Imperial Eagle | Aquila heliaca

Voice

Silent away from the nest, but in the territory clearly noisier than most eagles. From a high branch or in display it gives a deep, barking ok-ok-ok-ok or rowk-rowk, loud and far-carrying, far fuller than the thin yelping of a Golden Eagle; when excited it speeds up into a rolling kokokoko. Loudest from March to May; young beg in July with a hoarse, persistent call.

Identification

Large and heavily built, with long, broad wings with straight leading and trailing edges held flat in a soar, or at most a trace above the horizontal; the wing does not narrow at the base. The head and long neck project clearly forward and the tail is fairly long and square-ended. The outer six primaries are deeply fingered; the exact number of fingers changes with moult and says less than the shape of the hand, which looks long and squarely cut off. The adult is blackish brown with a pale ochre to golden crown and hindneck running from the forehead well down the neck, and with small, separate white spots on the scapulars — usually one to three, sometimes hardly visible and never a continuous band. The tail is grey with a broad black terminal band. First-year birds are sandy ochre with heavy dark streaking on breast and mantle, two narrow pale bars across the wing coverts, a pale wedge on the inner primaries and a pale rump patch; the flight silhouette is then two-toned, a pale body against dark flight feathers.

Confusion species

Golden Eagle soars in a distinct shallow V, has wings pinched at the base, a longer tail slightly rounded at the tip and a head that projects less; its golden nape is confined to the hindcrown, whereas the Imperial has the whole crown and neck pale. Juveniles differ most clearly: young Golden Eagle shows sharply defined white patches at the base of the primaries and a white tail base with a broad black terminal band, while young Imperial shows a pale wedge on the inner primaries, two narrow pale wing bars, a streaked breast and no white in the tail base. Spanish Imperial Eagle is separated by the white: in that species a clean white band runs along the leading edge of the inner wing right out to the bend of the wing and the crown is creamy white, while the Eastern bird has only separate spots and an ochre nape; the juveniles differ even more, that of the Spanish bird being plain rufous and unstreaked. Steppe Eagle lacks any white on the shoulder, has a yellow gape line running back beyond the eye, often carries the hand slightly drooped, and in immature plumage shows one broad, clean white bar across the wing coverts instead of two narrow ones. Greater and Lesser Spotted Eagles are smaller, with narrower wings held bowed downwards in a glide. Naming works well for first-year birds and for full adults; between the second and fourth year the plumage is an irregular mixture of streaked juvenile and dark adult feathers, the white scapular spots only come through around the fourth or fifth year, and some of those birds have to be left unnamed in the field.

Habitat

Open lowland and hill country with scattered tall trees: steppe and puszta, cereal and lucerne fields, pasture and rough field margins, and along the edges of deciduous woodland and shelterbelts. It builds a big nest high in a poplar, oak or elm, often at a wood edge or in a solitary tree out in the arable, and hunts over the surrounding open fields. Main prey are susliks, hamsters, hares, pheasants and crows, supplemented with carrion in winter.

Range and movements

From the Pannonian basin across the Balkans to Anatolia, the Caucasus and the steppes of eastern Europe, and on eastwards into Central Asia, so only part of the range falls inside the map area. The Pannonian basin is the stronghold; elsewhere in central Europe and the Balkans numbers are smaller but growing. Adults stay near the nest all year, while young birds move to the Middle East and north-east Africa. In north-western Europe it is an extreme rarity, involving wandering immatures, and every claim needs careful documentation. It is absent from Iberia, where only the Spanish Imperial Eagle breeds.

• Resident
• Breeding (summer)
• Winter
• Passage
• dark = core range, pale = thinly spread

How and when to look

The best bets are the Hortobágy, the Kiskunság and above all the loess hills at the foot of the Bükk and Zemplén ranges, in April and May between nine and twelve, as the first thermals build and pairs circle over their territory. Drive the field tracks, stop at a high point overlooking arable with scattered trees, and scan the tree tops and the pylons; a perched Imperial Eagle stands out at long range by its pale head. The Sakar hills and the plains around Iğdır work well too.

Conservation status

Vulnerable on the IUCN Red List. The European population is growing thanks to nest guarding, the insulation of dangerous pylons and the investigation of poisoning cases, but it remains small and fragile. Illegal poisoning with banned agricultural chemicals in baits is the leading cause of death in central Europe, followed by electrocution on medium-voltage poles, shooting along the migration route, felling of nest trees and collisions with wind turbines. The collapse of suslik colonies as grassland is ploughed up also makes the food supply uncertain.

Scientific name

Aquila heliaca | de Savigny, 1809

De Savigny described the species in 1809 and placed it straight away in the genus where it still stands. The genus Aquila was introduced in 1760 by Brisson. Aquila is Latin for 'eagle', possibly from aquilus 'dark in colour'. heliaca is Greek for 'of the sun', from hēlios 'sun'. The specimen the first description was based on came from Upper Egypt.