Breeding birds are found only in Spain, circa 150 pairs. The range includes the Sierras of Guadarrama and Gredos, the plains of the Tajo and Tiétar rivers, the central hills of Extremadura, Montes de Toledo, Alcudia valley, Sierra Morena and the Guadalquivir marshes (Doñana). In addition there are occasional nesting reports from Salamanca and Málaga.
During the last century the range was considerably reduced. In Morocco it has disappeared as a breeding species, although one pair was found recently (1992) and juveniles are regularly reported, some of them ringed as chicks in Doñana National Park. In Portugal it is now very rare, with occasional observations, but no breeding has been recorded in recent years.
In Spain it was a relatively common raptor at the beginning of this century, with a range extending over most of the country where habitat was available (except the Cantabrian mountains and the Pyrenees). The population has declined drastically over the last 80 years, birds having disappeared from central and southern Portugal, northern and eastern Spain and the Penibetic Sierras. It was close to extinction in the 1960s when only 30 pairs were found. Recovery started in the early 1980s at a rate of five new breeding pairs per year up to 1994. The breeding population is monitored annually in the main protected areas which include Thirty-three percent of the breeding territories. The main breeding populations are in Monfragüe Natural Park (Cáceres), Doñana National Park (Huelva) and "Monte del Pardo" (Madrid). The estimated population size has increased annually in Spain since 2000, and the species has recently recolonised Portugal (two pairs). Some of these increases can be attributed to more thorough searches within its range (notably in Andalucía), which is currently split into three subpopulations with relatively little interchange

Spanish Imperial Eagles are found in three types of landscape: alluvial plains and dunes in the Guadalquivir marshes, plains and hills in central Spain and high mountain slopes in the Sistema Central. Except for four pairs that have used electricity pylons, nesting is in trees, with up to 16 tree species known to have been used, most frequently cork oak Quercus suber and stone pine Pinus pinea. The average distance between nests of different pairs is 6.5 km and the average density is one pair per 52 km². The highest density is in Doñana and the lowest in the Tajo valley; breeding density in protected areas is four times greater than in unprotected areas.
The abundance and distribution of rabbits are two of the main factors influencing population density, range and reproductive performance, while a low incidence or absence of irrigated farmland is the best predictor of the eagle's presence. Nests tend to be located in zones with abrupt relief, far from roads, tracks, towns and powerlines and where access is difficult. However, newly settled and subadult pairs show greater tolerance of human presence. The Spanish Imperial Eagle prefers areas with a Mediterranean climate, relatively hot, dry summers and warm, rainy winters. The breeding territories are regularly dispersed which indicates that neither food resources nor nest-sites are limiting.

The Spanish Imperial Eagle nests in trees, normally pine Pinus or oak Quercus. Most clutches are laid between 21 February and 20 March, the earliest date recorded being 15 February and the latest 28 April. The average clutch is 2.47, two eggs being most common. Hatching success is 71.7%, with 1.36 chicks fledging per occupied nest and 1.7 fledging per successful nest. Of the total number of birds that attempt to breed, 80% breed successfully. Numbers of rabbits Oryctolagus cuniculus and the age of the paired birds are the factors that most affect breeding success. Success is greater in areas with more rabbits, and in adult pairs compared with subadults. The degree of human activity and influence in the nesting territories and the associated disturbance may, in some way, affect breeding performance. A decrease in breeding success has been noted with increasing proximity to roads and people.
Cainism (aggression between siblings) is common in Spanish Imperial Eagles and frequently leads to the death of the youngest chick. The young fledge at 65-78 days old and remain 3-6 weeks in a small area near the nest, dependent on their parents to provide food. Parental negligence and aggression determine the move to independence and the start of juvenile dispersal. Once independent, the juveniles leave the area in which they were reared and make ever-greater dispersal movements.

Rabbits generally make up half the prey items and in some cases as many as 70%. Other prey worth mentioning are hares Lepus, pigeons, partridges, Corvidae, reptiles and ungulate carrion of both domestic and wild species. In Doñana the most important prey items, apart from rabbits, are aquatic birds (wildfowl, coots Fulica, herons, egrets and waders).

This species has been downlisted to Vulnerable because recent information shows that what was previously believed to be a population decline was in fact a brief levelling out of an overall upward trend. Although immature birds continue to suffer from unnaturally high mortality rates caused by poisoning, electrocution and insufficient food availability, reproductive success and fledging rates are high and have increased in recent years, allowing it to gradually reoccupy many areas within its former distributional range. The population remains very small, however.

Adults sedentary. Young birds, when they become independent, leave natal areas, dispersing in all directions and travelling up to 350 km, especially to NW Africa. During dispersal the young tend to concentrate in a few specific localities with an extraordinary abundance of rabbits, moving between the various sites. These focal areas, which are very important for the survival of the species, are located in the south-west of Madrid, the Tiétar valley (Toledo), south-east of La Mancha (Ciudad Real), south-west of Badajoz, the Guadalquivir marshes (Huelva) and El Andévalo and Medina-La Janda plains (Cádiz).

article number 1 Title
Long-term changes in nest defense intensity of the spanish Imperial Eagle Aquila adalberti.
Author(s): Ferrer M., Garcia L. & Cadenas R
Abstract: This paper deals with the variations recorded in the nest defence of the Imperial Eagle Aquila adalberti after the declaration of Donana as a national park (Parque Nacional Donana, SW Spain) and the c..[more]..
Source: ARDEA 78 (3): 395-398.
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