Editing Changeable hawk-eagle (section)

==Taxonomy==
The changeable hawk-eagle was [[Species description|formally described]] in 1788 by the German naturalist [[Johann Friedrich Gmelin]] in his revised and expanded edition of [[Carl Linnaeus]]'s ''[[Systema Naturae]]''. He placed it with the eagles, hawks and relatives in the [[genus]] ''[[Falco (bird)|Falco]]'' and coined the [[binomial nomenclature|binomial name]] ''Falco cirrhatus''.<ref>{{Cite book |last=Gmelin |first=Johann Friedrich |url=https://www.biodiversitylibrary.org/page/2896874 |title=Systema naturae per regna tria naturae : secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis |publisher=Georg. Emanuel. Beer |year=1788 |edition=13th |volume=1, Part 1 |location=Lipsiae [Leipzig] |page=274 |language=Latin |author-link=Johann Friedrich Gmelin}}</ref> Gmelin's description was based on the "crested Indian falcon" or the ''Falco Indicus cirratus'' that had been first described in 1676 by the English naturalists [[Francis Willughby]] and [[John Ray]] from a live bird kept in the Royal Aviary in [[St James's Park]], London.<ref>{{Cite book |last=Willughby |first=Francis |url=https://www.biodiversitylibrary.org/page/56923384 |title=Ornithologiae libri tres |publisher=John Martyn |year=1676 |location=London |page=48 |language=Latin |author-link=Francis Willughby}}</ref><ref>{{Cite book |last=Willughby |first=Francis |url=https://www.biodiversitylibrary.org/page/41441879 |title=The Ornithology of Francis Willughby of Middleton in the County of Warwick |publisher=John Martyn |year=1678 |editor-last=Ray |editor-first=John |editor-link=John Ray |location=London |page=82, No. 12 |author-link=Francis Willughby}}</ref><ref>{{Cite book |last=Ray |first=John |url=https://www.biodiversitylibrary.org/page/6355280 |title=Synopsis methodica avium & piscium |publisher=William Innys |year=1713 |volume=Avium |location=London |page=14, No. 12 |language=Latin |author-link=John Ray}}</ref> The changeable hawk-eagle was formerly placed in the genus ''[[Spizaetus]]'' but it and nine other Old World hawk-eagles were moved to the resurrected genus ''[[Nisaetus]]'' following the publication in 2005 and 2007 of two [[molecular phylogentic]] studies.<ref>{{Cite journal |last1=Helbig |first1=A.J. |last2=Kocum |first2=A. |last3=Seibold |first3=I. |last4=Braun |first4=M.J. |date=2005 |title=A multi-gene phylogeny of aquiline eagles (Aves: Accipitriformes) reveals extensive paraphyly at the genus level |journal=Molecular Phylogenetics and Evolution |volume=35 |issue=1 |pages=147–164 |doi=10.1016/j.ympev.2004.10.003|pmid=15737588 |bibcode=2005MolPE..35..147H }}</ref><ref>{{Cite journal |last1=Haring |first1=E. |last2=Kvaløy |first2=K. |last3=Gjershaug |first3=J.-O. |last4=Røv |first4=N. |last5=Gamauf |first5=A. |date=2007 |title=Convergent evolution and paraphyly of the hawk-eagles of the genus ''Spizaetus'' (Aves, Accipitridae) – phylogenetic analyses based on mitochondrial markers |journal=Journal of Zoological Systematics and Evolutionary Research |volume=45 |issue=4 |pages=353–365 |doi=10.1111/j.1439-0469.2007.00410.x}}</ref><ref name="ioc">{{Cite web |date=August 2022 |editor-last=Gill |editor-first=Frank |editor-link=Frank Gill (ornithologist) |editor2-last=Donsker |editor2-first=David |editor3-last=Rasmussen |editor3-first=Pamela |editor3-link=Pamela Rasmussen |title=Hoatzin, New World vultures, Secretarybird, raptors |url=https://www.worldbirdnames.org/bow/raptors/ |access-date=5 December 2022 |website=IOC World Bird List Version 12.2 |publisher=International Ornithologists' Union}}</ref> The genus ''Nisaetus'' had been introduced in 1836 by the English naturalist [[Brian Houghton Hodgson]].<ref>{{Cite journal |last=Hodgson |first=Brian Houghton |author-link=Brian Houghton Hodgson |date=1836 |title=Summary description of some new species of Falconidae |url=https://www.biodiversitylibrary.org/page/37188325 |journal=Journal of the Asiatic Society of Bengal |volume=5 |issue=52 |pages=227–231 [228–230]}}</ref> The genus name ''Nisaetus'' combines the [[Medieval Latin]] ''nisus'' for a sparrowhawk with the [[Ancient Greek]] ''aetos'' meaning "eagle". The specific epithet ''cirrhatus'' is from [[Latin]] ''cirratus'' meaning "curly-headed".<ref>{{Cite book |last=Jobling |first=James A. |title=The Helm Dictionary of Scientific Bird Names |publisher=Christopher Helm |year=2010 |isbn=978-1-4081-2501-4 |location=London |page=[https://archive.org/stream/Helm_Dictionary_of_Scientific_Bird_Names_by_James_A._Jobling#page/n272/mode/1up 272], [https://archive.org/stream/Helm_Dictionary_of_Scientific_Bird_Names_by_James_A._Jobling#page/n110/mode/1up 110]}}</ref>

The taxonomy of the wide-ranging changeable hawk-eagle is complex and confusing, with few authorities agreeing on whether the species in fact houses a [[species complex]].<ref name="Gamauf">{{Cite journal |last1=Gamauf |first1=Anita |last2=Gjershaug |first2=Jan-Ove |last3=Røv |first3=Nils |last4=Kvaløy |first4=Kirsti |last5=Haring |first5=Elisabeth |year=2005 |title=Species or subspecies? The dilemma of taxonomic ranking of some South-East Asian hawk-eagles (genus ''Spizaetus'') |journal=Bird Conservation International |volume=15 |issue=1 |pages=99–117 |doi=10.1017/S0959270905000080 |doi-access=free}}</ref> Gamauf ''et al.'' (2005) analyzed [[mtDNA]] [[cytochrome b|cytochrome ''b'']] and [[mtDNA control region|control region]] [[DNA sequence|sequence]] data of a considerable number of specimens of the crested hawk-eagle and some relatives. Despite the large sample, even the most conspicuous [[dichotomy]] - that between the crested and crestless groups - was not as well resolved as it might have been expected to be.<ref name= Gamauf/> At least one widely accepted genetic study has resulted in a recent revision to the recognition of a new species, as the [[Flores hawk-eagle]] has traditionally been treated as a subspecies of the changeable hawk-eagle, but it is now often treated as a separate species, ''N. floris''.<ref name="split">Gjershaug, J. O., Kvaløy, K., Røv, N., Prawiradilaga, D. M., Suparman, U., and Rahman, Z. (2004). ''[http://www.orientalbirdclub.org/publications/forktail/20pdfs/Gjershaug-Flores.pdf The taxonomic status of Flores Hawk-Eagle Spizaetus floris.] {{webarchive |url=https://web.archive.org/web/20110610201753/http://www.orientalbirdclub.org/publications/forktail/20pdfs/Gjershaug-Flores.pdf |date=June 10, 2011 }}'' Forktail 20: 55–62</ref> The Flores and changeable hawk-eagles are regarded as sister species.<ref name="Lerner">{{Cite journal |last1=Lerner |first1=Heather |last2=Christidis |first2=Les |last3=Gamauf |first3=Anita |last4=Griffiths |first4=Carole |last5=Haring |first5=Elisabeth |last6=Huddleston |first6=Christopher J. |last7=Kabra |first7=Sonia |last8=Kocum |first8=Annett |last9=Krosby |first9=Meade |last10=KvaløY |first10=Kirsti |last11=Mindell |first11=David |last12=Rasmussen |first12=Pamela |last13=RøV |first13=Nils |last14=Wadleigh |first14=Rachel |last15=Wink |first15=Michael |date=2017-01-09 |title=Phylogeny and new taxonomy of the Booted Eagles (Accipitriformes: Aquilinae) |url=https://www.mapress.com/zt/article/view/zootaxa.4216.4.1 |journal=Zootaxa |volume=4216 |issue=4 |pages=zootaxa.4216.4.1 |doi=10.11646/zootaxa.4216.4.1 |pmid=28183111 |issn=1175-5334|hdl=11250/2443953 |hdl-access=free }}</ref>  The three small-island [[taxa]] (''N. c. andamanensis'', ''N. c. vanheurni'', and ''[[Flores hawk-eagle|N. floris]]'') as a whole each appear as [[monophyletic]] lineages. Their placement is even more unresolved, with ''N. floris'' being apparently a very ancient lineage. The other two seem quite certainly to derive from ''N. c. limnaeetus''. The latter taxon has a confusing [[phylogeny]]. Different lineages exist that are apparently not stable in space and time, are best described as [[polytomy]], from which the similar island taxa derive.<ref name= Gamauf/><ref name= Lerner/> Obviously, ''N. c. limnaeetus'' does not represent a [[monophyletic]] lineage. Neither the biological nor the phylogenetic [[species concept]]s, nor [[phylogenetic systematics]] can be applied to satisfaction. The crested group apparently is close to becoming a distinct species. The island taxa derived from ''N. c. limnaeetus'' appear to have undergone [[founder effect]]s, which has restricted their genetic diversity. In the continental population, genetic diversity is considerable, and the evolutionary pattern of the two studied genes did not agree, and neither did the origin of specimens show clear structures. ''N. c. limnaeetus'' thus is best considered a [[metapopulation]].<ref name= Gamauf/>

Gamauf ''et al.'' (2005) therefore suggest the island taxa which are obviously at higher risk of [[extinct]]ion are, for [[conservation biology|conservation]] considered [[evolutionary significant unit]]s regardless of their [[systematics|systematic]] status. This case also demonstrates that a too-rigid interpretation of [[cladistics]] and the desire for monophyletic taxa, as well as universal application of single-species concept to all birds will undermine correct understanding of [[evolution]]ary relationships. It would even not be inconceivable to find mainland lineages to group closely with the western island taxa, if little [[genetic drift]] had occurred in the initial population. nonetheless, the divergence of this species' lineages seems to have taken place too recently to award them species status, as compared to the level of genetic divergence at which [[clade]]s are usually considered distinct species.<ref name= Gamauf/> ''N. c. limnaeetus'' appears for all that can be said with reasonable certainty [[Basal (phylogenetics)|basal]] pool of lineages in the crestless group that, despite not being monophyletic, should be considered a valid taxon as long as [[gene flow]] is possible through its range. In addition, as [[ancient DNA]] from museum specimens was used extensively, the possibility of [[ghost lineage]]s must be considered. If it is assumed that all or most of the ancient lineages still exist today, considerable [[genetic recombination|recombination]] must have taken place as the two genes' phylogenies do not agree much, indicating a healthy level of gene flow. Whether this still holds true today remains to be determined.<ref name= Gamauf/>

Two distinct groups exist in the changeable hawk-eagle; one with crests and one without or with hardly visible crests. A 2020 study found that the reproductive isolation between the two groups was weak and recommended treating the two groups as [[conspecific]].<ref>{{Cite journal |last1=Gjershaug |first1=J.O. |last2=Diserud |first2=O.H. |last3=Kleven |first3=O. |last4=Rasmussen |first4=P.C. |last5=Espmark |first5=Y. |date=2020 |title=Integrative taxonomy of the Changeable Hawk-Eagle ''Nisaetus cirrhatus'' complex (Accipitriformes: Accipitridae) in India |journal=Zootaxa |volume=4789 |issue=2 |pages=554–574 |doi=10.11646/zootaxa.4789.2.10 |pmid=33056440 |hdl-access=free |hdl=11250/2675535}}</ref> Dark [[morph (zoology)|morphs]] exist for some populations.<ref name="Amadon">{{Cite journal |last=Amadon |first=Dean |date=1953 |title=Remarks on the Asiatic Hawk-Eagles of the Genus ''Spizaëtus'' |journal=Ibis |volume=95 |issue=3 |pages=492–500 |doi=10.1111/j.1474-919X.1953.tb00709.x}}</ref>

===Subspecies===
[[File:Nisaetus cirrhatus wing patterns.jpg|thumb|In flight, changeable hawk-eagles have distinctly short but broad wings with dark barring on flight feathers and a long tail.]]
'''Changeable hawk-eagle group'''
* ''N. c. cirrhatus'' ([[Johann Friedrich Gmelin|Gmelin, JF]], 1788) : The nominate subspecies is found in the [[Indian subcontinent|peninsular India]], from the [[Gangetic plain]] southwards throughout the remainder of the country.  It is monomorphic in colour with no dark morph. The nominate subspecies is relatively pale above compared to other races, with a slightly more rufous hue to the head. It tends to be less extensively streaked below down to the lower breast below compared to other races, with dark wing lings and a strongly barred tail. In the juvenile plumage, the nominate race has a strongly buffy headed and has underparts that are flecked and spotted. The crest tends to be longest in this race, with common measurements of {{convert|10|to|14|cm|in|abbr=on}} in length, therefore the race is commonly referred to as the crested hawk-eagle.<ref name= Ferguson-Lees/><ref name= Gamauf/> It is one of the two larger subspecies. [[Wing chord (biology)|Wing chord]] length ranges from {{convert|405|to|442|mm|in|abbr=on}} in males and from {{convert|448|to|462|mm|in|abbr=on}} in females. In both sexes, the tail commonly measures {{convert|280|to|300|mm|in|abbr=on}} and [[Tarsus (skeleton)|tarsus]] from {{convert|102|to|110|mm|in|abbr=on}}.<ref name= Ferguson-Lees/>
* ''N. c. ceylanensis'' (Gmelin, JF, 1788): This race is endemic to [[Sri Lanka]] but some authorities also include [[Travancore]] in the southern tip of India as part of this race's range.<ref name= Ferguson-Lees/><ref name= Amadon/> This race has a proportionally longer crest on average than the nominate race, with a similar crest length to it at about {{convert|10|cm|in|abbr=on}}. It is monomorphic as is the nominate race, averaging paler and less streaky, but a similar appearance has been noted to birds from southernmost India are rather similar in appearance. The differences represented in this race from the nominate race are largely [[Cline (biology)|clinal]]. It is rather smaller than the nominate race. [[Wing chord (biology)|Wing chord]] length ranges from {{convert|351|to|370|mm|in|abbr=on}} in males and from {{convert|353|to|387|mm|in|abbr=on}} in females.<ref name= Ferguson-Lees/><ref name="Legge">Legge, W. V. (1880). ''A History of the Birds of Ceylon''. (4 vols in 1983). Dehiwala, Sri Lanka: Tisara Publishers.</ref>  Furthermore, in both sexes tail length is from {{convert|229|to|266|mm|in|abbr=on}} and tarsus length from {{convert|89|to|97|mm|in|abbr=on}}.<ref name= Naoroji/><ref name= Legge/><ref name="Ali">Ali, S., & Ripley, S. D. (1983). ''Handbook of the Birds of India and Pakistan: Together with Those of Bangladesh, Nepal, Bhutan and Sri Lanka''. Oxford University Press.</ref>

'''Crestless changeable hawk-eagle group'''
[[File:Nisaetus cirrhatus -Jurong Bird Park, Singapore-8a.jpg|thumb|A crestless changeable hawk-eagle (''N. c. limnaeetus'') in [[Singapore]].]]
* ''N. c. limnaeetus'' ([[Thomas Horsfield|Horsfield]], 1821): This race is found through the [[Himalayas|Himalayan foothills]] from [[Nepal]], northeast [[India]], via [[Burma]] to much of [[southeast Asia]] including the [[Malay Peninsula]] along [[Wallace Line]] to [[Philippines]] and the [[Sunda Islands|Greater Sunda Islands]]. This race can appear similar in size and build to the nominate race but unlike it is rather polymorphic and this is the most widely found of subspecies. This race's polymorphism is the source for the species being referred to as the changeable hawk-eagle.<ref name= Naoroji/> The pale morph of this race is still darker than the nominate race found further south in India. However, pale morphs from the Philippines tend to have a paler head and neck. Characteristically, this race is heavily streaked below, while juveniles look quite different as their head and underparts are largely white. Dark morph individuals tend to be chocolate-brown all over, although the tail base might appear lighter in flight.<ref name= Ferguson-Lees/><ref name= Ali/> Some birds of this race do have a vestigial crest of merely {{convert|1|to|3|cm|in|abbr=on}} in length but many appear to completely lack the crest. This race is generally similar in size to the nominate race but is more variable in size over its large distribution within the southernmost island birds averaging smallest while those found in the Himalayan foothills are arguably the largest hawk-eagles known in the species. [[Wing chord (biology)|Wing chord]] length ranges from {{convert|380|to|430|mm|in|abbr=on}} in males and from {{convert|405|to|462|mm|in|abbr=on}} in females. In limited samples, tail length was reported as {{convert|240|to|278|mm|in|abbr=on}} and tarsus length from {{convert|100|to|103|mm|in|abbr=on}}.<ref name="Baker">Baker, E.S. (1928). ''The Fauna of British India, including Ceylon and Burma. Birds. Vol. V. 2nd''. Edition. London.</ref> A sample of 6 females averaged {{convert|37.9|mm|in|abbr=on}} in the length of the rear hallux-claw, the main killing apparatus of most accipitrids, while 7 males averaged {{convert|32.3|mm|in|abbr=on}}.<ref name="Parry">Parry, S. J. (2001). ''The booted eagles (Aves: Accipitridae): perspectives in evolutionary biology''. University of London, University College London (United Kingdom).</ref>
* ''N. c. andamanensis'' ([[Robert Christopher Tytler|Tytler]], 1865): This race is found in the [[Andaman Islands]]. The subspecies is darker than the nominate subspecies and more similar to ''N. c. limnaeetus'' in hue but does not appear to have a full dark morph as is known in that race. Andamanian juveniles tend to have a  rather white head and underpart colour. A crest may variably be present but is usually only up to {{convert|5|cm|in|abbr=on}}. This race is small, a little smaller even than ''N. c. ceylanensis''. [[Wing chord (biology)|Wing chord]] length ranges from {{convert|330|to|375|mm|in|abbr=on}} in males and from {{convert|358|to|377|mm|in|abbr=on}} in females.<ref name= Ferguson-Lees/><ref name= Ali/>
* ''N. c. vanheurni'' ([[George Junge|Junge]], 1936): This race is native to [[Simeulue Island]]. It is similar in appearance to ''N. c. limnaeetus'', but apparently lacks a dark morph. The subspecies is also much less heavily blotched black on its whiter looking breast and never bears a crest. It is the smallest accepted subspecies of the changeable hawk-eagle, considerably smaller than ''N. c. limnaeetus''. [[Wing chord (biology)|Wing chord]] was measured as {{convert|312|mm|in|abbr=on}} in a single male and {{convert|329|to|337|mm|in|abbr=on}} in a small sample of females.<ref name= Ferguson-Lees/>