The Spanish imperial eagle (Aquila adalberti), also known as the Iberian imperial eagle, the Spanish eagle or Adalbert's eagle, is a species of eagle native to the Iberian Peninsula. The binomial commemorates Prince Adalbert of Bavaria. Due to its distinct "epaulettes", old literature often referred to this species as the white-shouldered eagle.
Formerly, the Iberian imperial eagle was considered to be a subspecies of the eastern imperial eagle, but is now widely recognised as a separate species due to differences in morphology, ecology, and molecular characteristics.
Description
This is a large raptor and quite large eagle, broadly similar in size to its cousin, the eastern imperial eagle, which is found in a considerably different distributional range. Compared to sympatric largish booted eagles, it is somewhat smaller than the golden eagle and somewhat larger than the Bonelli's eagle. Spanish imperial eagle can weigh from . The average weight of males in a sample of 10 was while that of 17 females was found to be . Meanwhile, another sample of 10 unsexed adults weighed an average of . Thus, the Spanish imperial eagle weighs about 10% more on average than the eastern imperial eagle and rivals the considerably longer-winged and longer-tailed wedge-tailed eagle as the third heaviest member of the Aquila genus behind the golden and Verreaux's eagles. This species has a total length of and a wingspan of . A typical wingspan for a male is reportedly about while for a female may be about .
The adult resembles the eastern imperial eagle and can superficially suggest the golden eagle (especially when distantly seen), but is overall a darker color than either, a rich blackish-brown which extends all the way from the throat down to the belly. Like the eastern imperial, the adult has a broad distinctive white band on the shoulder and leading edge of the wing, which is even more pronounced in the Spanish than in the eastern species, and a much paler tawny color on the nape and crown, unlike the golden-yellow color on a similar area in the golden eagle. The juvenile Spanish imperial eagle is very different from adults and other large raptors in this range, being overall a uniform pale straw-sandy colour, contrasting with broad black bands on both the upper and lower sides of the wings. It has a relatively longer neck, and generally much flatter wing profile in flight than the upturned dihedral typical of a golden eagle.
Distribution and habitat
The species occurs in central and south-west Spain and adjacent areas of Portugal, in the Iberian peninsula. Its stronghold is in the dehesa woodlands of central and south-west Spain, such as in Extremadura, Ciudad Real and areas in the north of Huelva and Seville's Sierra Norte. The Spanish imperial eagle is a resident species, unlike the partially migratory eastern imperial eagle. Stable occurrence in Morocco is disputed but immature birds during the dispersion period regularly visit Morocco.
Rising numbers of vagrant birds born in Spain and then electrocuted in Morocco have been noted; some areas used by the species in Morocco could be becoming sort of a "drain" in terms of the species recovery and this is due to the fact that the country stands in a similar situation as Spain was in the early 1980s when it comes to insulation of transmission towers. Vagrant birds have even reached Mauritania and Senegal. North of its natural range, vagrants have reached as far as the Netherlands in one rare occasion.
Behaviour and ecology
Breeding
Nesting habitat is usually dry, mature woodlands, which they utilize for nesting and seclusion, but nests are most often fairly close to shrubby openings and wetland areas where prey is more likely to be concentrated. A shy species toward man, they normally nest only where human disturbance is quite low. Like most raptors, they are highly territorial and tend to maintain a stable home range. Spanish imperial eagles nest from February to April. The nesting pair will construct a nest of as much as across when first built, which will increase in time, especially in mature cork oaks (Quercus suber) or pine trees. Clutch size is usually two to three eggs, with an incubation period of about 43 days, but on average about 1.23-1.4 fledglings are produced per nest. Nestling mortality is usually due to human disturbance and destruction and nest collapses, secondarily due to predation and siblicide. Fledging is reached at 63–77 days of age but juveniles can linger for an extremely long period, to at least 160 days after fledging.