 150–156 | doi =10.1111/j.1474-919X.1998.tb04553.x }}</ref>

The [[Eurasian nuthatch|Eurasian]], [[chestnut-vented nuthatch|chestnut-vented]], [[Kashmir nuthatch|Kashmir]] and [[chestnut-bellied nuthatch]]es 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.<ref name="HQeurasian">Harrap & Quinn (1996) pp. 109–114 "Eurasian Nuthatch"</ref> 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.&nbsp;cinnamoventris'', which occurs in the [[Himalayas]].<ref name="Rasmussen">{{cite book| author = Rasmussen, Pamela C.|author2=Anderton, John C. |author-link2=John C. Anderton  | title = Birds of South Asia: The Ripley Guide | year = 2005 | publisher = Lynx Edicions, Barcelona. | isbn =978-84-87334-67-2 |page = 536 | author-link = Pamela C. Rasmussen|title-link=Birds of South Asia: The Ripley Guide }}</ref> Mitochondrial DNA studies have demonstrated that the white-breasted northern subspecies of Eurasian nuthatch, ''S.&nbsp;(europea) arctica'', is distinctive,<ref name="Zink">{{cite journal| last= Zink |first= Robert M. |author2= Drovetski, Sergei V.|author3=Rohwer, Sievert |date=September 2006 | title= Selective neutrality of mitochondrial ND2 sequences, phylogeography and species limits in ''Sitta europaea'' | journal=Molecular Phylogenetics and Evolution | volume=40| pmid= 16716603 | issue=3| pages= 679–686 | url =http://www.cbs.umn.edu/eeb/faculty/ZinkRobert/Selective%20neutrality.pdf | archive-url =https://web.archive.org/web/20090304212408/http://www.cbs.umn.edu/eeb/faculty/ZinkRobert/Selective%20neutrality.pdf | archive-date =2009-03-04 | doi = 10.1016/j.ympev.2005.11.002 |bibcode= 2006MolPE..40..679Z }}</ref> and also a possible candidate for full species status.<ref name="Dickinson"/> This split has been accepted by the [[British Ornithologists' Union]].<ref name= sangster2012>{{cite journal| last= Sangster | first= George |author2=Collinson, Martin |author3=Crochet, J. Pierre-André |author4=Knox, Alan G. |author5=Parkin, David T. |author6= Votier, Stephen C.  | year=2012 | title = Taxonomic recommendations for British birds: eighth report | journal= Ibis | volume=  154| issue = 4 | pages= 874–883| doi = 10.1111/j.1474-919X.2012.01273.x | doi-access= free }}</ref>

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 nuthatch|velvet-fronted]], [[yellow-billed nuthatch|yellow-billed]] and [[sulphur-billed nuthatch]]es) to a new genus, create a third genus for the [[blue nuthatch]], and possibly a fourth for the [[beautiful nuthatch]].<ref name="Dickinson">{{cite journal |last=Dickinson |first=Edward C.|author-link=Edward C. Dickinson|year=2006 |title=Systematic notes on Asian birds. 62. A preliminary review of the Sittidae |journal=[[Zoologische Verhandelingen, Leiden]] |volume=80 |pages= 225–240 |format = PDF| url = http://www.repository.naturalis.nl/document/41857}}</ref>

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''.<ref name="Manegold">{{cite journal | last= Manegold | first= Albrecht |date=April 2008 | title= Earliest fossil record of the Certhioidea (treecreepers and allies) from the early Miocene of Germany | journal= Journal of Ornithology | volume=149 | issue= 2 | pages= 223–228 | doi = 10.1007/s10336-007-0263-9| bibcode= 2008JOrni.149..223M | s2cid= 11900733 }}</ref> Two fossil species have been described in the genus ''Sitta'': ''S.&nbsp;cuvieri'' Gervais, 1852 and ''S.&nbsp;senogalliensis'' Portis, 1888, but they probably do not belong to nuthatches.<ref>
Jiří Mlíkovský, [http://www.nm.cz/download/JML-18-2002-CBE.pdf Cenozoic Birds of the World. Part 1:Europe] {{Webarchive|url=https://web.archive.org/web/20110520101755/http://www.nm.cz/download/JML-18-2002-CBE.pdf |date=2011-05-20 }} , Prague, Ninox Press, 2002, 407 p., p. 252, 273
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