Until the 1980s both the Spanish imperial eagle and the Eastern imperial eagle were classified under the same taxon, Aquila heliaca. The result of genetic analyses determined a taxonomic separation into two different species: Heliaca Aquila for the Eastern species and Aquila adalberti for the Spanish species.

The colouring of the plumage varies with age, from the tawny colour of the young eagles, which becomes light ochre yellow on ageing, going through different designs where dark and light feathers overlap, to become the dark brown characteristic of the adults, with the typical white spots on the back of the neck and shoulders.

Biology
Imperial eagles are sedentary, territorial birds. The adult’s territory is divided into three areas: in the first it locates its nest, usually with an average extension of 1,500 ha, adjacent to this are the usual hunting grounds, with an average extension of 3,000 ha. These first two are defended actively from other eagles. Finally, there is another area, more remote, that may be shared with other eagles. Their diet is based fundamentally on rabbit, which may represent more than 50% of biomass consumed. This diet is completed by corvids, pigeon, other birds, reptiles and carrion. Imperial eagles begin courtship in the months of February-March. The number of eggs laid varies between 2 and 4 and the chicks are born from mid April to mid May, their first flight taking place at the end of July. Reproductive success (no. of chicks leaving the nest/no. of nests where at least one egg hatches) in Castilla-La Mancha during the period from 1989 to 2005 was 1.6 and productivity (no. of chicks in flight/no. of pairs that initiate reproduction) was 1.3 chicks/pair.

After independence, the young eagles begin a period of dispersal that induces them to move away from the areas of their birthplace. In this phase they usually settle down in areas with an abundance of food and after a fairly extensive period they tend to return to their native localities where they attempt to settle as breeders. This is a period of high mortality: a study done in the province of Toledo, using radio-surveillance of 41 juveniles radio-marked during the period 2001-2004, obtained a survival rate of 80% during the first year of life. The adult mortality rate, although somewhat lower, is high in Castilla-La Mancha: in the province of Toledo during the period 2001-2009 this was 8.5%, reaching 13% in 2009.

Habitat
The imperial eagle reaches its highest density in Mediterranean-type forest areas with a high density of rabbits and little human presence. Very frequently for nesting they choose relatively inaccessible big game estates, generally in mountainous areas, constructing large nest-building platforms on tree branches. In Castilla-La Mancha, as a result of a decrease in direct hunting, the species is beginning more often to occupy areas converted into pasture land, and plains with low hills; more inhabited areas, with major populations of rabbit. The species of trees they most often select for installing their nests in this region are the oak, the cork oak, and the Maritime pine, although up to 16 different species have been documented.

The areas of dispersal of the young adults are usually areas of plain, generally turned pasture land, or with little tree-cover, a high density of rabbits, and an absence of breeders.

Distribution
over the communities of Castilla-La Mancha, Castilla and Leon, Extremadura, Madrid and Andalusia. In Castilla-La Mancha their areas of reproduction are located in Montes de Toledo, Sierra Madrona-Sierra Morena Oriental, sierras de Almadén-Guadiana, the depression of the River Tagus, the valleys of the Rivers Tiétar and Alberche, and recently some locations in the province of Albacete. The most important areas of dispersal in the region are the valleys of the rivers Tagus and Tiétar in the province of Toledo, and the Campo de Montiel, between the provinces of Castilla-La Mancha and Albacete, where dispersing birds from their entire area of distribution may be seen.

Population
The world population of this species is around 200 pairs. In 2008 a total of 87 pairs were recorded in Castilla-La Mancha: 45 in Toledo, 40 in Castilla-La Mancha and 2 in Albacete. These numbers are a relative maximum for the species, since in the recent past the imperial eagle has suffered an alarming drop in numbers, reaching historic lows at the beginning of the 80s, when not more than 22-24 pairs were recorded. From then on a slow process of recovery began, not without difficulties, to reach the current situation. At this moment the general trend in centres of population in Castilla-La Mancha is increasing. Important to emphasise is the existence of breeding pairs in the province of Albacete since 2007. In contrast, in the valleys of the Tiétar and Alberche the species has not been able to recover from the lows mentioned in the 80s; quite the contrary, from the 5-6 pairs at that time we have now reached a worrying 2-3 pairs at present.

Growth in the number of breeding pairs of Spanish imperial eagle Turing the period 2004-2008 in Castilla-La Mancha (source Autonomous Organisation Espacios Naturales, Castilla-La Mancha)

Conservation
This bird of prey has suffered the destruction of large areas appropriate to it on Mediterranean hillside and scrubland. In addition, it also suffers from a high mortality rate caused by electrocution; the clandestine use of poisons, and poaching. The most important cause of death in young adults is electrocution, whereas breeding birds are worst affected by poison. Thus 78% of radio-tagged young adults found dead in Castilla-La Mancha were electrocuted. Furthermore, the huge drop in rabbit populations due to the introduction of diseases has greatly reduced the species’ possibilities of feeding. From 1993 and later, after the species conservation plan, a series of actions have been taken to conserve this bird of prey. These measures have consisted on the one hand of actions directed at increasing survival of the species and have consisted basically of isolating and modifying power lines to avoid electrocution, particularly in dispersal areas for young males, and the approval and application of the plan to fight against illegal use of poisons in the environment.

On the other hand, the other group of measures has been directed at increasing reproductive success by monitoring and protecting nests; sporadic, additional feeding of some pairs, reinforcing nest-building platforms at risk, and constructing artificial nests to decrease mortality of chicks in the nest due to collapse. In addition, work has been done to bolster rabbit populations and several sensitisation and education campaigns have been conducted, as well as those involving the private sector. All this has brought continuous recovery in the population and an increase in the area of distribution in Castilla-La Mancha, increasing success in reproduction and decreasing sub-adult and adult mortality.

Legal Status
Since 1990 the Spanish imperial Iberian, Aquila adalberti, has been included in the National Catalogue of Endangered Species (Royal Decree 439/1990. of 30th March) within the category “In Danger of Extinction”.

In Castilla-La Mancha, the species has been included in the Regional Catalogue of Endangered Species in the “In Danger of Extinction” category (Decree 33/1998 of 5th May). In September, 2003 the Recovery Plan for the Spanish imperial eagle was approved, through which areas critical to the survival of the species in this Community were declared as sensitive (Decree 275/2003, of 9th September.