Eastern Imperial Eagle

The eastern imperial eagle (Aquila heliaca) is a large bird of prey that breeds in southeastern Europe and extensively through West and Central Asia. Most populations are migratory and winter in northeastern Africa, the Middle East and South and East Asia. Like all eagles, the eastern imperial eagle is a member of the family Accipitridae. Furthermore, its feathered legs mark it as a member of the subfamily Aquilinae. It is a large, dark-colored eagle, with a resemblance to other members of the genus Aquila, but it is usually the darkest species in its range. It is an opportunistic predator that mostly selects smallish mammals as prey but also a fairly large proportion of birds, reptile an...

The eastern imperial eagle is distributed as a breeding species largely along the southern edge of the vast taiga forests. The habitat preferred by the species is often rather open country with scattered trees or more enclosed woodlands, as well as around or near wetlands. The imperial eagle often forages mainly in open areas, extending to beyond typical assorted grasslands to wetlands and agricultural areas. In more extensive wooded areas, eastern imperial eagles require glades or meadows in order to executive hunting. The central part of their range as a breeding species occurs in vast areas of steppe and here the species often inhabits forest-steppe mosaics, as well as woodland edges, riparian zones and agricultural lands with trees or wooded patches. Lowland areas tend to be preferred, albeit not exclusively. In Turkestan and Kazakhstan, they may extend their breeding habitat into semi-desert. True desert is used during winter so long as foods are available. Largely where golden eagles are absent, the species has been reported to range into secondary habitats such as forested lower mountains and montane steppe and meadowland. In Europe at least, this is due to human pressures, which caused them to abandon open lowlands, timbered plains and river-fringed forests for forested, precipitous uplands. A slow repopulation of their preferred lowlands reported since the 1990s in Slovakia and Hungary. Often, eastern imperial eagles winter in more open habitats such as nearly continuous grassland, plains, semi-desert and cultivation with scattered trees as well as various marshes, lakes and other wetlands. The species resides mainly from sea level to 1,300 m (4,300 ft), locally to 1,800 m (5,900 ft), and has been recorded on passage at 3,900 m (12,800 ft) in Asia.

India

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. 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.

The eastern imperial eagle is a fairly solitary bird, with rarely more than a pair occurring, although some small gatherings recorded at waterholes or food during migrant or winter. Pairs on the breeding grounds engage in aerial displays with loud calling and extensive high circling, which like most of accipitrids is likely for the purposes territorial proclamation to other eagles of their species. The display is often interspersed with mock dives and talon showing. One or both members of a pair may participate in the aerial display. If an interloper does not leave during the first part of the display, the territorial skirmish then may become physical and it sometimes leads to cartwheeling with interlocked talons, falling until they nearly hit the ground. Despite the fairly impressive display, it is generally of slightly shorter duration than the similar one done by golden eagles. In East Thrace, Turkey, the mean nearest nest distance between actively breeding pairs was 10.44 km (6.49 mi). In the Irkutsk Oblast near Lake Baikal, the mean distance of the central area of nests (each pair had more than one nest on territory) was 17 km (11 mi). The breeding season lasts from late March to September throughout the range but in their former range in Pakistan (where it is now extirpated as a breeder) was said to extend from November to April. The pair constructs a very large nest of sticks, which may average up to 1.2 to 1.5 m (3 ft 11 in to 4 ft 11 in) across and 60 to 70 cm (24 to 28 in) in depth. However, nests for the species have been recorded to measure up to 2.4 m (7 ft 10 in) or more across and 1.8 to 2 m (5 ft 11 in to 6 ft 7 in) deep. Nests can outmatch in size those even of larger species such as golden eagles. Nests are frequently lined with various materials, including twigs, grass, fur, debris and greenery. Usually eastern imperial eagles build their nest in tall trees but recorded down to as low as 2 m (6.6 ft) in low scrub or, rarely, on cliff or ground (later as recorded in the Sayan Mountains of Kazakhstan). Nest sites have been found anywhere from in the depth of a forest to forest edge to a solitary tree that may be visible for miles in open plains. Nesting sites in both Turkey and Georgia were consistently under 450 m (1,480 ft) elevation. In Georgia, denser mixed forests with openings were favored alternately with more arid, isolated stands of juniper (Juniperus ssp.) and pistachio (Pistacia vera); in Turkey, poplar (Populus ssp.) (44%) and oak (Quercus ssp.) (40%) were favored. In extensive Russian studies, 78% of nests were in conifers when compared with Kazakhstan where deciduous trees are more prevalent, however in the latter country conifers are still used where they are found. Unusual nest sites in agricultural land of Slovakia include one next to a railroad and another next to a busy road. The eastern imperial eagle has also been recorded as nesting on electric poles and towers in Russia and Kazakhstan. In several cases they aggressively took over the nests from steppe eagles that were previously nesting on the electric towers. Often one nest is used but sometimes a 2nd or 3rd is constructed by the imperial eagle pair may exist on a home range. The mother eastern imperial eagle lays 2 to 3 eggs at intervals of 2 or more days. The average clutch size in Georgia was 2.09. In the Czech Republic, the average clutch size was 2.27. 81 nests from Russia had a mean clutch size of 2.1. Exceptional clutch sizes of up to four eggs have been recorded in Kazakhstan. The eggs are a dull buffish white colour overall and are sparsely marked with grey, purplish or, occasionally, brown spots. A sample of 150 eggs were found to have measured from 63 to 82.5 mm (2.48 to 3.25 in) in height by 52.5 to 62.5 mm (2.07 to 2.46 in), with an average of 73.3 mm × 56.5 mm (2.89 in × 2.22 in). In Georgia, the average dimensions of eggs was measured in a sample of 20 as 72.3 mm × 57.5 mm (2.85 in × 2.26 in) with a mean weight of 136.8…

The eastern imperial eagle is a member of the Aquilinae or booted eagles, a rather monophyletic subfamily of the accipitrid family. At least 38 species are currently housed in the subfamily, all with signature well-feathered tarsi. This species is a member of the genus Aquila, which are mostly large, fairly dark colored eagles distributed largely through the more open habitats of Eurasia and Africa (with one in North America and a couple in Australasia). Studies on DNA have indicated that the imperial eagle is part of a subgroup with other moderately sized Aquila such as the steppe eagle (Aquila nipalensis) and the tawny eagle (Aquila rapax). Despite the outward resemblance to the imperial eagle, the 4 species in the golden eagle subgroup appear to be rather more closely related to the dissimilarly smallish and pale-bellied sister species, African hawk eagle (Aquila spilogaster) and Bonelli's eagle (Aquila fasicata). The Spanish imperial eagle, which is found in Spain and Portugal, was formerly lumped with this species, the name imperial eagle having been previously used in both circumstances. However, the two are now regarded as separate species due to significant differences in morphology, ecology and molecular characteristics. It is likely that the eastern imperial eagle is the paraspecies for the Spanish imperial eagle and that the imperial eagle complex reached the Iberian peninsula sometimes between the late Pleistocene era and early Holocene. The Spanish imperial eagle may be considered an ice age relict due to its isolation. The eastern imperial eagle is a large eagle, but usually falls near the average size of the large-bodied genus Aquila. Adult total length can range from 68 to 90 cm (27 to 35 in) with a typical wingspan of 1.76 to 2.2 m (5 ft 9 in to 7 ft 3 in). The average wingspan of a small sample showed males to average 1.95 m (6 ft 5 in) while a small sample of females averaged 2.07 m (6 ft 9 in). Although otherwise outwardly similar, the species displays 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. In terms of body mass, one survey found five males to weigh from 2.45 to 2.72 kg (5.4 to 6.0 lb) and five females to weigh from 3.26 to 4.54 kg (7.2 to 10.0 lb). The average weight of this sample of imperial eagles was reportedly 2.62 kg (5.8 lb) in the males and 3.9 kg (8.6 lb) in the females. A sample of unknown size showed males to weigh an average 2.88 kg (6.3 lb) while females reportedly weighed an average of 3.38 kg (7.5 lb). A further two mature females weighed an average of 3.56 kg (7.8 lb). Among standard measurements, males may range in wing chord length from 540 to 622 mm (21.3 to 24.5 in), in tail length from 260 to 308 mm (10.2 to 12.1 in) and in tarsus length from 91 to 98 mm (3.6 to 3.9 in). Meanwhile, females may range in wing chord length from 565 to 665 mm (22.2 to 26.2 in), in tail length from 270 to 330 mm (11 to 13 in) and in tarsus length from 97 to 107 mm (3.8 to 4.2 in). A sample of imperial eagles ranged in total bill length from 65.7 to 76.5 mm (2.59 to 3.01 in). 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. 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 brac…

The eastern imperial eagle is a powerful bird of prey but frequently overlaps in range with multiple other eagle species and that may require them to share both habitats and prey. The golden eagle is generally a larger, more powerful bird. It also tends to be a bolder, more aggressive predator than the imperial eagle and may be able to attack much larger prey. While the mean prey body mass relative to the eagle's weight is probably similar between the two species, an estimated 15% of golden eagle prey will weigh over 5 kg (11 lb). In its very extensive range, the golden eagle's distribution includes nearly all areas occupied by breeding eastern imperial eagles. Furthermore, there is considerable overlap in prey species selected by these species. There is a natural partitioning between the two Aquila species and that comes in the form of habitat preferences. The golden eagle takes to, usually but not always, rocky and uneven terrain, so favors mountainous areas with alpine meadows to access for prey. This is quite different from the eastern imperial eagle's preference for a flat or somewhat rolling interface between wood stands and fields at low elevations. However, in some areas, especially eastern Europe, eastern imperial eagles have been driven to higher elevations and more montane habitats that are typically the haunts of golden eagles by persecution, habitat destruction, and other interferences by humans, usually with mixed to minor success as the golden species is scarce at best locally and unlikely to produce competition. There is surprisingly little information on conflicts between these two eagle species. In the Naurzum Nature Reserve of Kazakhstan the golden and eastern imperial eagle, and to some extent also both white-tailed eagles and steppe eagles, were recorded nesting with fairly close proximity to each other. The eagle species here would even use nests built by the other species and seemed to have similar or broadly overlapping food habits, but no interspecies conflicts were detected. On the contrary, in the Altai Republic, it appears that golden and eastern imperial eagles are considered to fill a largely similar ecological niche in abutting areas and do compete for nesting sites. In some cases in Europe, golden and eastern imperial eagles will engage in a territorial display if prompted against one another. Of a similar distribution to eastern imperial eagles, both in their mid-Eurasian breeding ground and southerly Indo-African wintering grounds, are the steppe eagle and the greater spotted eagle. There is a fair amount of habitat partitioning between the three species, however, with the steppe eagle preferring flat, often almost treeless steppe while the greater spotted eagle prefers more densely wooded and wetter habitats generally than imperial eagles such as taiga bogs. Diet however can overlap considerably, especially with steppe eagles as both it and the imperial species are largely attracted to colonies of ground squirrels in Central Asia. While steppe eagles occur much more broadly in Africa during winter and a similarly narrow extent in the Indian subcontinent as eastern imperials, greater spotted eagles are similarly as rare as imperial eagles in Africa but spread farther in Asia than either the steppe or imperial species. In all three species, by winter they are attracted to more open habitats ranging from savanna to wetlands and even semi-desert. The ecology of wintering eastern imperials was studied at length in Bharatpur district of India in contrast to the steppe and greater spotted eagle as well as the resident Indian spotted eagle and shorter-distance migrant Pallas's fish eagle. It was found that the feeding opportunities sought were largely similar (nestling water birds were often favored) by all five eagle species and that a hierarchy was formed, though each species competed most regularly with others of their own species. The eastern imperial eagle was, by and large, dominant in corresp…

The eastern imperial eagle is a member of the Aquilinae or booted eagles, a rather monophyletic subfamily of the accipitrid family. At least 38 species are currently housed in the subfamily, all with signature well-feathered tarsi. This species is a member of the genus Aquila, which are mostly large, fairly dark colored eagles distributed largely through the more open habitats of Eurasia and Africa (with one in North America and a couple in Australasia). Studies on DNA have indicated that the imperial eagle is part of a subgroup with other moderately sized Aquila such as the steppe eagle (Aquila nipalensis) and the tawny eagle (Aquila rapax). Despite the outward resemblance to the imperial eagle, the 4 species in the golden eagle subgroup appear to be rather more closely related to the dissimilarly smallish and pale-bellied sister species, African hawk eagle (Aquila spilogaster) and Bonelli's eagle (Aquila fasicata). The Spanish imperial eagle, which is found in Spain and Portugal, was formerly lumped with this species, the name imperial eagle having been previously used in both circumstances. However, the two are now regarded as separate species due to significant differences in morphology, ecology and molecular characteristics. It is likely that the eastern imperial eagle is the paraspecies for the Spanish imperial eagle and that the imperial eagle complex reached the Iberian peninsula sometimes between the late Pleistocene era and early Holocene. The Spanish imperial eagle may be considered an ice age relict due to its isolation.