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Aquila adalberti

Aquila adalberti (*)

Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Megaclassis: Osteichthyes
Cladus: Sarcopterygii
Cladus: Rhipidistia
Cladus: Tetrapodomorpha
Cladus: Eotetrapodiformes
Cladus: Elpistostegalia
Superclassis: Tetrapoda
Cladus: Reptiliomorpha
Cladus: Amniota
Classis: Reptilia
Cladus: Eureptilia
Cladus: Romeriida
Subclassis: Diapsida
Cladus: Sauria
Infraclassis: Archosauromorpha
Cladus: Crurotarsi
Divisio: Archosauria
Cladus: Avemetatarsalia
Cladus: Ornithodira
Subtaxon: Dinosauromorpha
Cladus: Dinosauriformes
Cladus: Dracohors
Cladus: Dinosauria
Ordo: Saurischia
Cladus: Eusaurischia
Subordo: Theropoda
Cladus: Neotheropoda
Cladus: Averostra
Cladus: Tetanurae
Cladus: Avetheropoda
Cladus: Coelurosauria
Cladus: Tyrannoraptora
Cladus: Maniraptoromorpha
Cladus: Maniraptoriformes
Cladus: Maniraptora
Cladus: Pennaraptora
Cladus: Paraves
Cladus: Eumaniraptora
Cladus: Avialae
Infraclassis: Aves
Cladus: Euavialae
Cladus: Avebrevicauda
Cladus: Pygostylia
Cladus: Ornithothoraces
Cladus: Ornithuromorpha
Cladus: Carinatae
Parvclassis: Neornithes
Cohors: Neognathae
Cladus: Neoaves
Ordo: Accipitriformes

Familia: Accipitridae
Subfamilia: Aquilinae
Genus: Aquila
Species: Aquila adalberti

Aquila adalberti C. L. Brehm, 1861

Brehm, C.L. Etwas über die Adler. In: Bericht über die XIII. Versammlung der Deutschen Ornithologischen-Gesellschaft zu Stuttgart vom 17.–20. September 1860. C. Hoffmann, Stuttgart 1861, S. 55–62.
IUCN: Aquila adalberti (Vulnerable)

Vernacular names
català: Àguila imperial
čeština: Orel iberský
Deutsch: Spanischer Kaiseradler
Ελληνικά: Ισπανικός βασιλαετός
English: Spanish Imperial Eagle
Esperanto: Ibera aglo
español: Águila Imperial Ibérica
suomi: Iberiankeisarikotka
français: Aigle ibérique
italiano: Aquila imperiale spagnola
日本語: イベリアカタシロワシ
Nederlands: Spaanse keizerarend
polski: Orzeł iberyjski
português: Águia-imperial-ibérica
русский: Испанский орёл-могильник
svenska: Spansk kejsarörn
中文: 西班牙帝鵰

The Spanish imperial eagle (Aquila adalberti), also known as the Iberian imperial eagle, Spanish eagle, or Adalbert's eagle, is a species of eagle native to the Iberian Peninsula. The binomial commemorates Prince Adalbert of Bavaria.

Formerly,[3] 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,[4] ecology,[5] and molecular characteristics.[6][7]

A captive subadult Spanish imperial eagle

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 2.5 to 4.8 kg (5.5 to 10.6 lb). The average weight of males in a sample of 10 was 3.19 kg (7.0 lb) while that of 17 females was found to be 3.43 kg (7.6 lb). Meanwhile, another sample of 10 unsexed adults weighed an average of 3.93 kg (8.7 lb). 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 72 to 85 cm (28 to 33 in) and a wingspan of 177 to 220 cm (5 ft 10 in to 7 ft 3 in).[8][9][10][11][12] A typical wingspan for a male is reportedly about 190 cm (6 ft 3 in) while for a female may be about 210 cm (6 ft 11 in).[13]

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.[14]

Adult Spanish imperial eagle

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.[14] Stable occurrence in Morocco is disputed[15] but immature birds during the dispersion period regularly visit Morocco.[16]

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.[17] Vagrant birds have even reached Mauritania and Senegal.[18] North of its natural range, vagrants have reached as far as the Netherlands in one rare occasion.[19]
A Spanish imperial eagle on its nest tending to its eaglet.

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.[20] 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 1.5 m (4.9 ft) across at first build, which will increase in time, especially in mature 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.[14][21][22]
Aquila adalberti - MHNT

It feeds mainly on European rabbits, which comprised about 58% of this species' diet before myxomatosis 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, pigeons and crows 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, hares, mustelids, hedgehogs 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 3.3 kg (7.3 lb), such as foxes, greylag geese or white storks, but mean prey mass is relatively low, especially in areas with fewer rabbits. One study reported mean prey mass as 450 g (0.99 lb) locally, though average prey size has also been reported more highly.[10][23]

The Spanish imperial eagle is one of several rabbit-favoring birds of prey in Spain along with the similarly specialized Iberian lynx. 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, 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 largest accipitrid in the world. Healthy, free-flying Spanish imperial eagles are apex predators, 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.[10][24][25][26]
Juvenile Spanish imperial eagle in flight

The species is classified as Vulnerable by IUCN.[1] Threats include loss of habitat, 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)[27] 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 and, most recently, rabbit haemorrhagic disease.[17]

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.[1][28] 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.[1][29]

BirdLife International (2019). "Aquila adalberti". IUCN Red List of Threatened Species. 2019: e.T22696042A152593918. doi:10.2305/IUCN.UK.2019-3.RLTS.T22696042A152593918.en. Retrieved 19 November 2021.
"Appendices | CITES". Retrieved 14 January 2022.
Sangster et al. 2002
Cramp & Simmons 1980
Meyburg 1994
Seibold et al. 1996
Padilla et al. 1999
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.
García-Montijano, M., García, A., Lemus, J. A., Montesinos, A., Canales, R., Luaces, I., & Pereira, P. (2002). Blood chemistry, protein electrophoresis, and hematologic values of captive Spanish imperial eagles (Aquila adalberti). Journal of Zoo and Wildlife Medicine, 33(2), 112-117.
Borrow, N. (2020). Field Guide to Birds of Western Africa. Bloomsbury Publishing.
Mendi, M. B., Aliende, M. M., & Benito, M. B. (2004). Aves de Fresno de Torote y Serracines. Entrelineas Editores.
Ferguson, L. J., & Christie, D. A. (2001). Raptors of the World. London (UK): Christopher Helm.
Gonzalez et al. 1989, p. 89
Amezian, M., Irizi, A., Errati, A., Loran, H., El Khamlichi, R., Morandini, V., González, D. G., Garrido, J. R. (2015). Spanish Imperial Eagles and other eagles found electrocuted in Morocco and proposition of correction measures. figshare. doi:10.6084/m9.figshare.1613292 Retrieved 28 November 2015.
Las águilas imperiales vuelven a Marruecos y mueren electrocutadas|Ciencia|EL PAÍS
González, L. M. & Oria, J. (2004). Águila Imperial Ibérica Aquila adalberti. In: Madroño, A., González C. & Atienza, J. C. (editors): Libro rojo de las aves de España: 145–152. Dirección General para la Biodiversidad & SEO/BirdLife, Madrid.
Weenink, R.; van Duivendijk, N.; Ebels, E. B. (2011). "[Spanish Imperial Eagle at Loozerheide in May 2007]". Dutch Birding. 33: 94–102.
González, L. M., Bustamante, J., & Hiraldo, F. (1992). Nesting habitat selection by the Spanish imperial eagle Aquila adalberti. Biological Conservation, 59(1), 45-50.
Margalida, A., González, L. M., Sanchez, R., Oria, J., Prada, L., Caldera, J., & Molina, J. I. (2007). A long-term large-scale study of the breeding biology of the Spanish imperial eagle (Aquila adalberti). Journal of ornithology, 148(3), 309-322.
Gonzalez, L. M., Heredia, B., Gonzalez, J. L., & Alonso, J. C. (1989). Juvenile Dispersal of Spanish Imperial Eagles (Dispersión de los Jóvenes de Aquila adalberti). Journal of Field Ornithology, 369-379.
Sánchez, R., Margalida, A., González, L. M., & Oria, J. (2008). Biases in diet sampling methods in the Spanish Imperial Eagle Aquila adalberti. Ornis Fennica, 85(3), 82-89.
González, L. M. (1996). Action plan for the Spanish imperial eagle (Aquila adalberti). Globally Threatened Birds in Europe: Action Plans (Council of Europe and BirdLife International Strasbourg 1996), 175-189.
Oria, J (1999). "Spanish Imperial Eagle Aquila adalberti attacks and kills a Cinereous Vulture Aegypius monachus". Vulture News. 40: 37.
Ferrer, M., & Calderón, J. (1990). The Spanish imperial eagle Aquila adalberti CL Brehm 1861 in Doñana National Park (south west Spain): a study of population dynamics. Biological conservation, 51(2), 151-161.
Salvando al águila imperial ibérica|Ciencia|EL PAÍS
Ferrer, M., & Negro, J. J. (2004). The near extinction of two large European predators: super specialists pay a price. Conservation Biology, 18(2), 344-349.

Tintó, A., Real, J., & Mañosa, S. (2010). Predicting and correcting electrocution of birds in Mediterranean areas. Journal of Wildlife Management, 74(8), 1852-1862.


Gonzalez, L. M.; Hiraldo, F.; Delibes, M. & Calderon, J. (June 1989). "Zoographic support for the Spanish Imperial Eagle as a distinct species". Bulletin of the British Ornithologists' Club. 109 (2): 86–93. ISSN 0007-1595.

Cramp, S. & Simmons, K. E. L. (1980). Birds of the Western Palearctic, Vol. 2. Oxford, UK: Oxford University Press.
Ferguson-Lees, James & Christie, David A. (2001): Raptors of the World. Houghton Mifflin, Boston. ISBN 0-618-12762-3.
Ferrer, Miguel (2001): The Spanish Imperial Eagle. Lynx Edicions, Barcelona. ISBN 84-87334-34-2.
Meyburg, B. U. (1994). "210 & 211: Imperial Eagles". In del Hoyo, Josep; Elliott, Andrew & Sargatal, Jordi (eds.). Handbook of Birds of the World, Volume 2: New World Vultures to Guineafowl. Barcelona, Spain: Lynx Edicions. pp. 194–195, plate 20. ISBN 84-87334-15-6.
Padilla, J. A.; Martinez-Trancón, M.; Rabasco, A. & Fernández-García, J. L. (1999). "The karyotype of the Iberian imperial eagle (Aquila adalberti) analyzed by classical and DNA replication banding". Cytogenetics and Cell Genetics. 84 (1–2): 61–66. doi:10.1159/000015216. PMID 10343105. S2CID 41181626.
Sangster, George; Knox, Alan G.; Helbig, Andreas J. & Parkin, David T. (2002). "Taxonomic recommendations for European birds". Ibis. 144 (1): 153–159. doi:10.1046/j.0019-1019.2001.00026.x.
Schuhmacher, Eugen (1973): Europe's Paradises
Seibold, I.; Helbig, A. J.; Meyburg, B. U.; Negro, J. J. & Wink, M. (1996). "Genetic Differentiation and Molecular Phylogeny of European Aquila Eagles (Aves: Falconiformes) According to Cytochrome-b Nucleotide Sequences" (PDF). In Meyburg, B. U. & Chancellor, R. D. (eds.). Eagle Studies. Berlin: World Working Group on Birds of Prey. pp. 1–15.

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