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
Eagle is the common name for the golden eagle, bald eagle, and other birds of prey in the family of the Accipitridae. Eagles belong to several groups of Genus, genera, some of which are closely related. True eagles comprise the genus ''Aquila ( ...
native to the
Iberian Peninsula
The Iberian Peninsula ( ), also known as Iberia, is a peninsula in south-western Europe. Mostly separated from the rest of the European landmass by the Pyrenees, it includes the territories of peninsular Spain and Continental Portugal, comprisin ...
. The
binomial
Binomial may refer to:
In mathematics
*Binomial (polynomial), a polynomial with two terms
*Binomial coefficient, numbers appearing in the expansions of powers of binomials
*Binomial QMF, a perfect-reconstruction orthogonal wavelet decomposition
* ...
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
In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...
of the
eastern imperial eagle
The eastern imperial eagle (''Aquila heliaca'') is a large bird of prey that breeds in southeastern Europe and extensively through West and Central Asia. Most populations are migratory and winter in northeastern Africa, the Middle East and South a ...
, but is now widely recognised as a separate species due to differences in
morphology
Morphology, from the Greek and meaning "study of shape", may refer to:
Disciplines
*Morphology (archaeology), study of the shapes or forms of artifacts
*Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...
,
ecology
Ecology () is the natural science of the relationships among living organisms and their Natural environment, environment. Ecology considers organisms at the individual, population, community (ecology), community, ecosystem, and biosphere lev ...
,
[ and molecular characteristics.
]
Description
This is a large raptor and quite large eagle, broadly similar in size to its cousin, the eastern imperial eagle
The eastern imperial eagle (''Aquila heliaca'') is a large bird of prey that breeds in southeastern Europe and extensively through West and Central Asia. Most populations are migratory and winter in northeastern Africa, the Middle East and South a ...
, which is found in a considerably different distributional range. Compared to sympatric largish booted eagles, it is somewhat smaller than the golden eagle
The golden eagle (''Aquila chrysaetos'') is a bird of prey living in the Northern Hemisphere. It is the most widely distributed species of eagle. Like all eagles, it belongs to the family Accipitridae. They are one of the best-known bird of pr ...
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
The wedge-tailed eagle (''Aquila audax'') also known as the eaglehawk, is the largest bird of prey in the continent of Australia. It is also found in southern New Guinea to the north and is distributed as far south as the state of Tasmania. A ...
as the third heaviest member of the '' Aquila'' genus behind the golden and Verreaux's eagle
Verreaux's eagle (''Aquila verreauxii'') is a large, mostly African, bird of prey. It is also called the black eagle, especially in southern Africa, not to be confused with the black eagle (''Ictinaetus malayensis'') of south and southeast Asia. ...
s. This species has a total length of and a wingspan of .[European Raptor Conservation European This is a national bird of ]Spain
Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...
Spanish Imperial Eagle, Aquila adalberti.
'' Accessed 17 May 2011 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.[Ferguson, L. J., & Christie, D. A. (2001). ''Raptors of the World''. London (UK): Christopher Helm.]
Distribution and habitat
The species occurs in central and south-west Spain
Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...
and adjacent areas of Portugal
Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...
, in the Iberian Peninsula
The Iberian Peninsula ( ), also known as Iberia, is a peninsula in south-western Europe. Mostly separated from the rest of the European landmass by the Pyrenees, it includes the territories of peninsular Spain and Continental Portugal, comprisin ...
. Its stronghold is in the dehesa woodlands of central and south-west Spain, such as in Extremadura
Extremadura ( ; ; ; ; Fala language, Fala: ''Extremaúra'') is a landlocked autonomous communities in Spain, autonomous community of Spain. Its capital city is Mérida, Spain, Mérida, and its largest city is Badajoz. Located in the central- ...
, Ciudad Real
Ciudad Real (, ) is a municipality of Spain located in the autonomous community of Castile–La Mancha, capital of the province of Ciudad Real. It is the 5th most populated municipality in the region.
It was founded as Villa Real in 1255 as a ro ...
and areas in the north of Huelva
Huelva ( , , ) is a municipality of Spain and the capital of the Huelva (province), province of Huelva, in the Autonomous communities of Spain, autonomous community of Andalusia. Located in the southwest of the Iberian Peninsula, it sits betwee ...
and Seville's Sierra Norte. The Spanish imperial eagle is a resident species, unlike the partially migratory eastern imperial eagle.[ Stable occurrence in ]Morocco
Morocco, officially the Kingdom of Morocco, is a country in the Maghreb region of North Africa. It has coastlines on the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to Algeria–Morocc ...
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.[Las águilas imperiales vuelven a Marruecos y mueren electrocutadas, Ciencia, EL PAÍS](_blank)
/ref> Vagrant birds have even reached Mauritania
Mauritania, officially the Islamic Republic of Mauritania, is a sovereign country in Maghreb, Northwest Africa. It is bordered by the Atlantic Ocean to the west, Western Sahara to Mauritania–Western Sahara border, the north and northwest, ...
and Senegal
Senegal, officially the Republic of Senegal, is the westernmost country in West Africa, situated on the Atlantic Ocean coastline. It borders Mauritania to Mauritania–Senegal border, the north, Mali to Mali–Senegal border, the east, Guinea t ...
. North of its natural range, vagrants have reached as far as the Netherlands
, Terminology of the Low Countries, informally Holland, is a country in Northwestern Europe, with Caribbean Netherlands, overseas territories in the Caribbean. It is the largest of the four constituent countries of the Kingdom of the Nether ...
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
''Quercus suber'', commonly called the cork oak, is a medium-sized, evergreen oak tree in the section ''Quercus'' sect. ''Cerris''. It is the primary source of cork for wine bottle stoppers and other uses, such as cork flooring and as the core ...
'') 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
Siblicide (attributed by behavioural ecologist Doug Mock to Barbara M. Braun) is the killing of an infant individual by its close relatives (full or half siblings). It may occur directly between siblings or be mediated by the parents, and is dr ...
. 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.[
]
Food and feeding
The Spanish imperial eagle feeds mainly on European rabbit
The European rabbit (''Oryctolagus cuniculus'') or coney is a species of rabbit native to the Iberian Peninsula (Spain, Portugal and Andorra) and southwestern France. It is the only extant species in the genus ''Oryctolagus''. The European rab ...
s, which comprised about 58% of this species' diet before myxomatosis
Myxomatosis is a disease caused by '' Myxoma virus'', a poxvirus in the genus '' Leporipoxvirus''. The natural hosts are tapeti (''Sylvilagus brasiliensis'') in South and Central America, and brush rabbits (''Sylvilagus bachmani'') in North ...
and rabbit haemorrhagic disease
Rabbit hemorrhagic disease (RHD), also known as viral hemorrhagic disease (VHD), is a highly infectious and lethal form of viral hepatitis that affects European rabbits. Some viral strains also affect hares and cottontail rabbits. Mortality rate ...
greatly reduced the rabbit's native Iberian population. As rabbit population crashed they have been recorded feeding on a wide range of vertebrate
Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain.
The vertebrates make up the subphylum Vertebra ...
s with varied success depending upon prey populations and may become semi-specialized hunters of water bird
A water bird, alternatively waterbird or aquatic bird, is a bird that lives on or around water. In some definitions, the term ''water bird'' is especially applied to birds in freshwater ecosystems, although others make no distinction from seabi ...
s especially Eurasian coot
The Eurasian coot (''Fulica atra''), also known as the common coot, or Australian coot, is a member of the rail and crake bird family, the Rallidae. It is found in Europe, Asia, Australia, New Zealand and parts of North Africa. It has a slaty-bla ...
s, duck
Duck is the common name for numerous species of waterfowl in the family (biology), family Anatidae. Ducks are generally smaller and shorter-necked than swans and goose, geese, which are members of the same family. Divided among several subfam ...
s and geese
A goose (: geese) is a bird of any of several waterfowl species in the family Anatidae. This group comprises the genera '' Anser'' (grey geese and white geese) and ''Branta'' (black geese). Some members of the Tadorninae subfamily (e.g., Egyp ...
, also taking some numbers of partridge
A partridge is a medium-sized Galliformes, galliform bird in any of several genera, with a wide Indigenous (ecology), native distribution throughout parts of Europe, Asia and Africa. Several species have been introduced to the Americas. They ar ...
s, pigeon
Columbidae is a bird family consisting of doves and pigeons. It is the only family in the order Columbiformes. These are stout-bodied birds with small heads, relatively short necks and slender bills that in some species feature fleshy ceres. ...
s and crow
A crow is a bird of the genus ''Corvus'', or more broadly, a synonym for all of ''Corvus''. The word "crow" is used as part of the common name of many species. The related term "raven" is not linked scientifically to any certain trait but is rathe ...
s and any other bird they happen to encounter that is vulnerable to ambush. More than 60 bird species are known in be included in their prey spectrum. Several mammals may also be taken including various rodent
Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...
s, hare
Hares and jackrabbits are mammals belonging to the genus ''Lepus''. They are herbivores and live Solitary animal, solitarily or in pairs. They nest in slight depressions called forms, and their young are precociality, able to fend for themselves ...
s, mustelid
The Mustelidae (; from Latin , weasel) are a diverse family of carnivoran mammals, including weasels, badgers, otters, polecats, martens, grisons, and wolverines. Otherwise known as mustelids (), they form the largest family in the suborde ...
s, hedgehog
A hedgehog is a spiny mammal of the subfamily Erinaceinae, in the eulipotyphlan family Erinaceidae. There are 17 species of hedgehog in five genera found throughout parts of Europe, Asia, and Africa, and in New Zealand by introduction. The ...
s and even other large predators such as red fox
The red fox (''Vulpes vulpes'') is the largest of the true foxes and one of the most widely distributed members of the order Carnivora, being present across the entire Northern Hemisphere including most of North America, Europe and Asia, plus ...
es or—rarely, since they are not typically present in the eagle's habitat—domestic cats and small dogs. Rarely, reptiles or even fish may also be preyed upon. The largest prey taken by this species may easily exceed , such as foxes, greylag geese or white stork
The white stork (''Ciconia ciconia'') is a large bird in the stork family, Ciconiidae. Its plumage is mainly white, with black on the bird's wings. Adults have long red legs and long pointed red beaks, and measure on average from beak tip to en ...
s, but mean prey mass is relatively low, especially in areas with fewer rabbits. One study reported mean prey mass as locally, though a larger average prey size has also been reported.[González, L. M. (2016). ''Águila imperial ibérica – Aquila adalberti''. En: ''Enciclopedia Virtual de los Vertebrados Españoles''. Salvador, A., Morales, M. B. (Eds.). Museo Nacional de Ciencias Naturales, Madrid.]
The Spanish imperial eagle is one of several rabbit-favoring birds of prey in Spain along with the similarly specialized Iberian lynx
The Iberian lynx (''Lynx pardinus'') is one of the four wikt:extant, extant species within ''Lynx'', a genus of medium-sized wild Felidae, cats. The Iberian lynx is endemic to the Iberian Peninsula in southwestern Europe. It is listed as vulnera ...
. This species is largely segregated by habitat from other eagles that specialize on rabbits here to lessen direct competition, as the imperial eagle favors woods, whereas the golden and Bonelli's eagles tend to dwell in much rockier areas. However, Spanish imperial eagles frequently quarrel over food with various raptors, even much larger vultures
A vulture is a bird of prey that scavenges on carrion. There are 23 extant species of vulture (including condors). Old World vultures include 16 living species native to Europe, Africa, and Asia; New World vultures are restricted to North and ...
, and the raptors may at times try to kill the young of one another. In one case, in protection their own nest, an adult Spanish imperial eagle even killed a cinereous vulture
The cinereous vulture (''Aegypius monachus''), also known as the black vulture, Eurasian black vulture, and monk vulture, is a very large Raptor (bird), raptor in the family Accipitridae distributed through much of temperate Eurasia. With a body ...
, the largest accipitrid in the world. Healthy, free-flying Spanish imperial eagles are apex predator
An apex predator, also known as a top predator or superpredator, is a predator at the top of a food chain, without natural predators of its own.
Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the hig ...
s, being mostly free of natural predators themselves but they do sometimes kill each other in conflicts and rarely interspecies conflicts may too be fatal. When protected from human persecution and far from threats such as powerlines, adult mortality can be as low as 3–5.4% annually.[
]
Conservation
The species is classified as Vulnerable by the International Union for Conservation of Nature
The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the stat ...
. Threats include loss of habitat
Habitat destruction (also termed habitat loss or habitat reduction) occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved elsewhere, or are dead, leading to a decrease ...
, human encroachment, collisions with pylons (at some point in the early 1980s, powerlines were responsible for 80% of deaths among birds in their first year of life) and illegal poisoning. There has also been a decline in the species' main prey: rabbits have been kept at bay or even declined in some of the areas where the eagle is or could be present as a result of myxomatosis
Myxomatosis is a disease caused by '' Myxoma virus'', a poxvirus in the genus '' Leporipoxvirus''. The natural hosts are tapeti (''Sylvilagus brasiliensis'') in South and Central America, and brush rabbits (''Sylvilagus bachmani'') in North ...
and, most recently, rabbit haemorrhagic disease
Rabbit hemorrhagic disease (RHD), also known as viral hemorrhagic disease (VHD), is a highly infectious and lethal form of viral hepatitis that affects European rabbits. Some viral strains also affect hares and cottontail rabbits. Mortality rate ...
.
By the 1960s it had become a critically endangered
An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...
species, with only 30 pairs remaining, all located in Spain. Following conservation efforts, recovery began in the 1980s at a rate of five new breeding pairs per year up to 1994. Imperial eagles were nearly wiped out. In 2011, the species's global population had increased to 324 pairs, with 318 pairs in Spain. The species recolonised Portugal in 2003, after an absence of breeding activity for over 20 years, and has been slowly increasing since, with six breeding pairs located in 2011 and nine located in 2012. The population in Spain showed an average annual increase of around 7% between 1990 and 2011. These positive trends are largely attributed to mitigation measures to reduce mortality associated with powerlines, supplementary feeding, reparation of nests, reintroductions and decreases in the disturbance of breeding birds, although some of the observed increases may be due to more thorough searches within its range.
References
Sources
*
*
* Ferguson-Lees, James & Christie, David A. (2001): ''Raptors of the World''. Houghton Mifflin, Boston. .
* Ferrer, Miguel (2001): ''The Spanish Imperial Eagle''. Lynx Edicions
Lynx Nature Books, based in Barcelona, is a publishing company specializing in ornithology and natural history. The company was founded in 1989. It was formerly named Lynx Edicions.
History
Lynx Nature Books was founded as Lynx Edicions in Barce ...
, Barcelona. .
*
*
*
External links
BirdLife Species Factsheet
{{Authority control
Spanish imperial eagle
Birds of Southern Europe
Fauna of the Iberian Peninsula
Birds of North Africa
Spanish imperial eagle
Eagles
Spanish imperial eagle