Blue nuthatch

{{good article}} {{Short description|Species of small passerine bird}} {{speciesbox | name = Blue nuthatch | image = Blue Nuthatch - Cibodas Botanical Garden, Java, Indonesia.jpg | image_caption = Blue nuthatch at Cibodas Botanical Garden, Java, Indonesia | status = LC | status_system = IUCN3.1 | status_ref = <ref name="iucn status 12 November 2021">{{cite iucn |author=BirdLife International |date=2016 |title=''Sitta azurea'' |volume=2016 |article-number=e.T22711225A94284706 |doi=10.2305/IUCN.UK.2016-3.RLTS.T22711225A94284706.en |access-date=12 November 2021}}</ref> | genus = Sitta | species = azurea | authority = Lesson, 1830 | synonyms = {{*}} ''Callisitta azurea'' (Lesson, 1830) {{*}} ''Poliositta azurea'' (Lesson, 1830) {{*}} ''Dendrophila flavipes'' (Swainson, 1838) {{*}} ''Sitta flavipes'' (Swainson, 1838) | synonyms_ref = <ref>{{Cite journal|last1=Dickinson|first1=Edward C.|last2=Loskot|first2=Edward C.|last3=Loskot|first3=Vladimir M.|last4=Morioka|first4=Hiroyuki|last5=Somadikarta|first5=Soekarja|date=2000|title=Systematic notes on Asian birds. 66. Types of the Sittidae and Certhiidae|url=https://www.researchgate.net/publication/268077056|journal=Zoologische Mededelingen|issue=80|pages=287–310}}</ref> | range_map = Sitta azurea distribution.svg | range_map_caption = Blue nuthatch range }}

The '''blue nuthatch''' ('''''Sitta azurea''''') is a bird species in the nuthatch family Sittidae. It is a medium-sized nuthatch, measuring {{convert|13.5|cm|in|abbr=on}} in length. The species, which shows slight sexual dimorphism, has dramatic plumage pattern unlike any other member of its genus. Its head is black or blackish-blue dark blue {{Birdgloss|upperparts}} close to purple with azure feathers. The wings are edged with black. The throat and chest are white or a washed buff, contrasting with the upperparts and the belly of a very dark blue; the covert feathers are generally clear, blue-grey or purplish.

The blue nuthatch's ecology is poorly known, but it feeds on small invertebrates found on trees; reproduction takes place from April to June or July. It also forages in mixed-species flocks in larger groups. They can be found in the Malay Peninsula and on the islands of Sumatra and Java in Indonesia, where it inhabits subtropical or tropical moist lowland forest and subtropical or tropical moist montane forest above {{convert|900|m|ft|abbr=on}} in altitude.

Three subspecies are accepted: ''S. a. expectata'', ''S. a. nigriventer'' and ''S. a. azurea'', which differ chiefly in the colour of their {{Birdgloss|mantles}}, chests and bellies. The species' closest relatives are the velvet-fronted nuthatch (''S. frontalis''), the yellow-billed nuthatch (''S. solangiae'') and the sulphur-billed nuthatch (''S. oenochlamys''). The population of the species has not been determined but the species appears to be at low risk of extinction because of the extent of its distribution. It has been classified as of least concern by the International Union for Conservation of Nature.

== Taxonomy == The blue nuthatch was first described in 1830 under its current binomial name, ''Sitta azurea'', by the French naturalist René Primevère Lesson (1794–1849).<ref name="Lesson1830">{{cite book| language=French|last= Lesson |first= René Primevère|title=Traité d'ornithologie, ou, Tableau méthodique des ordres, sous-ordres, familles, tribus, genres, sous-genres et races d'oiseaux |publisher=F. G. Levrault|page=316 |url= https://www.biodiversitylibrary.org/item/111050#page/354/mode/1up |oclc=768399957|year=1831|volume= 1 }}</ref><ref>{{cite book|last=Fischer|first=Dan L.|title=Early Southwest Ornithologists, 1528–1900|page=18|chapter=French Traders, 1827–1828| chapter-url= https://books.google.com/books?id=vPOxIR5OuIYC&pg=PA18 |publisher= University of Arizona Press|year=2001|isbn=0-8165-2149-2}}</ref> ''Sitta'' is derived from the Ancient Greek name for nuthatches, {{lang|grc|σίττη}}, ''sittē''.<ref name="Jobling">{{cite book|last=Jobling|first=James A.|year=2010|title=The Helm Dictionary of Scientific Bird Names|url=https://archive.org/details/Helm_Dictionary_of_Scientific_Bird_Names_by_James_A._Jobling|publisher=Christopher Helm|isbn=978-1-4081-2501-4|page=[https://archive.org/details/Helm_Dictionary_of_Scientific_Bird_Names_by_James_A._Jobling/page/n357 357]}}</ref>{{sfn|Matthysen|2010|page=4}} The genus has occasionally been divided into seven subgenera,{{Cref2|fn. 1}} of which the blue nuthatch is placed alone in ''Poecilositta'' (Buturlin 1916).{{sfn|Matthysen|2010|page=269–270}}

The name "nuthatch", first recorded in 1350, is derived from "nut" and a word probably related to "hack", since these birds hack at nuts they have wedged into crevices.<ref name="oedjar">{{cite web|title= Entry for 'Nuthatch' |work=Oxford English Dictionary|url= http://www.oed.com/view/Entry/129307?rskey=aKsRBB&result=1&isAdvanced=false#eid|publisher=Oxford University Press|access-date=17 April 2014|url-access=subscription }}</ref>

The nuthatches constitute a genus, ''Sitta'', of small passerine birds in the family Sittidae,<ref>{{cite book|last1=Sibley|first1=David|last2=Elphick|first2=Chris|last3=Dunning|first3=John Barnard|title=Sibley guide to bird life and behavior|isbn=978-0-679-45123-5|publisher=Alfred A. Knopf|year=2001|page=[https://archive.org/details/sibleyguidetobir00sibl_1/page/434 434]|url-access=registration|url=https://archive.org/details/sibleyguidetobir00sibl_1/page/434}}</ref> typified by short, compressed wings and short, square tails with 12 feathers, a compact body, longish pointed {{Birdgloss|bills}}, strong toes with long claws, and behaviourally, by their unique head-first manner of descending tree trunks. Most nuthatches have blue-grey upperparts and a black eyestripe.<ref name="Pasquet2014">{{cite journal|last1=Pasquet|first1=Eric |last2=Barker|first2=F. Keith|last3=Martens| first3=Jochen|last4=Tillier|first4=Annie|last5=Cruaud| first5=Corinne|last6=Cibois|first6=Alice| title=Evolution within the nuthatches (Sittidae: Aves, Passeriformes): molecular phylogeny, biogeography, and ecological perspectives|journal=Journal of Ornithology|date=April 2014|volume=155 |issue=3 |pages=755–765 |doi=10.1007/s10336-014-1063-7|bibcode=2014JOrni.155..755P |s2cid=17637707 }}</ref> In 2006, the ornithologist Edward C. Dickinson proposed splitting ''Sitta'' in multiple genera on the basis of distinct morphological traits. He suggested as candidates the velvet-fronted nuthatch (''Sitta frontalis'') and the blue nuthatch, the morphology of which he describes as "rather aberrant ... in spite of a character trait (white edges to wing feathers) shared with ''Sitta formosa''", and that doing so might, in turn, require the beautiful nuthatch (''S. formosa'') to be split off as well. He stated, however, that a molecular study would be warranted prior to any re-classification.<ref name="Dickinson2006">{{cite journal|last=Dickinson|first=Edward C.|year=2006|title=Systematic notes on Asian birds. 62. A preliminary review of the Sittidae|journal=Zoologische Verhandelingen, Leiden|publisher=Rijksmuseum|volume=80| issue=5|pages=225–240 |url=http://www.repository.naturalis.nl/document/41857|issn=0024-0672}}</ref><ref name="HBW">{{cite book|first1=Josep del|last1=Hoyo|first2=Andrew|last2=Elliott|first3=David A.|last3=Christie|year=2008|volume=13|title=Handbook of the Birds of the World: Penduline-tits to Shrikes|url=http://www.hbw.com/family/nuthatches-sittidae|publisher=Lynx Edicions (HBW Alive for online version)|chapter=Sittidae (Nuthatches): Systematics|doi=10.2173/bow.sittid1.01 }}</ref>

In 2014, Eric Pasquet and colleagues published a phylogeny based on examination of nuclear and mitochondrial DNA of 21 nuthatch species.{{Cref2|fn. 2}} The position of the blue nuthatch within the genus was not established with certainty, having a far lower correlation than many others in the model. Nevertheless, under the findings the species appears best represented by a clade comprising the velvet-fronted nuthatch and the sulphur-billed nuthatch ''S. oenochlamys'' (and presumably also the very similar yellow-billed nuthatch ''S. solangiae'', which remains untested<ref name="Päckert"/>). These tropical Asian nuthatches are themselves a sister clade to one comprising the subgenus ''Sitta'' (''Micrositta'') (sometimes called the ''S. canadensis'' group), along with the brown-headed nuthatch (''S. pusilla'') and the pygmy nuthatch (''S. pygmaea'').<ref name="Pasquet2014" /><ref>{{Cite journal|last=Harrap|first=Simon|title=Blue Nuthatch (Sitta azurea)|date=2020-03-04|url=https://birdsoftheworld.org/bow/species/blunut1/1.0/introduction|journal=Birds of the World|editor-last=Billerman|editor-first=Shawn M.|publisher=Cornell Lab of Ornithology|language=en|doi=10.2173/bow.blunut1.01|s2cid=216391261 |access-date=2021-12-22|editor2-last=Keeney|editor2-first=Brooke K.|editor3-last=Rodewald|editor3-first=Paul G.|editor4-last=Schulenberg|editor4-first=Thomas S.|url-access=subscription}}</ref> These results were confirmed by a further study in 2020 by Martin Päckert and colleagues.<ref name="Päckert">{{cite journal | last1=Päckert | first1=Martin | last2=Bader-Blukott | first2=Marcella | last3=Künzelmann | first3=Berit | last4=Sun | first4=Yue-Hua | last5=Hsu | first5=Yu-Cheng | last6=Kehlmaier | first6=Christian | last7=Albrecht | first7=Frederik | last8=Illera | first8=Juan Carlos | last9=Martens | first9=Jochen | title=A revised phylogeny of nuthatches (Aves, Passeriformes, Sitta) reveals insight in intra- and interspecific diversification patterns in the Palearctic |journal=Vertebrate Zoology |volume=70 | pages=241–262 | date=2020 | doi=10.26049/VZ70-2-2020-10 | doi-access=free | url=https://zenodo.org/record/7024248 | access-date=2025-05-21}}</ref>

{{quote box | title = Phylogenetic tree detail Nuthatch phylogenic detail according to Pasquet, et al. (2014):<ref name="Pasquet2014"/> | quote = {{Tree list}} * Weakly-supported clade ** {{Tree list/branching}} *** {{Tree list/branching}} **** Brown-headed nuthatch (''S. pusilla'') **** {{Tree list/final branch}} Pygmy nuthatch (''S. pygmaea'') *** {{Tree list/final branch }} ''Sitta canadensis'' group ** {{Tree list/final branching}} *** '''Blue nuthatch''' (''S. azurea'') *** {{Tree list/final branching}} **** Velvet-fronted nuthatch (''S. frontalis'') **** {{Tree list/final branch}} Sulphur-billed nuthatch (''S. oenochlamys'') {{Tree list/end}} | align = center | width = auto | style = font-size:110%; border-bottom:1px #aaa solid; }}

=== Subspecies === Three subspecies of blue nuthatch are accepted:<ref name="IOC">{{cite web | title=Nuthatches, Wallcreeper, treecreepers, spotted creepers, mockingbirds, starlings, oxpeckers – IOC World Bird List | website=IOC World Bird List – Version 14.2 | date=2025-02-20 | url=https://www.worldbirdnames.org/new/bow/nuthatch/ | access-date=2025-05-21}}</ref>{{sfn|Harrap|1996|page=169}}

* ''S. a. expectata'' (Hartert, 1914), described in 1914 by German ornithologist Ernst Hartert as ''Callisitta azurea expectata'' from a holotype from the Semangko Pass in Pahang on the Malay Peninsula;<ref name="Callisitta azurea">{{cite journal|journal= Bulletin of the British Ornithologists' Club|last= Hartert|first= Ernst|volume= 35|year=1914|page=34|title=Callisitta azurea expectata|url=https://archive.org/stream/bulletinofb3537191417brit#page/n63/mode/2up|oclc=761190665|publisher=British Ornithologists' Club}}</ref> it is also found in Sumatra;<ref name="IOC" /> * ''S. a. nigriventer'' (Robinson & Kloss, 1919), described in 1919 by British zoologists Herbert Robinson and Cecil Kloss as ''Poliositta azurea nigriventer'' from a holotype from Mount Gede<ref name="RobinsonKloss1919">{{cite journal|first1=Herbert Christopher|last1=Robinson|first2=Cecil Boden|last2=Kloss|year=1919|title=New subspecies of Malay birds: Poliositta azurea nigiventer|journal=Bulletin of the British Ornithologists' Club|publisher=British Ornithologists' Club|volume= XL|page=17|url=https://www.biodiversitylibrary.org/item/100942#page/284/mode/2up}}</ref> in West Java, Indonesia.<ref name="IOC" /> The British ornithologist William Swainson had earlier described it under the name ''Dendrophila flavipes'' in 1838, but this name was little used subsequently, and can be considered a ''nomen oblitum'' ("forgotten name");<ref name="Dickinsonetal2006">{{cite journal |first1=E. C. |last1=Dickinson |first2=V. M. |last2=Loskot |first3=H. |last3=Morioka |first4=S. |last4=Somadikarta |first5=R. |last5=van den Elzen |title=Systematic notes on Asian birds. 66. Types of the Sittidae and Certhiidae |journal=Zoologische Verhandelingen, Leiden |volume=80 |issue=18 |date=December 2006 |pages=287–310 |url=http://www.zoologischemededelingen.nl/cgi/t/text/get-pdf?c=zoomed;idno=8005a20 |oclc=700480502 |access-date=2014-05-14 |archive-url=https://web.archive.org/web/20160304060230/http://www.zoologischemededelingen.nl/cgi/t/text/get-pdf?c=zoomed;idno=8005a20 |archive-date=2016-03-04 }}</ref> * ''S. a. azurea'' (Lesson, 1830) the nominate subspecies, was described in 1830 by René Lesson<ref name="Lesson1830" /> from a specimen possibly from the Arjuno-Welirang stratovolcano; inhabits central and eastern Java.<ref name="IOC" />

== Description == The blue nuthatch is a medium-sized nuthatch that has an average length of {{convert|13.5|cm|in|abbr=on}}. The weight is not known.{{sfn|Harrap|1996|page=169}} Its appearance differs significantly from all other nuthatches. All of its subspecies are broadly black and white{{sfn|Harrap|1996|pages=48–49}} (especially when viewed in low-light conditions in which their dark blue colour is not apparent) and have upper plumage shot through with dramatic notes of cobalt, azure and other lighter shades of blue, as well as greys and purples. The head is black, or blackish-blue with a broad, pale blue {{Birdgloss|eye ring}}.<ref name="NatGeo">{{cite book|title=National Geographic Complete Birds of the World|chapter-url=https://books.google.com/books?id=0TIiIdLp9xkC&pg=PA307|page=307|chapter=Nuthatches and Wallcreeper|year = 2009|publisher=National Geographic|editor=Harris, Tim|isbn=978-1-4262-0403-6}}</ref>{{sfn|Harrap|1996|pages=168–169}}

The three subspecies vary in the colour of their mantle, chest and belly. The upperparts are dark blue at the mantle or purplish in some subspecies. The rectrices are pale blue in the middle with a black border and contrast sharply with the dark areas of the coat. The throat and breast are white, or washed buff, especially in ''S. a. nigriventer''. The belly and abdomen are blackish, contrasting with blue-grey or purplish {{Birdgloss|coverts}}. The bill is lavender, slightly tinged with green, and black at the tip; the legs are a pale blue-grey and the claws are slate-grey or black.<ref name="NatGeo" />{{sfn|Harrap|1996|pages=168–169}}

The species displays no significant sexual dimorphism, but the Japanese ornithologist Nagamichi Kuroda describes the female as having slightly duller upperparts. Juveniles resemble adults, but have a duller crown and ear coverts, as well as a brown cast that does not cover their entire body. The belly is a dull black and the undertail coverts are variably edged creamy white. The juvenile's bill is blackish, with a pink base. Adults experience a partial moult before the breeding season (February–March for ''S. a. expectata''; March–April for ''S. a. azurea'') involving the throat, chest and mantle; a complete moult takes place after the breeding season (March–April and August in Java in Malaysia).{{sfn|Harrap|1996|pages=168–169}}

<gallery class="center" caption="The three subspecies and their distinct morphological characteristics" widths="200px" heights="130px"> File:Sitta azurea expectata png.png|''Sitta azurea expectata'' - Malay Peninsula, Sumatra Dark blue upper parts and azure coverts. File:Sitta azurea nigriventer png.png|''Sitta azurea nigriventer'' - Western Java Purplish-blue upper parts, blue coverts and buffy belly. File:Sitta azurea azurea png.png|''Sitta azurea azurea'' - Central and eastern Java Purple upper parts and violet coverts. </gallery>

=== Songs and calls === {{Birdsong|species=''Sitta azurea''|url=http://www.xeno-canto.org/species/Sitta-azurea}} The species' calls include a melodious ''tup'' or ''tip'', a sudden ''whit'', a thin hissing ''sit'', and a fuller, harder, and more forceful ''chit''. When excited, ''sit'' and ''chit'' notes are frequently given quickly and repetitively as a ''chi-chit, chit-chit-chit'' or ''chir-ri-rit'', which can be prolonged, accelerated into staccato trilling ''tititititititik'', or even becoming a rattling ''tr-r-r-r-r-r-t''. Other calls include a thin, squeaking ''zhe'' and ''zhe-zhe'', a squeaky toy-like nasal ''snieu'' or ''kneu'', and a buzzy ''chirr-u''. The vocal repertoire of the blue nuthatch is quite varied and is reminiscent of the velvet-fronted nuthatch and, to a lesser extent, the sulphur-billed nuthatch.<ref name="HBW" />

== Behaviour and ecology == [[File:Blue Nuthatch.ogv|thumb|right|A blue nuthatch of subspecies ''S. a. expectata'' foraging in a tree, Fraser's Hill, Malaysia]] The blue nuthatch is very active, often seen running on tree branches in pairs,<ref name="Wells2007">{{cite book|first=David R. |last=Wells |title=The Birds of the Thai-Malay Peninsula|volume=2|chapter=Passerines |editor=Christopher Helm|year=2007 |pages=431–432|publisher=Christopher Helm |isbn=978-0-7136-6534-5}}</ref> in larger groups, or mingling in mixed-species foraging flocks.{{sfn|Harrap|1996|page=168}}

=== Diet === The blue nuthatch feeds on arthropods, of which some have been particularly identified as common in its diet, including ''Trachypholis'' beetles, click beetles, Eumolpinae leaf beetles, spiders, and moth caterpillars.<ref name="Becking1989">{{cite book |last=Becking |first=J. H. |title=Henri Jacob Victor Sody (1892-1959): His Life and Work: a Biographical and Bibliographical Study |chapter=Diets of Javanese birds |editor=Brill Archive |year=1989|page=209}}</ref> It typically forages for prey in the upper half of large trees, and occasionally in smaller trees.{{sfn|Harrap|1996|page=168}} While prospecting on tree trunks, the bird protects its corneas from falling bark and other debris by contracting the bare skin around its eyes, an adaptation apparently unique to the species.<ref name="Curio2001">{{cite journal|language=de |first=Eberhard |last=Curio |title=Wie Vögel ihr Auge schützen: Zur Arbeitsteilung von Oberlid, Unterlid und Nickhaut |journal=Journal für Ornithologie |volume=142 |year=2001|issue=3 |pages=257–272 |doi= 10.1007/BF01651365|bibcode=2001JOrn..142..257C |s2cid=38854629 }}</ref>

=== Breeding === Its breeding has not been extensively studied. The nest is made in a small tree hole in which it lays three to four dirty-white eggs, washed in greyish-lavender tones and densely speckled with reddish-brown; the eggs measure {{convert|19.3|x|13.4|mm|in|abbr=on}}. In Peninsular Malaysia, juveniles just reaching maturity were observed in late June; on the island of Java, the breeding season takes place from April to July; and on Sumatra an adult feeding its young was observed on 9 May.{{sfn|Harrap|1996|page=168}}

=== Predation === Little has been specifically reported on blue nuthatch predators, but one individual was seen to freeze during the passage of a prospecting black eagle (''Ictinaetus malayensis'').<ref name="Wells2007" />

== Distribution and habitat == [[File:Blue Nuthatch - Fraser's Hills - Malaysia MG 6508 (19419345920).jpg|thumb|upright|A blue nuthatch on a tree trunk at Fraser's Hill, Malaysia.]] This species lives in the Malay Peninsula (in extreme southern Thailand and northern Malaysia) and in Indonesia on the islands of Sumatra and Java.<ref name="iucn status 12 November 2021" /><ref name="IOC" /> In Malaysia, the species has been observed in Bukit Larut, in the state of Perak, in the Titiwangsa Mountains, in southern Hulu Langat, in the state of Selangor, as well as some isolated populations on the slopes of the massive Mount Benom in the state of Pahang, on Mount Tahan located at the Pahang-Kelantan border, on Mount Rabong in Kelantan and at Mount Padang in the Sultanate of Terengganu.{{sfn|Harrap|1996|page=168}}

In Sumatra, the bird is found throughout the Barisan Mountains, and has been observed in the Gayo Highlands of Aceh province, the Batak Highlands of northern Sumatra, and at Dempo in the south of the island.{{sfn|Harrap|1996|page=168}} In a 1918 expedition by Robinson and Kloss, they commented: "from the commencement of heavy jungle on the valley slopes up to about 8,000 feet on Korinchi Peak this strikingly coloured little Nuthatch was very common, feeding on tall tree trunks in parties of six or seven."<ref name="RobinsonKloss1918">{{cite journal|first1=Herbert Christopher |last1=Robinson |first2=Cecil Boden |last2=Kloss |year=1918 |title=Results of an expedition to Korinchi Peak, 12,400 ft., Sumatra. – Pt. II: Birds |journal=Journal of the Federated Malay States Museums|publisher=Kelly & Walsh |volume= VIII|oclc=15726954|url=https://archive.org/stream/journaloffed411191124sela#page/n559/mode/2up|page=229}}</ref>

The blue nuthatch is typically found on mountains, inhabiting subtropical or tropical moist lowland forest and subtropical or tropical moist montane forest. In Malaysia, it is found from {{convert|1,070|m|ft|abbr=on}} to the highest point in the country at {{convert|2,186|m|ft|abbr=on}}. In Sumatra, the species has been reported at an altitudinal range of between {{convert|900|m|ft|abbr=on}} and {{convert|2,400|m|ft|abbr=on}},{{sfn|Harrap|1996|page=168}} and on Java, between {{convert|915|m|ft|abbr=on}} and {{convert|2,745|m|ft|abbr=on}}.{{sfn|Harrap|1996|page=168}} It has also been seen occasionally at lower altitudes on the plains of Java.{{sfn|Harrap|1996|page=168}}<ref name="MacKinnon">{{cite book | last=MacKinnon | first=John Ramsay | title=Field Guide to the Birds of Java and Bali | publisher=Gajah Mada University Press | publication-place=Yogyakarta | date=1988 | isbn=979-420-092-1 | pages=257–258}}</ref>

== Threats and protection== The blue nuthatch is a common bird in Sumatra, including in the area of Kerinci Seblat National Park<ref name="RobinsonKloss1918"/> and relatively common in Malaysia and Java.{{sfn|Harrap|1996|page=168}} It has a very wide distribution area, approaching {{convert|361,000|km2|abbr=on}}.<ref name="BLI">{{cite web|last1=Ekstrom|first1=Jonathan|last2=Butchart|first2=Stuart|title= Blue Nuthatch - BirdLife Species Factsheet |publisher=BirdLife International|url= http://www.birdlife.org/datazone/speciesfactsheet.php?id=6901 |access-date=12 May 2014}}</ref> The population has not been rigorously estimated but is considered significant and at low risk, despite BirdLife International's observation that some decline is likely (but not as yet confirmed) due to known destruction and fragmentation of areas the species is known to inhabit.<ref name="BLI" /> The blue nuthatch is placed in the category of least concern by the International Union for Conservation of Nature.<ref name="iucn status 12 November 2021" />

== Footnotes == {{Cnote2 Begin|liststyle=upper-alpha|colwidth=40em}} {{Cnote2|fn. 1|Being ''Callisitta'', ''Poecilositta'', ''Oenositta'', ''Sitta'', ''Mesositta'', ''Micrositta'' and ''Leptositta''.{{sfn|Matthysen|2010|page=269–270}} }} {{Cnote2|fn. 2|The 21 species are out of 24 accepted as making up the genus by Harrap and Quinn as of 1996. Of these, the study omitted the Indian nuthatch (''Sitta castanea''), the yellow-billed nuthatch (''Sitta solangiae'') and the white-browed nuthatch (''Sitta victoriae''). The International Ornithological Congress now accepts 29 species as of 2025, based on the elevation of five taxa from subspecies to full species status, including Przevalski's nuthatch (''S. przewalskii''), Bahama nuthatch (''S. insularis''), and three species from the ''S. europaea'' group.<ref name="Pasquet2014" />}} {{Cnote2 End}}

== Citations == {{Reflist|30em}}

== Bibliography == {{Refbegin}} * {{cite book|last=Harrap|first=Simon|publisher=Christopher Helm|others=Illustrated by David Quinn|title= Tits, Nuthatches and Treecreepers|year=1996|editor=Christopher Helm|language=en|isbn=0-7136-3964-4}} * {{cite book|last=Matthysen|first=Erik|others=Illustrated by David Quinn|title=The Nuthatches|publisher=A & C Black|year=2010|isbn=978-1-4081-2870-1|language=en}} {{Refend}}

blue nuthatch Category:Birds of the Malay Peninsula Category:Birds of Sumatra Category:Birds of Java blue nuthatch Category:Taxa named by René Lesson Category:Articles containing video clips Category:Taxonomy articles created by Polbot