The Spanish imperial eagle (''Aquila adalberti''), also known as the Spanish eagle or Adalbert's eagle, is a species of
eagle native to the
Iberian Peninsula. 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 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 ...
, 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, 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 ...
, 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 birds ...
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'') 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. Adults of this species have lo ...
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 Indian black eagle (''Ictinaetus malayensis''), which lives far to ...
s. This species has a total length of and a wingspan of .
[European Raptor Conservation European This is a national bird of Spain ]
Spanish Imperial Eagle, Aquila adalberti.
' Accessed 17 May 2011[Thiollay, J. M., Del Hoyo, J., Elliott, A., & Sargatal, J. (1994). ''Handbook of the Birds of the World, vol. 2., New World Vultures to Guineafowl''. Lynx Editions.][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.] 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. Smaller than the relatively small race of golden eagle found in the Iberian peninsula, it is somewhat slighter and slenderer in appearance compared to the more powerful golden species, with 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.]
Range
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
Extremadura (; ext, Estremaúra; pt, Estremadura; Fala language, Fala: ''Extremaúra'') is an autonomous communities in Spain, autonomous community of Spain. Its capital city is Mérida, Spain, Mérida, and its largest city is Badajoz. Loc ...
,
Ciudad Real
Ciudad Real (, ; en, "Royal City") 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.
History
It was founded ...
and areas in the north of
Huelva
Huelva (, ) is a city in southwestern Spain, the capital of the province of Huelva in the autonomous community of Andalusia. It is between two short rias though has an outlying spur including nature reserve on the Gulf of Cádiz coast. The rias ...
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.][Las águilas imperiales vuelven a Marruecos y mueren electrocutadas, Ciencia, EL PAÍS](_blank)
/ref> 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.
Ecology
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 at first build, which will increase in time, especially in mature ''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 cores ...
'' 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.[
It feeds mainly on European rabbits, 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 greatly reduced the rabbit's native Iberian population. As rabbit population crashed they've been recorded feeding on a wide range of vertebrates with varied success depending upon prey populations and may become semi-specialized hunters of water birds especially Eurasian coots, ducks and geese, also taking some numbers of partridges, 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 short necks and short slender bills that in some species feature fleshy ceres. They primarily ...
s and crow
A crow is a bird of the genus '' Corvus'', or more broadly a synonym for all of ''Corvus''. Crows are generally black in colour. The word "crow" is used as part of the common name of many species. The related term "raven" is not pinned scientific ...
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 too be taken occasionally including various rodents, hare
Hares and jackrabbits are mammals belonging to the genus ''Lepus''. They are herbivores, and live solitarily or in pairs. They nest in slight depressions called forms, and their young are able to fend for themselves shortly after birth. The gen ...
s, mustelid
The Mustelidae (; from Latin ''mustela'', weasel) are a family of carnivorous mammals, including weasels, badgers, otters, ferrets, martens, minks and wolverines, among others. Mustelids () are a diverse group and form the largest family in t ...
s, hedgehog
A hedgehog is a spiny mammal of the subfamily Erinaceinae, in the eulipotyphlan family Erinaceidae. There are seventeen species of hedgehog in five genera found throughout parts of Europe, Asia, and Africa, and in New Zealand by introduction ...
s and even other large predators such as red foxes 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
The greylag goose or graylag goose (''Anser anser'') is a species of large goose in the waterfowl family Anatidae and the type species of the genus ''Anser (bird), Anser''. It has mottled and barred grey and white plumage and an orange beak and ...
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 average prey size has also been reported more highly.[
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 a wild cat species endemic to the Iberian Peninsula in southwestern Europe. It is listed as Endangered on the IUCN Red List. In the 20th century, the Iberian lynx population had declined because of overhun ...
. 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'') is a large raptor in the family Accipitridae and distributed through much of temperate Eurasia. It is also known as the black vulture, monk vulture and Eurasian black vulture. With a body length of ...
, the largest accipitrid in the world. Healthy, free-flying Spanish imperial eagles are apex predator
An apex predator, also known as a top predator, 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 highest trophic lev ...
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 IUCN. Threats include loss of habitat
Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...
, human encroachment, collisions with pylons
Pylon may refer to:
Structures and boundaries
* Pylon (architecture), the gateway to the inner part of an Ancient Egyptian temple or Christian cathedral
* Pylon, a support tower structure for suspension bridges or highways
* Pylon, an orange mar ...
(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.
By the 1960s it had become a critically endangered 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 c. 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.[Tintó, A., Real, J., & Mañosa, S. (2010). ''Predicting and correcting electrocution of birds in Mediterranean areas''. Journal of Wildlife Management, 74(8), 1852-1862.]
Notes
References
*
*
* Ferguson-Lees, James & Christie, David A. (2001): ''Raptors of the World''. Houghton Mifflin, Boston. .
* Ferrer, Miguel (2001): ''The Spanish Imperial Eagle''. Lynx Edicions, Barcelona. .
*
*
*
* Schuhmacher, Eugen (1973): ''Europe's Paradises''
*
External links
BirdLife Species Factsheet
{{Authority control
Spanish imperial eagle
The Spanish imperial eagle (''Aquila adalberti''), also known as 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 “epaulet ...
Birds of Southern Europe
Fauna of the Iberian Peninsula
Birds of North Africa
Spanish imperial eagle
The Spanish imperial eagle (''Aquila adalberti''), also known as 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 “epaulet ...
Spanish imperial eagle
The Spanish imperial eagle (''Aquila adalberti''), also known as 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 “epaulet ...