Spanish imperial eagle

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Spanish imperial eagle
Aguila Imperial Entrando Al Posadero (125891767).jpeg
A Spanish imperial eagle flying down to its perch
CITES Appendix I (CITES) [2]
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Accipitriformes
Family: Accipitridae
Genus: Aquila
Species:
A. adalberti
Binomial name
Aquila adalberti
Aquila adalberti distr.PNG
Synonyms

Aquila heliaca adalberti

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. [3]

Contents

Formerly, [4] 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, [5] ecology, [6] and molecular characteristics. [7] [8]

Description

A captive subadult Spanish imperial eagle Aquila adalberti.jpg
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). [9] [6] 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). [10]

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. [11]

Distribution and habitat

Adult Spanish imperial eagle Aguila imperial iberica.jpg
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. [11] Stable occurrence in Morocco is disputed [12] but immature birds during the dispersion period regularly visit Morocco. [13]

Rising numbers of vagrant birds born in Spain and then electrocuted in Morocco have been noted; [14] 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. [15] Vagrant birds have even reached Mauritania and Senegal. [16] North of its natural range, vagrants have reached as far as the Netherlands in one rare occasion. [17]

Behaviour and ecology

A Spanish imperial eagle on its nest tending to its eaglet. 5159 Aguila imperial y pollo.jpg
A Spanish imperial eagle on its nest tending to its eaglet.

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. [18] 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 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. [11] [19] [20]

Egg, Museum de Toulouse Aquila adalberti MHNT.ZOO.2010.11.93.5.jpg
Egg, Muséum de Toulouse

Food and feeding

The Spanish imperial eagle 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 have 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 also be taken 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 a larger average prey size has also been reported. [21] [22]

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. [21] [23] [24] [25]

Conservation

Juvenile Spanish imperial eagle in flight Aquila adalberti 2014-02-08 1.jpg
Juvenile Spanish imperial eagle in flight

The species is classified as Vulnerable by the International Union for Conservation of Nature. [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) [26] 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. [15]

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] [27] 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. [1] [28]

Related Research Articles

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Eagle is the common name for the golden eagle, bald eagle, and other birds of prey in the family Accipitridae. Eagles belong to several groups of genera, some of which are closely related. True eagles comprise the genus Aquila. Most of the 68 species of eagles are from Eurasia and Africa. Outside this area, just 14 species can be found—two in North America, nine in Central and South America, and three in Australia.

<span class="mw-page-title-main">Accipitridae</span> Family of birds of prey

The Accipitridae is one of the three families within the order Accipitriformes, and is a family of small to large birds of prey with strongly hooked bills and variable morphology based on diet. They feed on a range of prey items from insects to medium-sized mammals, with a number feeding on carrion and a few feeding on fruit. The Accipitridae have a cosmopolitan distribution, being found on all the world's continents and a number of oceanic island groups. Some species are migratory. The family contains 255 species which are divided into 70 genera.

<span class="mw-page-title-main">Golden eagle</span> Species of eagle

The golden eagle 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 of prey in the Northern Hemisphere. These birds are dark brown, with lighter golden-brown plumage on their napes. Immature eagles of this species typically have white on the tail and often have white markings on the wings. Golden eagles use their agility and speed combined with powerful feet and large, sharp talons to hunt a variety of prey, mainly hares, rabbits, and marmots and other ground squirrels. Golden eagles maintain home ranges or territories that may be as large as 200 km2 (77 sq mi). They build large nests in cliffs and other high places to which they may return for several breeding years. Most breeding activities take place in the spring; they are monogamous and may remain together for several years or possibly for life. Females lay up to four eggs, and then incubate them for six weeks. Typically, one or two young survive to fledge in about three months. These juvenile golden eagles usually attain full independence in the fall, after which they wander widely until establishing a territory for themselves in four to five years.

<span class="mw-page-title-main">Eastern imperial eagle</span> Species of bird

The eastern imperial eagle 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 and East Asia. Like all eagles, the eastern imperial eagle is a member of the family Accipitridae. Furthermore, its feathered legs mark it as a member of the subfamily Aquilinae. It is a large, dark-colored eagle, with a resemblance to other members of the genus Aquila but it is usually the darkest species in its range. This is an opportunistic predator that mostly selects smallish mammals as prey but also a fairly large proportion of birds, reptile and other prey types, including carrion. Compared to other Aquila eagles, it has a strong preference for the interface of tall woods with plains and other open, relatively flat habitats, including the wooded mosaics of the steppe. Normally, nests are located in large, mature trees and the parents raise around one or two fledglings. The global population is small and declining due to persecution, loss of habitat and prey. It has therefore been IUCN Red Listed as Vulnerable since 1994.

<span class="mw-page-title-main">Egyptian vulture</span> Species of Old World vultures of the genus Neophron

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<span class="mw-page-title-main">Wedge-tailed eagle</span> Bird of prey within the genus Aquila

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<span class="mw-page-title-main">Cinereous vulture</span> Species of bird

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<span class="mw-page-title-main">Tawny eagle</span> Species of bird

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<span class="mw-page-title-main">Steppe eagle</span> Species of bird

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<span class="mw-page-title-main">Martial eagle</span> Species of bird

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<span class="mw-page-title-main">Aquilinae</span> Subfamily of birds

The Aquilinae are a subfamily of eagles of the family Accipitridae. The general common name used for members of this subfamily is "booted eagle", although this is also the common name of a member of the subfamily. At one point, this subfamily was considered inclusive with the Buteoninae based probably on some shared morphological characteristics. However, research on the DNA of the booted eagles has shown that they are a monophyletic group that probably have had millions of years of separation from other extant forms of accipitrid.

<span class="mw-page-title-main">Dietary biology of the golden eagle</span> Hunting and dietary habits of the golden eagle

The golden eagle is one of the most powerful predators in the avian world. One author described it as "the pre-eminent diurnal predator of medium-sized birds and mammals in open country throughout the Northern Hemisphere". Golden eagles usually hunt during daylight hours, but were recorded hunting from one hour before sunrise to one hour after sunset during the breeding season in southwestern Idaho. The hunting success rate of golden eagles was calculated in Idaho, showing that, out of 115 hunting attempts, 20% were successful in procuring prey. A fully-grown golden eagle requires about 230 to 250 g of food per day. In the life of most eagles, there are cycles of feast and famine, and eagles have been known to go without food for up to a week. Following these periods without food, they will then gorge on up to 900 g (2.0 lb) at one sitting. The powerful talons of the golden eagle ensure that few preys can escape them once contact is made. The talons of this species exert approximately 440 pounds per square inch (3 MPa) of pressure, around 15 times more pressure than is exerted by the human hand, although some claim that the largest individual females may reach a pressure of 750 psi (5.2 MPa). It has been claimed that the golden eagle can lift more than its own body weight in flight. However, other sources claim that a hare, marmot or deer calf weighing 4 kg (8.8 lb) is a struggle for even a large female to carry and that prey much over 2 kg (4.4 lb) would require favorably high wind conditions.

<span class="mw-page-title-main">Dietary biology of the Eurasian eagle-owl</span>

The Eurasian eagle-owl may well be the most powerful extant species of owl, able to attack and kill large prey far beyond the capacities of most other living owls. However, the species is even more marked for its ability to live on more diverse prey than possibly any other comparably sized raptorial bird, which, given its considerable size, is almost fully restricted to eagles. This species can adapt to surprisingly small prey where it is the only kind available and to large prey where it is abundant. Eurasian eagle-owls feed most commonly on small mammals weighing 100 g (0.22 lb) or more, although nearly 45% of the prey species recorded have an average adult body mass of less than 100 g (3.5 oz). Usually 55-80% of the food of eagle-owls is mammalian.

<span class="mw-page-title-main">Reproduction and life cycle of the golden eagle</span>

Golden eagles usually mate for life. A breeding pair is formed in a courtship display. This courtship includes undulating displays by both in the pair, with the male bird picking up a piece of rock and dropping it only to enter into a steep dive and catch it in mid-air, repeating the maneuver 3 or more times. The female takes a clump of earth and drops and catches it in the same fashion. Small sticks may also be used in this display. Compared to the bald eagle, golden eagles do not repeat courtship displays annually and rarely engage in talon-locking downward spirals.

<span class="mw-page-title-main">Status and conservation of the golden eagle</span>

At one time, the golden eagle lived in a great majority of temperate Europe, North Asia, North America, North Africa, and Japan. Although widespread and quite secure in some areas, in many parts of the range golden eagles have experienced sharp population declines and have even been extirpated from some areas. The total number of individual golden eagles from around the range is estimated to range somewhere between 170,000 and 250,000 while the estimated total number of breeding pairs ranges from 60,000 to 100,000. Few other eagle species are as numerous, though some species like tawny eagle, wedge-tailed eagle and bald eagle have total estimated populations of a similar size to the golden eagle's despite having distributions which are more restricted. The world's most populous eagle may be the African fish eagle, which has a stable total population estimated at 300,000 individuals and is found solely in Africa. On a global scale, the golden eagle is not considered threatened by the IUCN.

References

  1. 1 2 3 4 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.
  2. ↑ "Appendices | CITES". cites.org. Retrieved 14 January 2022.
  3. ↑ "Ornithology of Gibraltar, page 171=10 November 2022". openlibrary.
  4. ↑ Sangster et al. 2002
  5. ↑ Cramp & Simmons 1980
  6. 1 2 Meyburg, B.U. (1994). "210 & 211: Imperial Eagles" . In del Hoyo, Josep; Elliott, Andrew; Sargatal, Jordi (eds.). Handbook of Birds of the World. Vol. 2: New World Vultures to Guineafowl. Barcelona, Spain: Lynx Edicions. pp. 194–195, plate 20. ISBN   84-87334-15-6.
  7. ↑ Seibold et al. 1996
  8. ↑ Padilla et al. 1999
  9. ↑ European Raptor Conservation European This is a national bird of Spain Spanish Imperial Eagle, Aquila adalberti. Accessed 17 May 2011
  10. ↑ Mendi, M. B., Aliende, M. M., & Benito, M. B. (2004). Aves de Fresno de Torote y Serracines. Entrelineas Editores.
  11. 1 2 3 Ferguson, L. J., & Christie, D. A. (2001). Raptors of the World. London (UK): Christopher Helm.
  12. ↑ Gonzalez et al. 1989 , p. 89
  13. ↑ 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.
  14. ↑ Garrido, Mohamed Amezian Ali Irizi Abdallah Errati Hicham Loran Rachid El Khamlichi Virginia Morandini Diego García González Jose Rafael (2015). Spanish Imperial Eagles and other eagles found electrocuted in Morocco and proposition of correction measures. Figshare. OCLC   947630527.
  15. 1 2 Las águilas imperiales vuelven a Marruecos y mueren electrocutadas|Ciencia|EL PAÍS
  16. ↑ 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.
  17. ↑ Weenink, R.; van Duivendijk, N.; Ebels, E. B. (2011). "[Spanish Imperial Eagle at Loozerheide in May 2007]". Dutch Birding . 33: 94–102.
  18. ↑ González, L.M.; Bustamante, J.; Hiraldo, F. (1992). "Nesting habitat selection by the Spanish imperial eagle Aquila adalberti". Biological Conservation. 59 (1): 45–50. doi:10.1016/0006-3207(92)90712-V. hdl: 10261/47136 .
  19. ↑ Margalida, A.; González, L.M.; Sánchez, R.; Oria, J.; Prada, L.; Caldera, J.; Aranda, A.; 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. doi:10.1007/s10336-007-0133-5.
  20. ↑ 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. 60 (3): 369–379. JSTOR   4513455.
  21. 1 2 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.
  22. ↑ 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.
  23. ↑ 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.
  24. ↑ Oria, J. (1999). "Spanish Imperial Eagle Aquila adalberti attacks and kills a Cinereous Vulture Aegypius monachus". Vulture News. 40: 37.
  25. ↑ Ferrer, Miguel; Calderón, Juan (1990). "The Spanish imperial eagle Aquila adalberti C. L. Brehm 1861 in Doñana National Park (South West Spain): A study of population dynamics". Biological Conservation. 51 (2): 151–161. doi:10.1016/0006-3207(90)90109-3.
  26. ↑ Salvando al águila imperial ibérica|Ciencia|EL PAÍS
  27. ↑ Ferrer, Miguel; Negro, Juan José (2004). "The near extinction of two large European predators: super specialists pay a price". Conservation Biology. 18 (2): 344–349. JSTOR   3589211.
  28. ↑ Tintó, A.; Real, J.; Mañosa, S. (2010). "Predicting and correcting electrocution of birds in Mediterranean areas". Journal of Wildlife Management. 74 (8): 1852–1862. doi:10.2193/2009-521.

Sources

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