Greater spotted eagle

Adult wintering in Oman.

Greater spotted eagles are members of the subfamily Aquilinae, or the booted eagles, a monophyletic group within the larger Accipitridae family. All booted eagles have feathers covering their legs. Members of this diverse, wide-ranging family may be found on every continent except Antarctica. Thirty-eight species of booted eagle are recognized.[2][4][12]

Booted eagles are often grouped with the genera Buteo and Haliaaetus, and other more heavy-set Accipitridae, but they may be more closely related to the more slender accipitrine hawks than previously believed. The greater spotted eagle's closest living relative is the lesser spotted eagle; they seem to have diverged from their most recent common ancestor around the middle Pliocene, perhaps 3.6 million years ago (mya). This "proto-spotted eagle" probably lived in the general region of Afghanistan, and split into northern and southern lineages when both glaciers and deserts advanced in Central Asia as the last ice age began. The northern lineage subsequently separated into the greater (eastern) and lesser (western) spotted eagle species of today, probably around the Pliocene-Pleistocene boundary almost 2 mya.[13][14][15]

The spotted eagles were long classified as part of the genus Aquila, along with several other mostly large, brownish eagles.[4] However, molecular phylogenetic studies using DNA sequences of one mitochondrial and two nuclear genes showed that the spotted eagles form a monophyletic group with each other and the long-crested eagle (Lophaetus occipitalis). Studies suggest that the spotted eagles should be grouped with Lophaetus, or that all of these species should be grouped within Aquila.[2][3][16] Furthermore, a close relationship has been found between the spotted eagles and the black eagle (Ictinaetus malaiensis) native to Asia. The spotted eagles, long-crested eagle and black eagle may comprise a species complex or clade.[17] The spotted eagles were ultimately reclassified as a distinct genus, Clanga, due to overwhelming genetic evidence and large divergences in morphology and ecology between spotted eagles and their sister taxa.[17][18]

The extensive hybridization between the greater spotted eagle and the lesser spotted eagle may occur because, despite a significant genetic difference between the species, they have one of the closest relationships of any closely studied accipitrid taxa.[17][18][19] The mitochondrial genetic sequences of these species have more than 3% divergence, about twice what is considered the minimum genetic difference to distinguish two species.[20] A third spotted eagle, the Indian spotted eagle (Clanga hastata), was recognized as a distinct species from the similarly sized lesser spotted eagle in 2006.[15][21] The scientific name clanga may derive from Ancient Greek κλαγγή, "scream,"[22] or its root may be the Greek word klangos (a variant form of plangos) for "a kind of eagle" mentioned by Aristotle.[5]

A juvenile greater spotted eagle wintering in India exhibits the highly distinct fulvescens morph plumage.

Museum specimen of juvenile

The greater spotted eagle is a rather large and compact eagle. Normally, it is black-brown with a contrasting yellow beak. This species has a short neck with a large, often rather shaggy-naped head, strong beak, and a short gape-line with round nostrils. The wings are broad and long, reaching the tail tip. The tail is relatively short and rounded.[4][7] The overall effect of the broad wings and short tail can give them an almost vulture-like silhouette. The feet are large, and the feathers covering the legs are less compactly arranged than on lesser spotted eagles.[4][5]

Greater spotted eagles tend to perch in the open. Most perches are on treetops at a forest edge, or more isolated vantage points such as a bush, utility pole or a steep river bank. It is not uncommon for greater spotted eagles to forage from the ground or rest there in a somewhat hunched posture.

Adult greater spotted eagles are generally a rather uniform dark brown to blackish brown, though the coloration may appear purplish and glossy. They may appear more starkly contrasted when freshly moulted.[4][5]

The upperwing coverts are often a shade paler than the rest, though these eagles generally appear uniformly dark with two contrasting features: a pale beak and a narrow white U above the tail, though this is usually concealed at rest. The species is dimorphic or even polymorphic. Pale and intermediate phenotypes are rare, although can be slightly more common farther east.[4][23]

For pale adults (sometimes referred to as Clanga clanga fulvescens), the plumage is bicolored. The tail, flight feathers, and greater wing coverts are all blackish, with the body and the rest of the wing coverts appearing light yellow or pale golden buff, sometimes becoming creamy when aged. The buff colour of the fulvescens phenotype is usually contrasted with diffuse dark colouring around the eyes, on the leading edges of wings, and more rarely and sparsely on the chest.[4][24] Intermediate and other variants are very rare, but include those with a slightly paler body and variable yellowish-brown streaking or mottling on the fore upperwing coverts (which can make them look similar to juvenile lesser spotted eagles), or mottled yellow-brown with a dark-streaked breast and pale-tipped wing coverts (like the juvenile eastern imperial eagle (Aquila heliaca)). These intermediate types may show the typical dark brown to black on the upper body, but in flight display pale mottled grey wing linings, or even normal coloration apart from the contrasting paler underbody.[4][5][24]

The juvenile greater spotted eagle is generally uniformly black-brown with whitish to yellowish drop-shaped spots. Some juveniles appear very heavily spotted all over, others less so, but they always show an obvious row of spots along the upperwing coverts, forming clear wing bars tail and flight feathers, except the outer primaries. The feathers underneath on juveniles are often broadly cream tipped, often showing some buffy streaks below, especially on the flanks and trousers. In fulvescens type greater spotted eagles, juveniles are like the pale adult but show the typical heavily spotted wings and tail of typical juveniles and often show some darker centers to the scapulars and median coverts. By the 2nd-3rd year, the plumage is often considerably worn but white tips still create sufficiently prominent wing bars (unlike in lesser spotted eagles) until the 2nd winter, when most coverts are then newly molted and with smaller pale tips. In subsequent immatures, from about the middle of 3rd year on, the plumage is more adult like with few or no indistinct spots left, but remiges are of unequal age and untidy looking.[4][24] The subadult is generally more uniform but often still shows some pale tips to the greater coverts.[4] Maturity is obtained by about the fifth year, though sometimes they may not breed until the sixth.[4][25] The bare parts change little in colour at different ages, with eyes being dark brown, while the beak and feet are yellow in all ages. This is a large, dark raptor in flight often looking bigger even than its true size, with well protruding head, quite long wings (which often look shorter due to their broadness), slightly bulging secondaries and rather squared seven-finger tips, although juvenile wings can look more rounded.[4] On the wing, greater spotted eagles appear heavy bodied, which often is suspended below wings and relatively short broad tail. Comparatively, they tend to have quick wing beats with little upstroke and appear to have comparatively lighter flight actions than steppe eagles (Aquila nipalensis), but they appear somewhat more heavy, less graceful and less Buteo-like than lesser spotted eagles.[4] Greater spotted eagles soar on almost flat wings, with hand often slightly lowered and the primaries well spread. When gliding, the wings are bowed with a clear angle between arms and hands, emphasizing the short look of wings.[4]

On their upperwings, greater spotted eagles variably show a pale primary patch formed mainly by white based shafts and partially pale outer webs on all ages, but much smaller and less obvious on adults.[4] The underwing almost invariably has a single white crescent formed by white base of outermost three primaries, secondaries and innermost primaries with nine to eleven dense narrow dark bars fading toward wing tips, these visibly only at close range.[4] When seen in flight, the normal adult is uniformly blackish with a faint pale U above tail, barely paler wing coverts and paler quills. It is not unusual to have slightly paler wing linings similar to lesser spotted eagles but only one, not double, whitish crescent at the base of primaries. In fulvescens/pale morph adults, most of the wing coverts on both surfaces and body are contrastingly buffy to tawny.[4][26] Juveniles on the wing normally appear very dark with liberal spotting both above and below, though some juveniles appear with spots restricted to wings, scapulars and trousers. All juveniles when seen well always show the characteristic white end spots on wing coverts forming two to three wing bars.[4] Otherwise, the juvenile has a creamy trailing edge to the wings and tail. Below juvenile greater spotted eagles have largely black (apart from the creamy crissum) wing linings contrasting with paler greyer-soot flight feathers. Other juvenile plumages are variably paler but with quills as those of a typical juvenile.[4] The birds that breed in the Ural-Volga area are slightly larger and more muted in plumage characteristics and slightly smaller sizes in the species seem to be prevalent farther west, i.e. Europe. There appears to be a near 5% size difference in favor of Indian wintering birds over Middle East ones.[27]

Size

Greater spotted eagles are large raptors and medium-sized eagles.

The greater spotted eagle is a medium-sized eagle and a large raptor.[7] Despite their similar plumages, this species shows strong sexual dimorphism in favor of the female. The size difference is up to 26% linearly and females not uncommonly can be as much as twice as heavy as the males, making them rival the martial eagle (Polemaetus bellicosus) as perhaps the most sexual dimorphic member of the Aquilinae on average.[4][7] However, on the contrary, some of the largest male greater spotted eagles can overlap in most linear and mass measurements with smaller females.[24][28] Total length of full-grown greater spotted eagles can vary from 59 to 74 cm (23 to 29 in).[29][30] In wingspan, males have been reported to measure 155 to 177 cm (5 ft 1 in to 5 ft 10 in) while females can measure from 167 to 185 cm (5 ft 6 in to 6 ft 1 in).[7][29][31][32] Body mass for males has been reported as ranging from 1,537 to 2,000 g (3.389 to 4.409 lb).[7][28] [33][34] Females have been found to range in body mass from 1,820 to 3,250 g (4.01 to 7.17 lb).[7][28] [34] Among standard measurements, wing chord can range from 477 to 519 mm (18.8 to 20.4 in) in males and from 507 to 545 mm (20.0 to 21.5 in) in females.[7][4][33][35] The shortish tail varies from 227 to 249 mm (8.9 to 9.8 in) in males and from 235 to 268 mm (9.3 to 10.6 in) in females.[4] The fairly long tarsus is from 97 to 105 mm (3.8 to 4.1 in) in males and from 96 to 112 mm (3.8 to 4.4 in) in females.[4][36] Reportedly, the culmen length can range from 32.5 to 39 mm (1.28 to 1.54 in).[37]

Identification

A characteristic young greater spotted eagle, showing its dark colouring and extensive white wing markings.

Despite a fairly unique appearance, field identification of greater spotted eagle can be quite difficult.[39] Primarily this species is told from lesser spotted eagles by structure and proportions, though distant birds may be practically indistinguishable.[4][23] The adult compared to the lesser appears very broad winged, which in turn makes the head look relatively small, however it is important to remember that greater spotted juveniles can appear less bulky looking, narrower and more rounded along the wing and longer-tailed making their proportions closer to the lesser.[4][23] Size can be clearly larger in the greater spotted eagle, with female greater spotted eagles effectively dwarfing most lesser spotted but there is a very broad size overlap between the two spotted eagle species, and in some cases male greater spotteds can be scarcely larger than even male lesser spotted eagles.[4][5] Side-by-side, it is fairly conspicuous how much darker a pure greater spotted eagle typically is than a lesser spotted eagles.[29][23] Greater spotted eagles, when compared to the lesser spotted eagles, are notable for their lack of nape patch, dark uppertail coverts, blackish-brown uniform arms, or uniform, dark upperwing coverts (not contrastingly rusty brownish).[23] Some intermediates are difficult to tell from young lesser spotted eagles, but can be told by the greater spotted eagles intermediate’s usually darker wing linings, morphology, differences in appearance of primary patch and carpal arc.[4] The juvenile usually lacks pale nape patch of the lesser spotted eagle, but it is sometimes present "albeit only slightly paler than rest of plumage and never ochre or orange".[40] Typically the spotting and barring pattern is much stronger in juvenile greater than in lesser spotted eagles but this is not always reliable.[23] The hybrids of the two spotted eagles can be more difficult to distinguish, and are often muddled and varied in appearance, some hybrids being much closer to one species or the other.[23] Pure greater spotted eagles can be told from pure lesser spotted eagles via in-hand measurements such as bill height, width and extent of white spots on the juvenile, and the length of middle toe.[41][42] The greater spotted eagle on the Indian subcontinent might be confused with Indian spotted eagles, more so greater spotteds in faded plumage.[5] The Indian species is smaller (of a size or slighter even than the lesser spotted eagle), somewhat narrower-winged and longer-tailed than the present species, with primary fingers more deeply cut and square ended. The Indian species has a more distinct pale window in primaries, paler and less distinctly streaked underparts, and paler upperparts (more like a steppe eagle in colour) with less distinct, more diffuse pale tips to the larger wing-coverts. Furthermore, the Indian spotted eagle has a notably deeper gape extending behind its eye.[5][29]

From non-spotted eagles of similar or of larger sizes, the greater spotted eagle tends to be fairly compact in features with proportionately broad (and short-looking) wings, a shortish tailed and an overall darker and distinct patterned plumage.[5] One rather similar eagle is the steppe eagle which is larger and bulkier than the greater spotted eagle. Compared to the steppe eagle, the greater spotted eagle has a shorter neck, smaller bill with a shorter gape line, no pale nape patch (seen in adult steppe), narrower and less baggy trousers, and generally much shorter, slightly broader wings. At a distance they can look quite alike, but in favourable light you may look for the steppe eagle's bolder, more extensively barring on the greyer flight feathers, complete lack of carpal arcs below, paler throat and above paler nape and larger but more diffuse primary patch.[4][29] Greater spotted eagles of the fulvescens and intermediate morphs resemble a large number of eagles, but can be distinguished by underwing colour and pattern such as their distinct carpal arc and thinly dark barred quills, from pale or intermediate morph of the similarly sized tawny eagle (Aquila rapax), which is usually less dark backed without the defused dark face and possessing more typical, less broad wing proportions. Juveniles of the eastern imperial eagle can resemble fulvescens greater spotted eagles but are larger and clearly structurally different. The imperial has much longer and narrower wings, a longer neck, a bigger, more prominent beak with an oblong (rather than oval) nail, a longer and narrower gape line, more conspicuous pale inner inner primaries, no carpal arc, a brown-streaked breast (though greater spotteds can show some diffuse marks), unmarked tarsal feathering, pale irides and obvious pale window on inner primaries.[4][43] Against the paler morph greater spotted eagles, beyond structural dissimilarities, subadult steppe eagles can be told by the thicker well-spotted quill bars and paler underwing diagonal.[4] In the eastern portion of range, they can be told apart from the even darker black eagle with that eagle being much slimmer with paddle-shaped wings and long and clearly barred tail.[4]

Underside of adult wintering at Bharatpur (Rajasthan, India).

Upperside of adult wintering in Bharatpur (Rajasthan, India)
Note light wing stripes.

Greater spotted eagles are almost entirely migratory birds. However, it is not considered a long-distance migrant compared to other birds of prey.[93] They migrate between late August to October, occasionally lasting into November. The return spring flight typically starts in early February, peaking in March and ending in April.[4][19][56][94] However, migration has been documented well into May, near the Bosphorus in Turkey.[95][96] Migration on average peaks earlier in the eastern end of their range, such as in Bhutan, where the largest numbers are seen in late February.[97][98][99] They migrate later (by around 2 weeks) than lesser spotted eagles and return earlier than that species as well. At known migration stopovers, lesser spotted eagles almost always outnumber greater spotted eagles.[7][29][100] Greater spotted eagles who breed in Europe may migrate to southern France, especially Camargue, down to Spain, Italy, and sometimes Sweden. Western breeding birds also regularly wind up in North Africa, with a few in Morocco, Egypt, the Nile Valley, Sudan, Ethiopia, and occasionally points further south. Birds from various origin sites may wind up in the Middle East (mainly Arabia), South Asia (from Pakistan, most often Punjab and Sind, northern India, and Nepal), east to Indochina, the Malay Peninsula, and southern and eastern China.[4] Predominantly, migrating greater spotted eagles on an East European track migrate to the Middle East or Northeast Africa, while other migrate through the Carpathian Mountains to the Balkan Peninsula and thirdly through Central Europe and Western Europe to Southwestern Europe.[93] The main wintering sites of the Asian populations are located in the Arabian Peninsula, the Indian Subcontinent, the Indochina Peninsula and East China.[93] During migration, greater spotted eagles commonly cover around 150 km (93 mi) per day but can cover up to 350 km (220 mi) within a day.[101][102] The flight speeds of migrating eagles of the species was documented as 26.6 to 45.5 km/h (16.5 to 28.3 mph) in the Baikal region, with peak movements times from noon to 6:00 PM.[103]

There’s limited information on discrepancies in how different ages and sexes migrate but in Malaysia, immatures outnumbered adults six to one.[104] At Lake Baikal, 96% of migrating greater spotted eagles were observed to be adults, a concerning imbalance per researchers.[103] It is said that lesser numbers are generally recorded in spring migration compared to autumn passage.[7] Generally migrants of the species move on broad fronts in singles or pairs, large groups considered as up to 10 in northbound over Bhutan in late February. Greater spotted eagles tend to be scarce at traditional migratory bottlenecks such as Bosphorus and the straits of the Red Sea.[4][95] Old claims of as many as a thousand migrating eagles in the fall at Bosphorus are possibly erroneous (although there’s possibly been a reduction of up to 75% from what was once the peak migrating numbers).[7] In South Baikal in Irkutsk Oblast within Russia, greater spotted eagles accounted for only 0.2% (7-34 individuals annually; 137 individuals over 8 years) of the observed migrating raptors in autumn migration.[103] The largest (modern?) counts have been found to be 86 and 74 at Suez in Egypt in autumn and spring, respectively, with smaller numbers recorded crossing into Africa at Bab-el-Mandeb, although a maximum of 85 has been recorded in northern Israel in autumn.[94] An adult captured near Mecca in western Saudi Arabia in late October was radiotracked 850 km (530 mi) to Yemen, where it spent from late November-early February, before returning 5,526 km (3,434 mi) via southern Iraq, across the Iranian highlands, skirting the south edge of the Aral Sea back finally to the Siberian breeding area near Omsk, covering 4,516 km (2,806 mi) of return journey in less than a month.[4] Satellite tracking has of an Estonian breeding bird confirmed it consistently used the same wintering ground in coastal Catalonia, eastern Spain, over 7 consecutive years.[94] Despite some individual devotedness to wintering grounds, one radiotracked individual initially trapped in the United Arab Emirates was found to go to Pakistan instead the following winter from its Kazakh breeding grounds, showing some variability in this regard.[105] A wintering greater spotted eagle in southwest Saudi Arabia (from a Western Siberia breeding area) was found to utilize an average home range in winter of 65 km² (25 sq mi), which contracted 24% before it migrated in the spring, taking from late February to late April to complete its over 5,500 km (3,400 mi).[106] The southernmost record of the greater spotted eagle ever was one that traveled 9,270 km (5,760 mi) from the Polish Biebrza National Park to Zambia in southern Africa.[107] Several other purportedly greater spotted eagles were tracked to several areas of Africa but nearly half were actually hybrids with lesser spotted eagles and were migrating in more typical fashion and location to that species.[102] Improbably, at least seven records show immature greater spotted eagles staying through the summer in Saudi Arabia.[96] Similarly, records show lingering numbers of this species in at least May in Peninsular Malaysia.[82]

Large water-dwelling rodents such as European water voles are significant food for breeding greater spotted eagles along with smaller upland vole species.

This species hunts mainly on the wing, quartering over relatively open ground a bit like a harrier or soaring high above, dropping or diving steeply when prey is spotted.[4][5] Brown & Amadon describe the hunting greater spotted eagle as "Although not a very active species it is not exactly sluggish, and on the wing it has the look of a true eagle".[7] Greater spotted eagles will scatter waterfowl by stooping low over their flock, then selecting isolated individuals for attack.[4] Sometimes the greater spotted eagle still-hunts from a perch, a method more commonly employed by other eagles of similar distribution, and often hunts on foot as well. It mostly takes prey on ground or on the water.[4][5] Also some kleptoparasitic attacks are carried out on other birds of prey.[4] Although scavenging for carrion seems to occur almost aseasonally, it is likely rather more prevalent during non-breeding times, with mostly fresh prey brought to greater spotted eagle nests.[6][5] Greater spotted eagles are attracted often to grass fires and swarming locusts, often along with other predators such as steppe eagles, during non-breeding times.[4] During the breeding season in Biebrza National Park in Poland, hunting behaviours were studied. It was found that the peak flying and hunting times were 10:00 AM to 2:00 PM, with the eagles rarely flying before 9:00 AM and often in repose from 2:00 to 4:00 PM. Prey deliveries may have been more varied when involving the male, the main food provider, than later into the season when the female resumed hunting. In Biebrza, hunting territories defended from conspecifics as well as lesser spotted eagles and other large birds of prey. Per the Biebrza data, the hunting success was 34% for the male up to mid-July after which success declined to 20%.[108] The hunting success rates of greater spotted eagles seems to rather high, as aforementioned 34% for much of the breeding season, which is much higher at comparable times than golden eagles (Aquila chrysaetos), which has a hunting success rate of around 20%, lesser spotted eagles with a success rate of 24% and somewhat higher than Bonelli's eagles (Aquila fasciata), at a 28.5% hunting success rate.[109] Pellets are considered the most reliable way to determine greater spotted eagle foods as prey remains alone can be biased towards birds.[29]

The greater spotted eagle is a slightly opportunistic predator but tends to favor rather particular prey types.[5] The diet tends to be composed mostly of small mammals.[4] There is some dietary similarity to the better-known lesser spotted eagle but the greater spotted includes more birds in foods and favors larger prey.[4] Beyond mammals and birds, the greater spotted eagle will sometimes prey on amphibians, reptiles (mainly small-to-mid-sized snakes) and occasionally small fish and insects.[4][24] As can be expected by their habitat preferences, they tend to focus on vertebrates that are associated with water.[4][19] Generally its prey spectrum is somewhat diverse, at slightly fewer than 150 known prey species, more diverse than the known diet of steppe eagles, similar in diversity to that of the lesser spotted eagle but possibly about half as diverse of the diet of the eastern imperial eagle.[6][5][110][111] It is sometimes stated that they tend to take prey mostly up to only 250 g (8.8 oz).[4] This was backed this up via estimations from another source that around 22% of the diet will weigh 63 g (2.2 oz) or less, 37% of diet will weigh 63 to 125 g (2.2 to 4.4 oz) and around 30% will weigh 125 to 250 g (4.4 to 8.8 oz) and that generally most prey will weigh under 1,000 g (2.2 lb). Based on this source, the mean estimated prey size for the greater spotted eagle may fall around approximately 157 g (5.5 oz).[9] A large food study from Belarus found that 41.9% of prey had a body mass of 51 to 200 g (1.8 to 7.1 oz) and 38.3% was made by prey estimated at 11 to 50 g (0.39 to 1.76 oz); however, the primary source of prey biomass was from prey weighing 601 to 1,200 g (1.325 to 2.646 lb) at 34% of the biomass and prey weighing over 1,200 g (2.6 lb) made up 16% of the biomass.[110] The mean estimated size of male prey deliveries in an Estonian study was merely 57.8 g (2.04 oz).[112] This is as opposed to study from Belarus where the mean estimated size of prey deliveries by males was 161.2 g (5.69 oz).[110] The mean prey sizes are roughly similar to those of larger steppe eagles and somewhat higher than those of lesser spotted eagles, which tended to heavily focus on prey weighing under 63 g (2.2 oz) weight range of prey (around 60% of diet), however most Aquila eagles tended to take prey typically that were slightly to considerably higher in weight than the prey typical of greater spotted eagles.[9] However, sometimes the greater spotted eagle is credited with successful attacks on large prey.[5][19]

In the largest known food study for greater spotted eagle the diet was studied in 3 different habitats in Belarusian Polesia, from natural to mixed to modified habitats. 797 prey items were identified total, but often not to species. Many, surprisingly, were unidentified invertebrates which made up 15.8%, with beetles (also unidentified to species) being a further 14.9%. Assorted Microtus voles were important in Polesia, namely the common (Microtus arvalis), tundra (Microtus oeconomus) and East European voles (Microtus mystacinus) made up collectively 23.4% of the diet by number. Other significant prey were European water vole (Arvicola terrestris) at 8.9%, common snipe (Gallinago gallinago) at 4.1%, mallard (Anas platyrhynchos) at 3.3%, water rail (Rallus aquaticus) 3.1%, unidentified small passerines 2.9%, spotted crakes (Porzana porzana) 2.6% and grass snakes (Natrix natrix) 2.3%. Significant in biomass but less so to numbers were the northern white-breasted hedgehog (Erinaceus roumanicus), European mole (Talpa europaea), Anas dabbling ducks, grey herons (Ardea cinerea), Eurasian bitterns (Botaurus stellaris) and black grouse (Lyrurus tetrix), with very small numbers of very large birds being taken. Bird prey in Polesia made up 68% of the diet, mammals 25.3%, reptiles 3.4%, fish 3% and amphibians 0.3%.[110] Of 102 prey items in the Belarusian Smolenskoye Poozerye National Park, 38.2% were European water voles, 7.8% were European moles, 5.9% each Sorex shrews, Microtus voles, and unidentified passerine species and 8.7% were common frogs.[113] At a nest in Estonia, of 105 visually identified prey items, Microtus species and further unidentified rodents comprised some 63% by number, however they made up only 28% by biomass, while birds formed only 19% numerically but 56% of biomass.45% of avian prey species were medium-sized, e.g. hazel grouse (Bonasa bonasia), grey partridge (Perdix perdix), northern lapwing (Vanellus vanellus) and hooded crow (Corvus cornix).[112] Other European studies have been largely confined to wintering greater spotted eagles. In the Amvrakikos Wetlands of Greece, 95 prey items were determined, being composed almost exclusively of water birds. The main prey here were common teal (Anas crecca) (17.9% by number, 15.9% by biomass), common moorhen (Gallinula chloropus) (16.8% by number, 14.9% by biomass), Eurasian wigeon (Anas penelope ) (11.6% in number, 27.4% in biomass), unidentified Anas ducks (5.3%, 7.8% in biomass), Eurasian coot (Fulica atra) (4.2% by number, 8.7% by biomass) and little egret (Egretta garzetta) (3.2% by number, 4.7% biomass), with a smallish contribution by ground beetles, passerines and snakes.[114] Over 8 years of study in Natural Park of El Fondo in the Spanish Province of Alicante almost entirely large prey was taken here, i.e. few to none small rodents such as voles. Among the 100 prey items found, the main prey were common moorhen (23.1% by number, 15.2% in biomass), common teal (8.97% by number, 6.44% by biomass) and black rat (Rattus rattus) (7.69% by number, 3.01% by biomass), with unidentified Rattus making up 7.69% by number, 2.76% by biomass. Other notable regular prey here were black-headed gull (Chroicocephalus ridibundus), Eurasian coots and northern lapwing (Vanellus vanellus), while large prey, making up much of the biomass were common carp (Cyprinus carpio) at 18.9% of biomass, grey heron at 11.7% of biomass and European rabbit (Oryctolagus cuniculus) at 9% of the biomass.[115]

In nests in Western Russia, a mean total of 53% of the diet was small mammals and 45% was birds.[112] The diet upon study in the Leningrad region was led by European water vole at nearly 51% of 79 prey items followed by introduced muskrats (Ondatra zibethicus) at 13.9% of diet and common teal 3.8% of diet, with 20.2% of diet made up of by frogs, most probably common (Rana arvalis) but also some moor frogs (Rana temporaria).[116] 322 non-carrion prey items were found for greater spotted eagles in the Belaya River, 59% of which were mammals. The diet was largely European water vole at 32.6%, followed by smaller voles and mice. It was found that the Belaya eagles ate a large balances of reptile prey, which were found to comprise 19.5% of the diet. 15% of all vertebrate prey, in fact, was European adders (Vipera berus), adders and grass snakes being the primary reptile prey. The greater spotted eagle took average sized snakes and were not seen to prey on small snakes, nor to take many particularly large snakes, usually with the snake sizes estimated at up to 40 to 45 cm (16 to 18 in) long, occasionally 60 cm (24 in) or more. The eagles in Belaya are often seen grasping snakes about the head. In Belaya, only 6.5% of the diet was birds and they were mainly significant only in the Oka Nature Reserve and the eagles of the region occasionally partook in carrion feeding, including moose (Alces alces) carcasses.[117] In a compilation study from the Volga region, Ural Mountains and Western Siberia, 74.7% of the diet was mammalian in 482 prey items in the regions. The main prey species was the European water vole at an average of 32.4% of diet (28.1-36.8%), followed by common vole at avg 11.4% (0-17%), tundra vole at 6.2% (1.9-16.9%), birds comprised about 16% of diet, most importantly Eurasian coots and Podiceps grebes, followed by rooks (Corvus frugilegus).[6] In the Tyva Republic, more terrestrial, upland hunting can be projected since the Daurian pika (Ochotona dauurica) was reportedly the main prey for greater spotted eagles. Similarly, in Khakassia, the greater spotted eagle were said to hunt mostly the long-tailed ground squirrel (Spermophilus undulatus), the only area known where ground squirrels were said to be preferred over voles in breeding areas for these eagles.[118]

Water birds such as common moorhens are a common component of the diet of greater spotted eagles in almost any season.

The diet is generally more erratically known in non-European wintering areas, while, like many other raptors of similar region, migrating greater spotted eagles typically fast until they reach their wintering terminus point.[7][5] The most well-studied Asian wintering population of the species in terms of dietary behaviour is likely in Bharatpur in India, particularly in Keoladeo National Park. It was found that the greater spotted eagles here occupied a greater range of habitat than other spotted and Aquila eagle. Winter numbers are up to 30 for this species, with them recorded to exploit the full 9 km (5.6 mi) length of the local marshland, their numbers peaking in November and December and then diminishing after January. Here greater spotted eagles are non-territorial and free ranging. Like most other wintering migrant raptors here, the greater spotted eagle becomes a highly opportunistic feeder that shows a preference for easily attainable foods, akin to the milvine kites they often overlap with in the winter quarters. The greater spotted eagles regularly come down to carrion, pirate food from other birds, feed on stranded fish and, perhaps most regularly, hunting and taking young herons, storks and other water birds from heronries. When regularly hunting around them, the greater spotted eagles often approach the heronry in a hover, creating tumult throughout the heronry, as the heronry settles they often suddenly drop onto singled out nest, the eagle defeathers the squab (nestling water bird) on the nest itself and commences feeding. The Bharatpur greater spotted eagles tend to shows a slight preference for slow moving prey, but also takes fast flying birds like waders and ducks and often tests flocks of coots with low flights over water and continually "buzzing" the birds until an opportunity presents itself via an individual isolated. Often perches extensively on a favorite lookout post with Acacia nilotica favored in Bharatpur. Some possible nighttime hunting has been inferred for greater spotteds in Bharatpur but they typically hunt by day. During inclement weather in Bharatpur, the eagles may pause hunting. As many as 7-10 greater spotted eagles are attracted by a conspecific’s heronry kill and subsequently often jostle each other. Often this results in the eagle’s accidentally drop the kill into the water, though those dropped onto dry ground frequently become food for wild boars (Sus scrofa) and golden jackals (Canis aureus). In one case, two adult greater spotted eagles and a single immature eastern imperial eagle destroyed at least 30 water bird nests in a single day. Out of 79 hours of observation on greater spotted eagles, 49% of the time was spent foraging, increasing to 72% by March due to scarcer foods. Meanwhile, they spent 26.4% of observed time resting and 20.6% of the time soaring, with soaring rising to 35% in February. The greater spotted eagles consumed a daily mean of 240 g (8.5 oz) per day, with most foods nourishing them over several days, and they reportedly hunted the most diverse prey range of any raptor of the region.[5][119][120][121][122] In the general Indian subcontinent, greater spotted eagles are known to freely scavenge carrion, as well as to feed on small wetland dwellers such as frogs, especially Indus valley bullfrogs (Hoplobatrachus tigerinus), and chameleons and Calotes lizards on land nearby. A general aptitude in the region has been reported for avian prey, largely larger rails such as moorhens, Eurasian coots and gray-headed swamphens (Porphyrio poliocephalus), as well as waterfowl and (mostly young) storks, herons and egrets; however upland birds such as rufous treepies (Dendrocitta vagabunda), Eurasian collared doves (Streptopelia decaocto) and Indian rollers (Coracias benghalensis) seem to be in the spectrum there too. Though rare at large carrion, greater spotted eagles in the Indian subcontinent seem to be attracted to terrapins maimed or partially eaten by Pallas's fish eagles (Haliaeetus leucoryphus), Egyptian (Neophron percnopterus) and red-headed vultures (Sarcogyps calvus). The Indian wintering eagles do not appear to shun hunting terrestrial creatures and have been seen to hunting also snakes, rodents and other small mammals in the region.[5][29][123]

A drongo mobs a wintering greater spotted eagles, which are predators of birds of various sizes.

Ancedotal evidence of the diet of wintering greater spotted eagles was attained in the central plains of Thailand. Here they were seen to eat dead fish in drained ponds as well as to actively hunt and to pirate food from other raptors. They were seen to prey on domestic ducks (Anas platyrhynchos domesticus) that became separated from their large farm flocks as well as to feed on dead lesser whistling ducks (Dendrocygna javanica) found to be killed by poisons meant to kill off snails.[80] One farther prey species reported to be likely highly important to this region’s greater spotted eagles is the ricefield rat (Rattus argentiventer).[4][29] Despite not being an eagle considered to show an aptitude for attacking large or varied prey, sometimes greater spotted eagles seem to be capable of taking very varied and sometimes substantially sized prey.[5][9][108] It has been detected that small invertebrates may be taken at times, including ground beetles, locusts and non-native red swamp crayfish (Procambarus clarkii).[110][115] The greater spotted eagle takes a range of birds ranging down to the size of the 18.4 g (0.65 oz) common reed bunting (Emberiza schoeniclus). They can take fairly large water birds up to the size of grey herons, mallards, fledgling painted storks (Mycteria leucocephala), Asian openbills and greater white-fronted geese (Anser albifrons) as well as some cormorants and flamingoes. Most such water bird prey may weigh somewhere between 1,200 and 3,000 g (2.6 and 6.6 lb).[5][28][110][115][124] Sometimes the greater spotted eagle will attack or feed on cranes, although they not infrequently scavenge these as well. Many attacks attempted against cranes are reportedly unsuccessful against these tough prey. Likely cases of predation on adult common cranes (Grus grus) have been reported while one a demoiselle crane (Grus virgo) was unsuccessful while they were considered a potential threat possibly to the young of red-crowned cranes (Grus japonica). In some cases, they may taking cranes weighing up to some 5,000 g (11 lb).[110][125][126] Outside of avian prey, less varied prey is known to be taken of other taxa, though mammals have been taken ranging from Eurasian harvest mouse (Micromys minutus) and common shrew (Sorex araneus), weighing no more than 8 g (0.28 oz) up to the size of a nearly grown European hare (Lepus europaeus), potentially weighing up to 3,000 g (6.6 lb). Sometimes greater spotted eagles may prey upon around a half dozen species of mustelid mostly assorted weasels and stoats but also including larger species such as minks and martens.[108][110][127][128]

Interspecific predatory relationships

Greater spotted eagles such as this wintering in India often forage alongside and compete against sympatric eagle species.

Greater spotted eagles often overlap broadly with a number of similar eagle species in both its breeding and wintering haunts.[4][24] Although they are most obviously similar in dietary biology to the lesser spotted eagles, in the larger portion of their breeding range, the greater spotted eagles are allopatric from the lesser spotted.[41] Where they do overlap, the greater spotted eagle has a somewhat similar diet to that of the lesser spotted eagles but tends to focus more so water-friendly species and to take relatively more birds, whereas the lesser spotted eagle often focuses variously on voles, small snakes such as grass snakes and frogs.[129] Expectedly from its prey, the lesser spotted eagle tends to nest in slightly drier environments, usually somewhat away from wetlands and floodplains, adapting rather more readily to patchwork areas where human development has occurred.[8][85][130] More similar in central distribution are larger eagles such as the eastern imperial eagle and steppe eagle.[4][7]

Furthermore, these species undertake roughly similar migratory routes, though the steppe is clearly the most populous and regular migrant (in spite of its extreme decline), appearing in numbers from Africa to South Asia, while the greater spotted and eastern imperial eagles are regular to as far west as the Middle East and appear scarcely to rarely in Africa.[131][132][133] The greater spotted eagles is clearly partitioned, however, from the other eagles in its favoring of wet and partial wooded habitats and liking for animals that dwell in them as prey. The eastern imperial eagle also nests in woods but usually in rather upland areas and favors both social and solitary terrestrial mammals and birds, including hares, hamsters, ground squirrels and hedgehogs as well as pheasants, corvids and other mid-sized birds.[134][135] Meanwhile, the steppe eagle favours typically rather dry and very open habitats in the steppe, usually nesting on a rise or outcrop in the flat, sparse habitat, and much favours ground squirrels, supplemented by other rather small terrestrial species such as pikas, voles and zokors.[136][137] Usually habitat keeps these eagles rather separated from the greater spotted eagle while nesting, however in some winter quarters such as India, the Mediterranean Basin and the Middle East, considerable convergence occurs.[5][119][124][138]

All three eagles are well established to be rather unpicky opportunists and scavengers during winter, freely coming to human refuse, though favoring livestock carcass dumps, scavenging unclaimed carrion, robbing other birds of prey of their catches, killing the young of prey such as water birds, finding insect swarms or emergences (though more so the steppe than the others) and following grass fires. Of these three, the steppe tends to be least actively predatory in winter typically, the imperial the most likely to continue to live-hunt (and perch most extensively) and the greater spotted eagle somewhere in the intermediate behavioral zone. The greater spotted is the least likely of the three to visit carrion or carcass dumps but in the Indian subcontinent, they all heavily share food sources such as nestling water birds.[4][5][119][120] When conflicts arise, the body size of eagle imparts its position in the hierarchy, with the eastern imperial eagle dominant, followed by the steppe eagle while the greater spotted eagle is somewhat subservient to both. The three eagles were well studied in Bharatpur, where they competed against the shorter distance migrant, the Pallas's fish eagle, which vied with the imperial eagles for the dominant raptor position while all the larger eagles dominated the smaller competing resident Indian spotted eagles.[120] A non-eagle raptor often associated with wintering greater spotted eagles, attracted to similar feeding opportunities, is the black kite (Milvus migrans).[139]

A greater spotted eagle in Israel.

While scavenging, the greater spotted eagles tend not to come to carrion if Old World vultures are present.[5] The greater spotted eagles is an accomplished pirate during the winter season. They often rob a variety of other raptors including black kites (Milvus migrans), ospreys (Pandion haliaetus), western (Circus aeruginosus) and eastern marsh harriers (Circus spilonotus) and even other eagles including larger species like white-bellied sea eagles (Haliaeetus leucogaster) and steppe eagles. Despite their typically inferior position to them, the greater spotted eagle was observed to often successfully displaced the steppe eagle in Bharatpur from disputed food, with the steppes being more tractable when gorged. They tend to rob the other raptor aerially when the victim is trying to take initial flight with the prey, taking advantage of the other bird’s attempt to balance itself, during which they yank away the prey and escape fairly rapidly.[5][80][119][123][140]

More infrequently, greater spotted eagles will exploit other raptors as prey. Some species they been known to prey have including black kites, booted eagles (Hieraeetus pennatus), western marsh harriers and common buzzards (Buteo buteo) as well as some owls like long-eared (Asio otus) and short-eared owls (Asio flammeus). Additionally, they were considered a potential predator of small nestlings of the Eurasian griffon (Gyps fulvus).[5][110][115][141] The greater spotted eagles themselves have few well documented predators.[7] While this is probably due in part to scant research, usually as a quite large and powerful bird of prey, it usually fulfills the role of an apex predator.[24][127] However, one well documented predator of likely any aged greater spotted eagles is the Eurasian eagle owl (Bubo bubo).[142][143] Furthermore, European pine martens are known to feed on nestlings of greater spotted eagles.[108]

Often the greater spotted eagle occurs in pairs or solitary, but in winter sometimes occurs in small to large flocks, especially around attractive food source.[4] The species is often seen singly seen in migration, though sometimes in twos or threes or more.[4]

The display of this eagle on territory is not well known but includes single or mutual high circling, soaring high and the male diving down on half-closed wings towards the female, all with much calling.[4] Territories can be from 15 to 30 km² (5.8 to 11.6 sq mi) in ideal regions, usually within the confines of a protected area, though are much larger elsewhere.[29]

In the past, it has been reported that greater spotted eagle nests have been found as close as 100 m (330 ft) from each other and in one case 4 pairs nested in an area of merely 0.6 km² (0.23 sq mi), a more typical range may be in the zone of 40 to 52 km² (15 to 20 sq mi).[7] The density of greater spotted eagles was 4.76 (per confirmed numbers) to 6.15 (per projections based on available habitat) breeding pairs per 100 km² (39 sq mi) of forested area in the Volga-Ural region while in the Western Siberia region, it was 6.55 to 8.76 breeding pairs in the metric estimates on 100 km² (39 sq mi).[6] The highest density though was in Volga-Ural area, with up to 3.58-17.01 pairs where the locally preferred habitat (flooded alders) was available. The mean distance between nests in the Volga-Ural area was 7.3 km² (2.8 sq mi).[6] In the Ishim River basin of Kazakhstan there are about 0.54 pairs per 100 km² (39 sq mi), while in the Kazakh Irtysh pine forests there was a density of 1.08 pairs per 100 km² (39 sq mi) in internal edges of pine forests and a much higher density of 13.23 pairs per 100 km² (39 sq mi) of edges of forests along lakes and bogs in the Irtysh basin.

However, the possible highest density of pairs in Kazakhstan is possibly the region of the Ishim River, holding perhaps 39% of the nation’s breeding pairs.[144] Based on wintering greater spotted eagles in Spain, a wintertime territory may be similar or slightly smaller, at around 27.2 km² (10.5 sq mi).[145] Furthermore, in well suited Russian habitats, nests were said (at least historically) to be found every 1.6 km (0.99 mi) of riverside, with fairly consistent pair reuse in following years.[7] This species breeds from late April to August in much of its range.[4] However, when breeding in Pakistan and elsewhere in the Indian subcontinent, they may do so in different reports from November to March, sometimes further into June to July, indicating an inconsistent nesting schedule there.[4][5]

Development of young

Egg, Collection Museum Wiesbaden

In Russia, they reportedly seldom lay eggs until May, but sometimes as early as late April, with similar if mildly earlier laying times farther west.[7][29] The clutch size is typically two though sometimes the nest contains one to three eggs.[4][7] The eggs are broad ovals that are grayish white in colour and tend to be glossless and often unmarked. However, sometimes they may manifest a few dark brown spots or blotches and sparse grey shell-marks.[7]

The eggs may range in height from 63 to 74 mm (2.5 to 2.9 in), with an average of 67.5 mm (2.66 in) in one sample and 68.9 mm (2.71 in) in another, by 47.8 to 56.7 mm (1.88 to 2.23 in) in diameter, with an average of 54 mm (2.1 in) and 54.4 mm (2.14 in).[6][7][149]

The incubation stage lasts 42–44 days per most sources, but in southern Belarus, an incubation stage of only 39 days was documented.[4][150] Incubation begins with the first egg.[7] The male of the pair was once thought to not to take part in incubation (typically, as in many raptors, they primarily have the responsibility of prey deliveries).[7] However, in the aforementioned Belarusian study, the male incubated an average of 57.3 minutes during daylight.[150]

In the Altai taiga region, among 6 greater spotted eagle territories, the average brood size was 1.33 nestling per successful nest or 1.0 nestling per occupied nest. Two of the Altai greater spotted eagle territories were on the abandoned territories of eastern imperial eagles.[151] Meanwhile, in the Volga-Ural and Western Siberia areas, the mean brood sizes were 1.24 and 1.42, respectively.[6]

The body size between the greater spotted eagle nestlings differs markedly when the second eaglet hatches and the younger usually dies, often via siblicide.[7] Competition often resulting in starvation or intentional killing of the younger chick by its elder sibling is not uncommon in birds of prey, especially the eagles, and is often hypothesized as a kind of insurance process wherein the younger sibling acts an insurance if the elder sibling is somehow killed, otherwise the younger sibling (which is not necessarily in ill health) is possibly expected to die.[152][153] However, this species raises two fledglings at least somewhat more commonly than the lesser spotted eagle.[7][154] Out of 50 nests in the Oka Nature Reserve, though, only one pair managed to produce two fledglings in a year.[155]

In an experiment in a nest in Poland, a younger sibling was taken out of the nest to save it, with the younger eaglet weighing 310 g (11 oz) against 1,050 g (2.31 lb) for the older sibling at the point of extraction. After being taken out of the nest, the younger eaglet was raised with minimal interactions, to avoid imprinting, beyond feeding in captivity by humans. The eaglet shared a cage with an eastern imperial eagle and a lesser spotted eagle both of which were indifferent towards and did not in any way care for or feed the young greater spotted eagle. At the point of fledgling the young eagle was successfully reintroduced to its own parent's nest, fledged and attained independence.[155]

The mother greater spotted eagle can be a somewhat tight sitter but can abandon the nest when disturbed by humans, in a Belarusian study for a full day before returning.[7][150] By late July to early August, the young are fully feathered, soon takes its first flight in not more than 5 days.[7] Fledgling is at 60–67 days, averaging close to 62 days.[4] In Altai-Sayan region, the mean number of fledglings per successful nest could vary from a mean of 1 per nest in Tuva to 1.8 in Khakassia.[118] In Kazakh studies, a mean of 1.38 fledglings were produced in 11 nests.[144] In Western Siberia, a mean of 1.44 fledglings were produced in 66 broods.[156]

Further dependence on the parents lasts to 30 days more after fledgling.[4] Before dispersing for good, the young greater spotted eagles may wander locally into the open steppe for a little while.[7] Female greater spotted eagles were found to leave 2–3 days before their young in a study in Poland,. Meanwhile, the male tends to leave leave last, at about 1 week after the female. In the Polish study, adults headed straight for Bosphorus while juveniles were sometimes less direct.[157] Most were gone from Poland by the end of September, juveniles also seen to wander in elsewhere in Poland during autumn before finally migrating.[157]

Wintering greater spotted eagle in Israel.

Despite maintaining a fairly vast breeding range, covering at least 9 million square kilometres, in a band from the Baltic Sea in Europe right across to the Pacific Ocean with minor outpost in the Indian subcontinent, this eagle occurs at extremely low densities.[4]

The populations and trends of the species have been considered fairly poorly studied in the past, but a strong declining trend has been detected.[4][29] Rough estimates in the 1990s indicated some 11 pairs in a huge area of northeastern Poland, around 2,000 km² (770 sq mi) and only some 20-30 pairs in a huge study area of 85,000 km² (33,000 sq mi) in European Russia, with no more than 900 pairs west of the Urals.[4] More refined subsequent efforts put the number of breeding pairs in the European Union at 810 to 1100 breeding pairs.[19]

Furthermore, in the 1990s, it was extrapolated from Indian wintering populations that the more eastern population is surely less than four figures.[4] Birdlife International in the 1990s estimated the Russian population at 2800-3000 pairs. More recently, Birdlife has estimated the global population as no more than 3800-13,200 total mature individuals worldwide.[1][4][29]

Color-banding recovery studies have determined that of 1370 European band recoveries of spotted eagles, only 3.6% were greater spotted eagles, while hybrid greater x lesser spotted eagles comprised 2.7%, the remaining numbering being all lesser spotted eagles.[164] Greater spotted eagles are considered extripated as a breeding species from Hungary, Romania, Bulgaria, Czech Republic (where they may have never consistently bred) and Slovakia, as well as Israel where they last bred in the 1960s. Meanwhile, the Finland breeding population is also likely almost gone.[4][29][19]

Steady reduction in Ukraine down to 40-50 pairs by 1985 and a 12-20% overall reduction of the Ukrainian population was estimated, from 1920s to 1990s.[4][165] The numbers of greater spotted eagles in Estonia declined 14% in the period merely from 2004 to 2010, with declines having been detected for some time there.[11][166] The number of breeding pairs in Belarus is as many 150-200 pairs (with confirmed counts of somewhat over 100 breeding pairs) and this is considered the most important breeding area known outside of Russia.[19]

Where the total numbers in European Russia were once estimated at around 1000 breeding pairs in the 1960s, it is estimated that there are fewer than 700 pairs left there.[29][167] The range has shrunk in the Russian Far East, where it once widely found but is now restricted to below the middle Amur, along the Ussuri and south Primorsky although anecdotal information suggests that it is still somewhat common in the whole Western Siberian lowlands from the Ural Mountains to the middle Ob River.[29] In Kazakhstan, there are an estimated 74-97 breeding pairs of the species.[144]

Wintering estimates are more scattered and efforts to tabulate numbers in India show they continue to occur quite broadly but in perhaps slightly lowered and more scattered numbers.[5][168][169][170] In Armenia, it is considered one of the two rarest of the nation’s 30 raptor species, along with the eastern imperial eagle.[171] Wintering numbers of greater spotted eagles in the Mediterranean Basin were found to total about 300-400 individuals, with a bit under 34% of these in Israel, just under 32% in Greece, 16% in Turkey, somewhat smaller numbers in Romania and Spain and tiny numbers in Southeastern Europe, Montenegro and France.[66] Around 50 individuals winter in Turkey per other sources.[88]

The species appears fairly rarely in Ethiopia and Eretria where they are seen singly and sparsely in most cases.[71] In essentially every nation of its distribution, the greater spotted eagle has a Vulnerable status.[19] As a species, the greater spotted eagle is classified as vulnerable to extinction by the IUCN.[1]

Threats and conservation efforts

A couple of greater spotted eagles wintering in India.

The primary threats are habit degradation and habitat loss.[1][29] Greater spotted eagles appear to be highly sensitive to habitat alterations, especially drainage of wetlands, intensified agricultural practices and abandonment of floodplain management practices.[85][172]

Detrimental wetland management processes have additionally effected the species on their wintering grounds, where in Saudi Arabia at least, the effect has been offset by the greater spotted eagles adapting to man-made bodies of water (unlike in winter, though, there is no evidence that they adapt well to man-made areas during breeding).[173][174] The amount of usable manmade habitats has shrunk in Thailand with a change to dry season rice field cropping and the creeping presence of urbanization, along with probable rodenticide usage and other poisonings, likely harming numbers of the species able to winter there.[80]

Other threats are known to include human disturbance during the mating season, with forestry operations known now to be a major cause of disturbance at the nest site.[29][172] Furthermore, greater spotted eagles are threatened by mostly inadvertent poisonings and collisions with man-made objects, especially electrical wires.[4][175] Poisonings were known to be a serious cause of mortality in Shanxi reserve of China where the eagles were seen to hunt down sickly or dying common pheasants (Phasianus colchicus) that had been poisoned and then subsequently dying themselves, this becoming the primary local source of mortality.[29][176]

In the Malay Peninsula, subsequent to a brief increase of the species from the 1960s to the 1980s due to environmental changes favorable to avian scavengers, a crash in numbers down to almost none there was thought to be quite likely due to pesticide and other poison usage.[19][82] The real trends of greater spotted eagles are sometimes masked by misidentifications.[4]

Furthermore, as aforementioned, the species is at threat of hybridization and ultimate supplanting by the lesser spotted eagle as that species’ range creeps farther east.[3][10] The greater spotted eagle is legally protected in a scattered amount of nations, making conservation efforts difficult.[1][29] Among the nations where they are legally protected are Belarus, Estonia, France, Greece, Latvia, Poland, Romania, Russia and nominally in Thailand. A working group specifically to address spotted eagles has been established as of the 21st century.[1][29][177] The working groups have managed to undertake conservation efforts in Belarus, Estonia and the Ukraine, among the core breeding areas left in Europe for the species and they’ve successfully instituted restrictions of forestry activities near the nest sites during the breeding season.[1][29][177]

The building of artificial nest platforms did not seem to greatly aid greater spotted eagles in Nizhny Novgorod, unlike other raptors such as the osprey, the white-tailed eagle (Haliaeetus albicilla) and the golden eagle, as only one pair of greater spotted eagles were recorded to use a platform as a nest and higher survey numbers of greater spotted eagles in that region were likely only due to more extensive surveying.[146][178] In an exceptional positive note, it was found the European population of greater spotted eagle, as studied via microsatellites, retains quite high genetic diversity, meaning that there is no eminent threat of a genetic bottleneck for the species.[3][179][180]

Wikimedia Commons has media related to Clanga clanga.

Wikispecies has information related to Clanga clanga.

• Greater spotted eagle Photographs, text and map at Oiseaux.net
• BirdLife species factsheet for Clanga clanga
• "Clanga clanga". Avibase.
• "Greater spotted eagle media". Internet Bird Collection.
• Greater spotted eagle photo gallery at VIREO (Drexel University)
• Audio recordings of Greater spotted eagle on Xeno-canto.