Greater Spotted Eagle

The greater spotted eagle (Clanga clanga), also called the spotted eagle, is a large migratory bird of prey in the family Accipitridae. It is a member of the subfamily Aquilinae, commonly known as "booted eagles". It was once classified as a member of the genus Aquila, but has been reclassified to the distinct genus Clanga, along with the two other species of spotted eagle. During breeding season, greater spotted eagles are widely distributed across Eastern Europe, parts of Central Europe, central Russia, central Asia and parts of China, along with other isolated areas. During winter, they migrate, primarily to South Asia, Southeast Asia, the Middle East, the upper Mediterranean Basin, an...

Greater spotted eagles are found in open wet forests and forest edges, often adjoining marshes, swampy patches, bogs, or wet meadows, as well as river-valley woodlands and floodplain forests. They are generally found in wetlands more often than lesser spotted eagles, but can be found in drier hillside forests in Central Asia. The difference in habitat preferences between these species was confirmed in northeastern Poland, where greater spotted eagles nested in wooded areas on floodplains with considerably more annual flooding than those nested in by lesser spotted eagles. Although typically scarce while breeding in areas modified by heavy human development, they have been seen hunting over cultivated land in Estonia and migrating over lowland farms in the Czech Republic. In Russia, they are found in transition zones between taiga forest and open steppe (often around river valleys), in pine forests, near dwarf forests, in wet, wooded areas of the steppe, and in forested swamps. In Kazakhstan, riparian forests in lowland steppes and forest-steppes mosaics are their primary habitat. In winter, much like during breeding, they usually occur in wetter habitats than most other eagles, including forested river deltas, mangrove forests, marshes, lakeshores, and, in India especially, jheels. However, greater spotted eagles have also been documented in semi-arid Acacia savannas in northeastern Africa. Reportedly in Eritrea, they occur in open moorland, around villages, and lowland grasslands, while in Sudan they are usually in shrubby areas. One seen wintering in Ankara, Turkey, was in an upland forest area. In the Mediterranean Basin, a study found that the preferred habitats of wintering greater spotted eagles were salt marshes and coastal lagoons with freshwater areas. They are not uncommon in paddy fields and sometimes garbage dumps in Asia during winter, being much more adaptable to human-modified areas in this season, though by and large prefer assorted wetlands, mudflats, large rivers, estuaries, and mangroves. In Arabia, they are largely found now in manmade habitats—such as sewage farms, reservoirs, and agricultural land—since the native mangrove and Phragmites reed-beds that once lined the coastal bays have been almost entirely eliminated. In southern Iran, they are usually found in mangrove areas. A key habitat in Iraq is the Mesopotamian Marshes. Wintering habitats in Israel are the wettest available valleys and damp open zones, chiefly cultivated fields and fishponds near patches of trees, with similar habitats used in Oman. Greater spotted eagles are typically found from sea level to 300 m (980 ft) and are characteristically a lowland bird. However, they have been recorded at elevations up to 4,000 m (13,000 ft) in northern Iran. One greater spotted eagle was recorded on migration at 4,370 m (14,340 ft) in Ladakh in the Himalayas.

Russia

The greater spotted eagle is a slightly opportunistic predator but tends to favor rather particular prey types. Their diet tends to be composed mostly of small mammals. Despite some dietary similarities with the lesser spotted eagle, the greater spotted eagle's diet includes more birds and favors larger prey. 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. Pellets are considered the most reliable way to determine the diets of greater spotted eagle, as prey remains alone can be biased towards birds. As can be expected by their habitat preferences, greater spotted eagles tend to eat vertebrates associated with water. Generally, its prey spectrum is somewhat diverse, at slightly fewer than 150 known prey species; this is more diverse than the known diet of the steppe eagle, similar in diversity to that of the lesser spotted eagle, and possibly about half as diverse of the diet of the eastern imperial eagle. Greater spotted eagles hunt mainly on the wing, quartering over relatively open ground (somewhat like a harrier) or soaring high above and dropping or diving steeply when prey is spotted. Brown and Amadon describe the hunting greater spotted eagle, saying: "Although not a very active species it is not exactly sluggish, and on the wing it has the look of a true eagle." Greater spotted eagles will scatter waterfowl by stooping low over their flock, then selecting isolated individuals to attack. 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 water. The species also sometime carries out kleptoparasitic attacks on other birds of prey. Although scavenging for carrion seems to occur almost aseasonally, it is likely more prevalent during non-breeding times, when the eagles mostly bring fresh prey to their nests. Along with other predators such as steppe eagles, greater spotted eagles are often attracted to grass fires and swarming locusts during non-breeding times. 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 by the male (the main food provider) may have been more varied than later in the season when the female resumed hunting. In Biebrza, hunting territories were defended from conspecifics, 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%. The hunting success rates of greater spotted eagles seem rather high—the aforementioned 34% for much of the breeding season is much higher than the hunting success rates of golden eagles (Aquila chrysaetos) (around 20%), lesser spotted eagles (24%), and Bonelli's eagles (Aquila fasciata) (28.5%) at comparable times. It is sometimes stated that they tend to take prey mostly up to only 250 g (8.8 oz). One source estimated that around 22% of prey constituting their diet weighs 63 g (2.2 oz) or less, 37% weighs 63–125 g (2.2–4.4 oz), and around 30% weighs 125–250 g (4.4–8.8 oz), and that generally most prey weighs 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). A large study from Belarus found that the diets of greater spotted eagles were predominantly composed of prey with body masses of 51–200 g (1.8–7.1 oz) (41.9%) and 11–50 g (0.39–1.76 oz) (38.3%). However, the greatest contributor to total prey biomass was from prey weighing 601–1,200 g (21.2–42.3 oz) (34%). In this study, the mean estimated size of prey deliveries by males was 161.2 g (5.69 oz). In contrast, an Estonian stu…

The greater spotted eagle is quite noisy when breeding and is often very vocal in winter, especially when in small loose flocks. The most common call, often heard during intraspecies conflicts, is a soft, one-syllable, penetrating, high-pitched, urgent whistle, variously transcribed as kyack, kluh, tyuck, or dyip. The call is not unlike that of lesser spotted eagles but is slightly deeper and more ringing. The calls are higher pitched than steppe eagles' and much higher pitched than those of the eastern imperial eagles (Aquila heliaca), the latter having a guttural call somewhat reminiscent of a frog. Additionally, a similar three-syllable bark is seemingly used to warn off intruders at a feeding site, sometimes considered a harsh chrr-chrr-chaa-chaa, kyak-yak-yak, and kyew-kyew-kyew. The cumulative effect of the repeated call has been compared to that of a "small hound". As with many raptors, the female's tone is lower pitched and hoarser. One individual greater spotted eagle recorded over two days was found to utter an unusual ringing call that sounded remarkably similar to the first two syllables of the typical call of the crested serpent eagle (Spilornis cheela).

Greater spotted eagles often occur in pairs or solitary, but in winter sometimes occur in small to large flocks, especially around attractive food sources. The species is often seen singly during migration, though sometimes in twos or threes or more. This species breeds from late April to August in much of its range. However, when breeding in Pakistan and 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. The display of this eagle is not well-known but includes single or mutual high circling, soaring high with the male diving down on half-closed wings towards the female, all with much calling. 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. In the past, greater spotted eagle nests have been reportedly found as close as 100 m (330 ft) from each other; in one case, four pairs nested in an area of merely 0.6 km2 (0.23 sq mi). A more typical range may be in the zone of 40–52 km2 (15–20 sq mi). 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 6.55–8.76 breeding pairs per 100 km2. The highest density was in the 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). In the Ishim River basin of Kazakhstan, there was 0.54 pairs per 100 km2. In the Kazakh Irtysh pine forests, there was 1.08 pairs per 100 km2 in internal forest edges, and a much higher density of 13.23 pairs per 100 km2 in forest edges along lakes and bogs in the Irtysh basin. The highest density of pairs in Kazakhstan is possibly the region of the Ishim River, holding perhaps 39% of the nation's breeding pairs. 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.

The greater spotted eagle is rather large and compact. Normally, it is black-brown with a contrasting yellow beak. This species has a short neck with a large and often shaggy-naped head, a 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. 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. 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 steep riverbank. 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 to blackish brown, though the coloration may appear purplish and glossy. They may appear more starkly contrasted when freshly moulted. The upperwing covert feathers 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 the latter is usually concealed at rest. The species is sexually dimorphic or even polymorphic. Pale and intermediate phenotypes are rare, although they can be slightly more common in eastern ranges. Pale adults, sometimes referred to as Clanga clanga fulvescens, have bicolored plumage. 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 coloring around the eyes, on the leading edges of wings, and more rarely and sparsely on the chest. 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. The juvenile greater spotted eagle is generally uniformly black-brown with whitish to yellowish drop-shaped spots. Some juveniles appear heavily spotted all over, while others are less so. They always show an obvious row of spots along the upperwing coverts, forming clear wing bars tail and flight feathers, except the outer primaries. Juveniles' feathers underneath 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 second to third year, the plumage is often considerably worn but white tips still create sufficiently prominent wing bars (unlike in lesser spotted eagles) until the second winter, when most coverts are then newly molted with smaller pale tips. From about the middle of third year onwards, the plumage is more adult-like with few or no indistinct spots left, but remiges are of unequal age and untidy looking. The subadult is generally more uniform in color, but often still shows some pale tips to the greater coverts. Maturity is obtained by about the fifth year, though sometimes they may not breed until the sixth. The bare parts change little in color at different ages, with eyes being dark brown, while the beak and feet are yellow in all ages. In flight, th…

At one time, greater and lesser spotted eagles may have been largely isolated from each other via different (though potentially proximal) habitats. Climate changes at the conclusion of the last ice age (at some point early in the Holocene) permitted forest growth where there were once grassy boundaries, allowing the two species of spotted eagles to expand into each other's ranges. Hybridization is now known to occur extensively. Hybrids occurs in the entire overlapping range of the two species, which is some 600,000 km2 (230,000 sq mi). Interbreeding is mostly determined via conjecture in European Russia, which is roughly the eastern limit of the lesser spotted eagle's range and thus where hybridization possibly occurred most recently. Hybrids between the two species often show a nape patch (absent in pure greater spotted eagles), an intermediate amount of spotting about the wings, and typically a larger body size than pure lesser spotted eagles. Despite their intermediate characteristics and larger size than lesser spotteds, the hybridization of the species is thought to be an indication of the abandonment of greater spotted eagle territories and the replacement of them by the more adaptive and populous lesser spotted eagles, as was indicated in an Estonian study. The Estonian study found that the number of pairs of hybrids in the nation was twice that of pure greater spotted eagles. The situation was even graver in Lithuania, where not a single pure pair of greater spotted eagles could be found any longer by the mid-2000s, with only 2.7% of 161 breeding spotted eagles being greater spotteds, the rest being lesser spotteds. Lesser spotted eagles were estimated to number around 1,000 breeding pairs in Lithuania, with an estimated 37 or so of these containing one mate that was a greater spotted eagle. Both Polish and Estonian studies reflected a probable high turnover of mates in hybrid pairs, with the Polish data finding about 71% of the males of the pairs being supplemented in subsequent years. Furthermore, the Polish data indicated that the hybrids favoured the habitats of lesser spotted eagles, farther away from the wetter habitats of the greater spotted eagle and often nearer human development, with a local 50% reduction of pure greater spotted eagle pairs and 30% increase in hybrid pairs. Habitat alterations to the environment by humans are thought in general to be partially beneficial to lesser spotted eagles and normally harmful to greater spotted eagles.

Despite maintaining a fairly vast breeding range—covering at least 9 million square kilometres in a band from the Baltic Sea in Europe eastward to the Pacific Ocean with minor outposts in the Indian subcontinent—this eagle occurs at extremely low densities. In essentially every nation of its distribution, the greater spotted eagle is classified as vulnerable to extinction by the IUCN. Populations and trends of the species have been considered rather poorly studied in the past, but a strong declining trend has been detected. Rough estimates in the 1990s indicated 11 pairs in a huge area of around 2,000 km2 (770 sq mi) in northeastern Poland, and only 20–30 pairs in an area of 85,000 km2 (33,000 sq mi) in European Russia, with no more than 900 pairs west of the Urals. More refined subsequent efforts put the number of breeding pairs in the European Union at 810–1,100 breeding pairs. Furthermore, in the 1990s, it was extrapolated from Indian wintering populations that the more eastern population is surely less than four figures. Birdlife International in the 1990s estimated the Russian population at 2,800–3,000 pairs. More recently, Birdlife has estimated the global population as no more than 3,800–13,200 total mature individuals worldwide. A color-banding recovery study determined that of 1,370 European banded recoveries of spotted eagles, only 3.6% were greater spotted eagles, while hybrids of lesser and greater spotteds comprised 2.7%, and the remaining were all lesser spotted eagles. 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. Steady reduction in Ukraine down to 40–50 pairs by 1985, and a 12–20% overall reduction of the Ukrainian population from the 1920s to 1990s, was estimated. The number of greater spotted eagles in Estonia declined 14% merely from 2004 to 2010, with declines having been detected for some time there. Belarus has as many as 150–200 breeding pairs (with confirmed counts of somewhat over 100) and is considered the most important breeding area known outside of Russia. Whereas the total numbers in European Russia were once estimated at around 1,000 breeding pairs in the 1960s, there are estimated to be fewer than 700 pairs remaining there. The species' range has shrunk in the Russian Far East, where it was once widely found but is now restricted to below the middle Amur river, along the Ussuri river, and south Primorsky Krai, 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. In Kazakhstan, there are an estimated 74–97 breeding pairs of the species. 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. In Armenia, it is considered one of the two rarest of the nation's 30 raptor species, along with the eastern imperial eagle. 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. Around 50 individuals winter in Turkey per other sources. The species appears fairly rarely in Ethiopia and Eritrea, where they are seen singly and sparsely in most cases.

Greater spotted eagles are members of the Aquilinae, or "booted eagles", subfamily, 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. Booted eagles are often grouped with the genera Buteo and Haliaeetus, and other more heavy-set Accipitridae, but they may be more closely related to the slenderer accipitrine hawks than previously believed. The greater spotted eagle's closest living relative is the lesser spotted eagle. They are believed to have diverged from their most recent common ancestor around the middle Pliocene, approximately 3.6 million years ago (mya). This "proto-spotted eagle" probably lived in the general region of modern-day Afghanistan, and split into northern and southern lineages when both glaciers and deserts advanced in Central Asia at the start of the last ice age. 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. Spotted eagles were classified as part of the genus Aquila, along with several other mostly large, brownish eagles. However, molecular phylogenetic studies using one mitochondrial and two nuclear gene sequences 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. 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. 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. The scientific name Clanga may derive from Ancient Greek κλαγγή (lit. 'scream'), or its root may be the Greek word klangos (a variant form of plangos) for "a kind of eagle" as mentioned by Aristotle. Extensive hybridization between the greater spotted eagle and the lesser spotted eagle occurs perhaps because the two species have one of the closest relationships of any closely studied Accipitrid taxa, despite significant genetic differences. 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. 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.