Editing Eastern imperial eagle (section)

==Description==
[[File:Kaiseradler Aquila heliaca 2 amk.jpg|thumb|left|Closeup of an adult imperial eagle.]]
The eastern imperial eagle is a large [[eagle]], but usually falls near the average size of the large-bodied genus ''[[Aquila (genus)|Aquila]]''. Adult total length can range from {{convert|68|to|90|cm|in|abbr=on}} with a typical wingspan of {{convert|1.76|to|2.2|m|ftin|0|abbr=on}}.<ref name= Ferguson-Lees/><ref name= Ali>{{cite book |first=Salim |last=Ali |year=1993 |title=The Book of Indian Birds |publisher=Bombay Natural History Society |location=Bombay |isbn=0-19-563731-3}}</ref><ref>{{cite web|url=http://europeanraptors.org/eastern-imperial-eagle/ |title=''Eastern Imperial Eagle'' |publisher=European Raptors |access-date=2020-11-20}}</ref> The average wingspan of a small sample showed males to average {{convert|1.95|m|ftin|0|abbr=on}} while a small sample of females averaged {{convert|2.07|m|ftin|0|abbr=on}}.<ref name= Brown>Brown, Leslie and Amadon, Dean (1986) ''Eagles, Hawks and Falcons of the World''. The Wellfleet Press. {{ISBN|978-1555214722}}.</ref> Although otherwise outwardly similar, the species displays [[Sexual dimorphism|reverse sexual dimorphism]] as do most [[birds of prey]], in which males are usually smaller than the females. For the eastern imperial eagle, females are up to 10% larger linearly and 40% heavier in body mass in some cases.<ref name= Ferguson-Lees/><ref name= Dimorphism>Katzner, T. E., Jackson, D. S., Ivy, J., Bragin, E. A., & DeWoody, A. (2014). ''Variation in offspring sex ratio of a long‐lived sexually dimorphic raptor, the Eastern Imperial Eagle Aquila heliaca''. Ibis, 156(2), 395-403.</ref> In terms of body mass, one survey found five males to weigh from {{convert|2.45|to|2.72|kg|lb|abbr=on}} and  five females to weigh from {{convert|3.26|to|4.54|kg|lb|abbr=on}}. The average weight of this sample of imperial eagles was reportedly {{convert|2.62|kg|lb|abbr=on}} in the males and {{convert|3.9|kg|lb|abbr=on}} in the females.<ref name= Ferguson-Lees/><ref name= CRC>''CRC Handbook of Avian Body Masses, 2nd Edition'' by John B. Dunning Jr. (Editor). CRC Press (2008), {{ISBN|978-1-4200-6444-5}}.</ref><ref>Louchart, A., Bedetti, C., & Pavia, M. (2005). ''A new species of eagle (Aves: Accipitridae) close to the Steppe Eagle, from Pleistocene of Corsica and Sardinia, France and Italy''.</ref> A sample of unknown size showed males to weigh an average {{convert|2.88|kg|lb|abbr=on}} while females reportedly weighed an average of {{convert|3.38|kg|lb|abbr=on}}.<ref name= Kirmse>Kirmse, W. (1998). ''Morphometric features characterizing flight properties of palearctic eagles''. Holarctic Birds of Prey. Merida and Berlin: ADENEX and World Working Group on Birds of Prey, 339-348.</ref><ref>Weick, F., & Brown, L. (1980). ''Birds of prey of the world: a colored guide to identification of all the diurnal species order Falconiformes''. Verlag Paul Parey.</ref> A further two mature females weighed an average of {{convert|3.56|kg|lb|abbr=on}}.<ref name= Brown/> Among standard measurements, males may range in [[Wing chord (biology)|wing chord]] length from {{convert|540|to|622|mm|in|abbr=on}}, in [[tail]] length from {{convert|260|to|308|mm|in|abbr=on}} and in [[Tibiotarsus|tarsus]] length from {{convert|91|to|98|mm|in|abbr=on}}. Meanwhile, females may range in wing chord length from {{convert|565|to|665|mm|in|abbr=on}}, in tail length from {{convert|270|to|330|mm|in|abbr=on}} and in tarsus length from {{convert|97|to|107|mm|in|abbr=on}}.<ref name= Ferguson-Lees/><ref name= Cramp/> A sample of imperial eagles ranged in total bill length from {{convert|65.7|to|76.5|mm|in|abbr=on}}.<ref>''Catalogue of the Birds in the British Museum Volume 1'' (1974).</ref>
[[File:Imperial Eagle (Aquila heliaca) (38741311735).jpg|thumb|right|An eastern imperial eagle, probably an older subadult, in flight showing their characteristic flat, relatively narrow wings.]]
In general, compared to other species in their taxonomic group, the eastern imperial eagle has a relatively long and thick neck, a big head and bill (with a gape line level with middle of eye), a longish square tipped tail, somewhat long and well-feathered legs and strong feet. The species tends to perch in a fairly upright position often on rather exposed tree branch or low mound, rock, haystack or similar convenient site. For an ''Aquila'' eagle, it is seemingly relatively less shy and bolder in the presence of humans.<ref name= Ferguson-Lees/> The adult plumage is largely a [[tar]]-like blackish-brown but for a well-demarcated and highly contrasting creamy to golden buff colour about the crown, hindneck and neck sides. Furthermore, adults have bold white ”epaulettes” on their shoulder braces, which are usually fairly conspicuous on perched birds. The adult's tail is narrowly dark barred over a greyish ground colour and has a broad black subterminal band, while a white tail tip sometimes manifest in adults that are freshly molted. The undertail coverts are sometimes indistinctly paler, rust to creamy, combined with grey tail base to give the appearance of a paler rear end.<ref name= Ferguson-Lees/><ref name= Forsman/><ref name= Clark>Clark, W. S. (1999). ''A field guide to the raptors of Europe, the Middle East, and North Africa''. Oxford University Press, USA.</ref><ref name= Forsman2>Forsman, D. (2005). ''Eastern Imperial Eagle plumages''. Alula, 11: 146-152.</ref> At rest, the wing tips tend to reach the tail tip.<ref name= Naoroji>Naoroji, R., & Schmitt, N. J. (2007). ''Birds of prey of the Indian subcontinent''. Om Books International.</ref> The juvenile eastern imperial eagle is mostly pale tawny-buff to sandy yellow with fairly heavy dark brown streaks from the throat down to the breast, mantle, scapulars and forewing coverts. The juvenile's scapulars and forewing coverts also have sometimes noticeable white tipped feathers while the median coverts are perceptibly browner and greater coverts blackish both with broad creamy-yellow tips forming clear wing bars. The flight feathers and tail on juveniles are often blackish and tipped whitish, however the white parts on the lower back to tail coverts are only lightly streaked in the centre and often not visible when perched. Below the streaked breast, the remainder of the juvenile's underparts are plain pale buff. By the 2nd year, the brown streaking on the underside fades to a plainer sandy hue and the pale bars also start to fade on wings. Especially later into the 2nd year into the 3rd year, some young eastern imperial-eagles show an erratic blotching of blackish-brown feathers below. By about the 4th winter, as the birds enter their subadult plumage, the forefront of the eagle is often a rather patchy mix of sandy and darker adult-like feathers. During slow annual molts, the dark feathers expand initially from the throat and upper breast outward. Late into the subadult stage, the birds also start to develop a pale crown and nape but usually the rear body still more juvenile-like, such as the pale rump-band and crissum despite the otherwise darkening tail and wing feathers. The full adult plumage is attained at 5–6 years of age but some subadults are already breeding before this.<ref name= Ferguson-Lees/><ref name= Forsman/><ref name= Clark/><ref name= Forsman2/><ref name= Bijleveld>Bijleveld, M. (1974). ''Birds of prey in Europe''. Macmillan International Higher Education.</ref>
[[File:Aquila heliaca, Hong Kong 1.jpg|thumb|right|An adult imperial eagle in [[Hong Kong]].]]
In flight, the eastern imperial eagle is a large raptor that has for an ''Aquila'' a very projecting neck and "huge" head and bill.<ref name= Ferguson-Lees/><ref name= Clark/> The long wings may appear fairly broad when compared to other, smaller raptors, but are relatively narrow with even parallel edges when compared to other ''Aquila'' eagles.<ref name= Forsman/><ref name= Forsman2/> Their flight style is relatively heavy but steady with deep powerful beats but they are not uncommonly clumsy at first takeoff.<ref name= Ferguson-Lees/> They tend to soar with forward pressed but rather flat wings, the outer wing feathers may sometimes curve up but as a rule they do not fly with a [[Dihedral (aeronautics)|V]] as do some other ''Aquila''. The species may also hold their wings flat while engaging in a glide but as it accelerates they may arch wings back. In flight, the adult from above shows dark brown with small white braces, greyish tail with fine dark bars and a very broad, blackish subterminal band. The adult is essentially all dark colored when seen from below relieved only by some very dusky grey flight feathers on the primaries (against the black wing tips), a grey crissum and thinly barred grey tail base. However, these features may be only obvious in good light and at reasonable distances.<ref name= Ferguson-Lees/><ref name= Forsman2/><ref name= Porter>Porter, R. F. (1981). ''Flight identification of European raptors''. A&C Black.</ref><ref name= Forsman3>Forsman, D. (2016). ''[[Flight Identification of Raptors of Europe, North Africa and the Middle East]]''. Bloomsbury Publishing.</ref> In flight, the juvenile is largely pale buff with brown streaking. The lower back, rump, tail coverts and leg feathers are all whitish cream in colour which contrasts noticeably with their white-tipped blackish greater coverts, primary coverts and quills. On their mantle, juveniles manifest two white wing bars above and a narrow whitish lower trailing edge. Meanwhile, the juvenile's inner primaries are much paler creamy-buff hue than their other flight feathers. The dusky brown wing linings of the juvenile plumage, when compared to the darker ones of adults, show more extensive coarse patterning. Some birds by 2nd to 3rd year are so worn in their flight feathers as to appear almost unstreaked sandy while, from the 3rd year on, darker feathers start to appear below with various untidy variations.<ref name= Ferguson-Lees/><ref name= Porter/><ref name= Forsman2/>

===Confusion of species===
[[File:Zoo19feb (65)a.JPG|thumb|left|A captive adult eastern imperial eagle sharing an aviary with a smaller cousin, the [[lesser spotted eagle]].]]
The eastern imperial eagle is typically smaller, being more slender and less bulky and powerful in appearance despite its proportionately larger head and longer neck, than the [[golden eagle]] (''Aquila chrysaetos''). In some parts of the range, the female imperial eagle probably averages similar size and body mass to the smaller male golden eagle. However, apparently the species can be reliably distinguished by the size of its [[Claw|hallux claw]] (the enlarged rear talon that accipitrids used as a killing apparatus) which is consistently larger in the golden species. Two female eastern imperial eagles measured {{convert|38|and|43|mm|in|abbr=on}} in hallux claw length while a male was about {{convert|35.5|mm|in|abbr=on}}, whereas the smallest talon measured for an immature male American golden eagle was {{convert|44.9|mm|in|abbr=on}}.<ref name= Ferguson-Lees/><ref name= Naoroji/><ref name= Brown/><ref>Bortolotti G.R. (1984). ''Age and sex size variation in Golden Eagles''. Journal of Field Ornithology. 55: 54–66.</ref> Nonetheless, besides its wider ranging golden cousin, this species is typically the largest, with the largest extremities (i.e. tarsal, tail and bill length) and most powerful [[Aquilinae|booted eagle]] species in the majority of its range (apart from its rare African winter range) when compared to similar eagles such as others in the genera ''[[Aquila (genus)|Aquila]]'' and ''[[Clanga (genus)|Clanga]]''.<ref name= Ferguson-Lees/><ref name= Forsman/><ref name= Naoroji/><ref name= Clark/> In their winter quarters in [[South Asia]], this species rivals a [[Pallas's fish eagle|fish eagle]] as the largest and most dominant eagle species.<ref name= Naoroji/> Usually, the plumage of the adult eastern imperial eagle is very distinctive. It is considerably darker than other adult ''Aquila'' eagles in central Eurasia. Furthermore, all other Eurasian eagles in their range lack the white spots on the wing mantle and greyish under-tail.<ref name= Ferguson-Lees/><ref name= Forsman/><ref name= Clark/> Given reasonable views, the juvenile imperial eagle is no less distinctive, with its unique tawny-buff covered in brownish streaking, a colour combination not seen in other species.<ref name= Clark/> From a distance, the juvenile may give the impression of a dark mantle and chest band with very pale rear body and a blackish tail and [[flight feather|remiges]] against strikingly pale primary wedges.<ref name= Ferguson-Lees/> Adults do however strongly resemble their considerably extralimital cousins, the [[Spanish imperial eagle]], but the eastern species has more restricted white on the shoulder and has a slightly more brownish hue in the dark underside feathers, while juvenile Spanish imperials are richly tawny in colour rather than pale buffy and lack brownish streaking on the body. The Spanish species is similar in size and proportions to the eastern imperial but is marginally heavier on average and has an even more protruding head and neck.<ref name= Ferguson-Lees/><ref name= HBW/><ref>González, L. M. (2016). ''Águila imperial ibérica – Aquila adalberti''. En: Enciclopedia Virtual de los Vertebrados Españoles. Salvador, A., Morales, M. B. (Eds.). Museo Nacional de Ciencias Naturales, Madrid.</ref>

The subadult eastern imperial eagle may be confused with older immature [[greater spotted eagle]]s (''Clanga clanga'') but the latter is less contrastingly patterned, without a paler shawl and has greater covert band below (despite the rare hint of one on some imperials) and densely bared flight feathers. Adult greater spotted eagles have similar underwing contrast as juvenile eastern imperial eagles but, beyond plumage characteristics, are distinct for their much smaller head, slightly smaller overall size and more compact frame with a relatively broader and shorter wings. More similar to the juvenile eastern imperial eagle is the ''fulvescens'' morph of the greater spotted eagle which is fairly rare (more so in the west) but is similarly or even as pale buffy. However this spotted eagle morph lacks the brownish streaks below of the juvenile imperial and further has contrasting much darker feathering on the wing coverts (heavily spotted in juvenile greater spotteds) and mantle as well as sometimes the facial feathers, and can further be distinguished by the same aforementioned differences in form.<ref name= Forsman/><ref name= Naoroji/> [[Indian spotted eagle]]s (''Clanga hastata'') tend to show paler lesser under-wing coverts like juvenile eastern imperial eagles but are considerably smaller and differ in all other proportions and plumage features.<ref name= Naoroji/> Although at times described as “very similar”, the eastern imperial eagles are fairly easily told from the [[golden eagle]] by being much darker with less broad wings that are held much flatter. The golden eagle, unlike imperial eagles, tends to fly with its wings pointed upwards and have a gradual tapering wing shape (somewhat narrower at the base, broader at the primaries). In golden eagles, the tail generally appears narrower and squarer in shape. At closer range, the pale area on the back of the head and neck in eastern imperial eagle may be suggestive to some of the golden eagle's golden nape but is always much paler and chalkier in colour, as well as more strongly contrasted by the otherwise dark feathers and is more extensive.<ref name= Ferguson-Lees/><ref name= Clark/><ref name= Naoroji/> Against the somewhat similarly sized but more compact juvenile [[steppe eagle]] (''Aquila nipalensis''), the juvenile eastern imperial eagle does not show a white band on underwing like the steppe. More obviously, the steppe eagle lacks the paler overall colours and contrasting brownish streaking of juvenile imperials. Feather wear can make the wing shape of the two resemble the other but the larger head and less compact frame of the imperial species render its flight profile distinctive.<ref name= Naoroji/> The only darker large booted eagle encountered by the eastern imperial eagle, in its African winter quarters, is the jet-black [[Verreaux's eagle]] (''Aquila verreauxii'') which is more suggestive in size and proportions of the golden eagle. An unlikely source of confusion, the Verreaux's differs in almost all plumage characteristics and has far more tapered wings that pinch in at the base and, like the golden eagle, tends to fly in a fairly strong [[Dihedral (aeronautics)|dihedral]].<ref name= Ferguson-Lees/> In [[Asia]], its proportions and size may be suggestive of the perhaps even rarer [[Pallas's fish eagle]] (''Haliaeetus leucoryphus'') and the two can potentially be mistaken in strongly backlit conditions which obscure their obviously distinct plumages.<ref name= Naoroji/> The large headed and flat winged shape of the imperial eagle may too suggest in silhouette the [[white-tailed eagle]] (''Haliaeetus albicilla'') but that species is usually rather larger bodied and even larger headed with much broader wings and a proportionately shorter tail.<ref name= Ferguson-Lees/><ref name= Forsman3/> [[Cinereous vulture]] (''Aegypius monachus''), being similarly dusky overall below, have been suggested as confusion species, but are much larger than imperial eagles with differing proportions (far broader wings, proportionately smaller head and shorter tail) and lack any of the contrasting pale parts of the imperial eagle's plumage.<ref name= Ferguson-Lees/>

===Vocalizations===
[[File:Kaiseradler Aquila heliaca 4 amk.jpg|thumb|A probable older subadult eastern imperial eagle in a captive [[falconry]] centre.]]
The eastern imperial eagle is quite vocal on their breeding ground but tends to be silent or nearly so elsewhere. The main call of the species is a deep, harsh bark ''owk owk'', ''gok gok'' or ''kraw-kraw''. The call tends to be repeated rapidly up to 8-10 times. Their call is perceptibly deeper and harsher than that of the [[golden eagle]], somewhat incongruously also being more resonant and commanding. Sometimes when extending to a prolonged version, its call is sometimes considered reminiscent of the croak of a large [[frog]].<ref name= Ferguson-Lees/><ref name= Gould>Gould, J., & Rutgers, A. (1966). ''Birds of Europe (Vol. 1)''. Methuen.</ref><ref>Schulze, A., & Dingler, K. H. (2003). ''Die Vogelstimmen Europas, Nordafrikas und Vorderasiens''.</ref> The eastern imperial eagle most frequently calls during their aerial displays. In extreme cases, the call may be repeated up to 13 times during an aerial display. Furthermore, they may repeat the call from a perch. Females may also call when a male arrives with prey. Alarm calls recorded for the species include a soft ''ko-gok, wk wk wk'', uttered in response to a distant intruder, a closer approach also may cause a harder ''gek'' call by the mother. A rising and falling trill has been additionally recorded in captivity is also probably an alarm call.<ref name= Ferguson-Lees/><ref>Boswall, J. (1969). ''New Palearctic bird sound recordings during 1966-67''. Diemer & Reynolds.</ref>