Eastern Imperial Eagle Profile
Until recently, there was one species of eagle described as having a range from Western Portugal all the way to Central Asia.
Known as the Imperial eagle, researchers apparently ignored the fact that those in Portugal were a different colour, different size, behaved differently and were quite evidently a different animal than those found all the way over in the Far East.
Fortunately, someone insisted, and now there are two distinct species. The Spanish Imperial eagle, found – you guessed it! – in Spain, Portugal and the Iberian Peninsula, and this one: the Eastern Imperial Eagle.
Eastern Imperial Eagle Facts Overview
| Habitat: | Tall wooded areas with clearings |
| Location: | Southeast Europe, West and Central Asia |
| Lifespan: | 44 years in captivity |
| Size: | Up to 90cm (35 in) long, 2.2m (7 ft 3 in) wingspan |
| Weight: | Around 3.2 kg (3.8 lb) |
| Colour: | Tawny brown, mottled |
| Diet: | Small mammals, reptiles birds, carrion |
| Predators: | None |
| Top Speed: | Unknown |
| No. of Species: | 1 |
| Conservation Status: | Vulnerable (IUCN) |
Eastern Imperial Eagles have a wide range of relatively low-density and have survived well as a species with their impressively diverse set of feeding strategies that they can adapt where needed.
This has not prevented their decline due to deforestation, but there is a lot of promise for their protection if conservation efforts can be extended.
Interesting Eastern Imperial Eagle Facts
1. They’re not the Spanish Imperial Eagle
While they’re both in the same genus, it wasn’t until 2002 that mitochondrial assessments of the two species gave researchers enough confidence to suggest the Spanish and the Eastern Imperial eagles are different species.
The two were already considered subspecies of the Eastern Imperial eagle, Aquila heliacal but have been geographically, and therefore genetically, isolated for long enough for a speciation event to occur.
This isolation happened around the end of the Ice Age, and since then, the two species have diverged significantly.
2. They’ll eat just about anything
The Eastern Imperial eagle has a far greater range, and like its sister species, is a mid-sized, generalist and opportunistic predator.
It not only has a diverse menu, but a varied repertoire of hunting strategies to match. Most of its prey is taken on the ground, some from the water surface, and occasionally, it will take fledgelings from nests in trees.
They’ll also chase down small animals like insects and worms and will take ground squirrels on foot by waiting outside their burrows in ambush.
This species also steals kills from other predators and sometimes teams up to hunt in pairs.
With all these skills in its arsenal, it’s unsurprising that the diet of this species consists of up to 300 different species of animal, making them impressively generalistic. Still, hares and rodents are the preferred prey for most populations, with reptiles, birds, fish and invertebrates filling in the gaps. 1
3. But different populations specialise in different prey items
This range of behaviours and preferences isn’t all seen within a single population but spread out across various subpopulations across the eagle’s range.
While there is versatility within each population, they tend to pick preferences based on food availability, and different groups of eagles will employ different feeding strategies as a result.
Diet diversity can range from highly specialised in times of food scarcity to far more diverse where possible, and the latter was associated with better breeding success. Population density also increases dietary diversity, likely as a result of intra-specific competition.
In Slovakia, the Imperial eagle’s nesting behaviour has been affected by a reduction in ground squirrels and hamsters and have adapted their hunting strategies more toward pigeons. In Hungary, this same drop in squirrels has led eagle populations to increase the amount of hamsters and [European hare] in their diets. 2 3
4. They’re woodland specialists
Nesting occurs almost exclusively in trees, with a few on cliff faces or otherwise inaccessible rocky outcrops. Preferred trees are between 40-70 years old, meaning the eagles have evolved to live and breed in mature woodland and forest.
They prefer to nest on high and will use the same nest for up to five years. Sometimes they’ll have a second, holiday nest, that they maybe maintain as a backup, as this is often a previously used nest that they’re reluctant to give up on entirely.
This species will choose wooded areas with clearings, from which they can effectively hunt their food within the nesting and roosting territories.
5. They exhibit reverse sexual dimorphism
“Reverse Sexual Dimorphism” is a silly term and you should side-eye anyone who uses it.
Sexual dimorphism is the phenomenon in which a species exhibits dramatic morphological (shape, colour or size) differences between the two sexes.
In humans, men are typically taller, hairier, and more likely to wear chequered shirts than women, but this isn’t the case in all animals. Female angler fish are notoriously fond of tartan and can be hundreds of times bigger than the male.
This is sexual dimorphism too, but because the male is smaller, it’s come to be referred to as “reverse sexual dimorphism” which shamelessly exposes a bias towards humans and males as the norm, and the basis for comparison.
And this isn’t a good starting point, as in most sexually dimorphic species the female is larger, so if anything were to be considered the ‘reverse’, it would be the human examples.
Regardless, In Eastern Imperial eagles, females are roughly 10% larger than males, which is pretty much the norm in raptors. 4
6. They’re long-distance birds
Another big difference between this species and the Spanish Imperial eagle is the habit of migration. Eastern Imperials move around a lot more than their Flamenco dancing cousins, both within the season and between over-wintering sites.
Long-distance trips take them as far afield as Mongolia for the Winter, and there’s an element of vagrancy among the species too, in which animals just sort of move around with no clear intention. Some have been tracked travelling from Russia to Arabia and back, with some moving as far as 5,000km in a single Spring trip.
Some small populations have even been found as far South as Tanzania. Other populations prefer balut to injera, and so will overwinter in Cambodia or Laos.
7. They’re threatened by logging
Deforestation is something we often associate with Africa, South America and Asia, and that’s because humans have already removed more than half of Europe’s native tree cover and forgotten what it used to be like. But there are forests left in Europe, and they’re being destroyed at a worrying rate.
Breeding sites across this eagle’s range are threatened by deforestation, especially in Russia. Illegal logging removes viable reproductive areas for the species, and new-growth forest just doesn’t have the same vibe to them, providing fewer tall trees to nest in and mature ecosystems to hunt in.
Central Europe is developing fast, and by 2016, it was estimated that the eagle had lost 30% of its potential habitats in Hungary.
Powerlines are killing birds all over the world, and large raptors like this are particularly susceptible. 450 Eastern Imperial Eagles were killed in the 2009 breeding season in the Altai region alone, representing a quarter of the population there.
Predator poisoning is also on the rise in areas with increased livestock presence, and all of these factors reduce the species’ ability to compete with others such as the Greater spotted eagle.
8. Sustained conservation efforts do help
But conservation is showing some positive results already. Since 2000, the Bulgarian population has demonstrated its ability to bounce back in the presence of systemic conservation efforts. Many territories showed population increases and several territories were re-occupied by the species.
Productivity increased across the board, and the species re-entered the Czech Republic to become a new breeding species, and in 2010, this population jumped up in number.
Secure nesting sites, tracking, ringing and supplementary feeding are all thought to have contributed to this recovery and should be considered across the species range as part of an overall conservation strategy. 5
Eastern Imperial Eagle Fact-File Summary
Scientific Classification
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Accipitriformes |
| Family: | Accipitridae |
| Genus: | Aquila |
| Species: | Heliaca |
Fact Sources & References
- Márton Molnár (2022), “Eastern Imperial Eagle – Aquila heliaca”, YouTube.
- Jozef Chavko (2012), “Raptor Journal”, sciendo.
- TODD E. KATZNER (2005), “Relationship between demographics and diet specificity of Imperial Eagles Aquila heliaca in Kazakhstan”, Wiley Online Library.
- John P. Swaddle (2000), “A novel evolutionary pattern of reversed sexual dimorphism in fairy wrens: implications for sexual selection”, Oxford Academic.
- David Horal (2011), “Eastern Imperial Eagle (Aquila heliaca) in the Czech Republic”, Research Gate.