Spanish Imperial Eagle, Aquila adalberti
Spanish Imperial Eagle, Spain, May 2009, © Markus Jais
English: Spanish Imperial Eagle
Scientific: Aquila adalberti
German: Spanischer Kaiseradler
Spanish: Águila imperial ibérica
French: Aigle ibérique
Taxonomy and Subspecies
Formerly considered a subspecies of the Eastern Imperial Eagle. Today treated as a seperate species. Forms a superspecies with the Eastern Imperial Eagle. The closest relatives of the Spanish and Eastern Imperial Eagle are probably the Steppe Eagle Aquila nipalensis and the Tawny Eagle Aquila rapax . [GRIN 2009]
Length: 78-82 cm
Wingspan: 180-210 cm
Weight: 2,500-3,500 g
More than 40 years in captivity. [Mebs & Schmidt 2014]
Mostly found in Mediterranean forests but also in marshes like in the Doñana national park. The Spanish Imperial Eagle can also be found in “Dehesas”, a typical wooded pastureland found in Spain. Enough prey, especially rabbits are important.
Sometimes, the Spanish Imperial Eagle can also be found in agricultureal areas, similar to the Eastern Imperial Eagle. In Castilla La Mancha, there is a nest in a small group of poplar trees surrounded by agricultural fields and olive plantations and only a few hundred meters away from a farm (pers. observation). There are many rabbits in that territory. If left alone, the eagles can live in places like that and successfully raise young.
Restricted to the Iberian Peninsula. Almost the whole world population breeds in Spain. Recently, a few pairs recolonised Portugal. Was considered extinct in Morocco, but there was a breeding in 1995. Maybe there are still a few pairs left. Also bred in Algeria in the 19th century, but now extinct. [GRIN 2009]
Adult Spanish Imperial Eagles are sedentary birds and stay in their territory all year. Juvenile birds disperse after becoming independent. Some birds breed close to their birth site when they are old enough, others settle farther away from their birth site. This latter is called natal dispersal. In a study in Spain that involved tracking 84 nestlings between 1990 and 2002, the mean natal dispersal distance was 101.2 km with a maximum of 310 km (255 km for females) [Gonzáles & Margalida 2008].
[Gonzáles et al. 1989] describe 3 phases of dispersal for the Spanish Imperial Eagle:
- 1) Exploratory flights with return to the natal area (within 3 months of fledging, that is 4-6 months of age).
- 2) Longer distance flights where some birds can establish temporary territories (between 7 and 15 months of age).
- 3) Return to the vicinity of the natal area (after being 16 month or older).
During the dispersal phase the eagles often leave protected areas and therefore are often exposed to many human related threats (see below).
Breeding and Reproduction
Normally starts breeding with 4-5 years. Nests are normally built on trees, recently some pairs started using electricity pylons. Normally 1-4 eggs are laid. The incubation period is about 44 days and the young stay in the nest for about 75 days.
After fledging the young stay within their natal area for another 116-162 days before dispersing. [HBW Alive 2014], [Mebs & Schmidt 2014].
Food and hunting
The most important prey is the rabbit. In a study in the Montes de Toledo (Castilla-La Manche, Spain) the pellets of Spanish Imperial Eagles were studied. In 93%, remains of rabbits were found. Other important prey was carrion (found in 20% of the pellets), pigeons (8.4%), other birds (10%), hare (2%), reptiles (1.8) and partridge (0.6%) [Castaño López 2005]. That clearly shows how important the rabbit is for the species.
In the Doñana National Park more waterfowl like Greylag Geese, Coots and Mallards are hunted, as well as Magpies and Wood Pigeons [Mebs & Schmidt 2014].
One of the rarest raptors in the world. In 1974 only about 50 pairs were counted [Castaño López 2005]. But since then the population has increased and in 2008 253 territories were occupied, 4 in Portugal, the rest in Spain. 310 young eagles fledged in 2008. [Gonzáles 2009].
In 2010, 282 pairs were observed, 279 in Spain and 3 in Portugal. This is 16 pairs more than in 2009. 341 young fledged, the highest number ever recorded [SEO 2011].
On of the most serious threats is electrocution. In 2008, 33 electrocuted Spanish Imperial Eagles were found [Gonzáles 2009]. Despite work to make powerlines safe in many areas, there are still many eagles dying because of electrocution. The expanding population and dispersing juveniles visit new areas where powerlines have not yet been made safe.
Poisoning is another serious problem. Many eagles and vultures are poisoned in Spain every year. Often the poisoning is targeted at the raptors themselves. In other cases the target species are mammals like foxes but eagles also eat carrion and so die, too.
In a study that examined the death of 267 Spanish Imperial Eagles between 1989 and 2004, 91.7% of the causes of mortality (where the cause of death could be determined) were of human origin. Electrocution and poisoning were by far the most common causes of death. 115 Spanish Imperial Eagles were electrocuted and 74 were poisoned. Other causes of death were shooting (16 cases) and disease (13 cases) [Gonzáles & Margalida 2008].
Illegal poisoning must be stopped. Public education and better law enforcement are necessary. Powerlines should all be made safe for birds. Not only in the breeding areas, but also in the dispersal areas where many juvenile and immature birds can be found after they leave their natal area. In Spain, several organisations like WWF or SEO/BirdLife Spain are working on conservation programs for the Spanish Imperial Eagle. The national and some regional governments are also working to protect the species.
Valuable habitat must be protected. Roads or windfarms should not be build in valuable habitat, close to nests or in dispersal areas.
The recent population increase is encouraging. If poisoning and electrocution can be reduced significantly, the population should be able to increase a lot more.
Status Global Raptor Information Network
Interviews about the Spanish Imperial Eagle
[Forsman 1999] Forsman, Dick (1999). The Raptors of Europe and the Middle East. A Handbook of Field Identification. Poyser
[Gonzáles et al. 1989] Gonzáles, L.M. & Heredia, Borja & Gonzáles Jose L. & Alonso, Juan C. (1989). Juvenile dispersal of Spanish Imperial Eagles. Journal of Field Ornithology 60 (3) 369 – 379.
[Gonzáles & Margalida 2008] Gonzáles, L.M. & Margalida, A. (2008). Biología de la conservación del águila imperial ibérica (Aguila adalberti). Conservation biology of the Spanish imperial eagle (Aquila adalberti). Organismo Autónomo Parques Nacionales. Ministerio de Medio Ambiente y Medio Marion y Rural. Madrid.
[Gonzáles 2009]. Gonzáales, Luis Mariano (2009). Más de 250 parejas: continúa la recuperación del águila imperial. Quercus. Cuaderno (issue) 279.
[GRIN 2009] Global Raptor Information Network. 2009. Species account: Spanish Imperial Eagle Aquila adalberti. Downloaded from http://www.globalraptors.org on 27 Feb. 2009
[HBW Alive 2014] del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.) (2014). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/ on 9 November 2014).
[Mebs & Schmidt 2014] Mebs, Theodor & Schmidt, Daniel (2014). Die Greifvögel Europas, Nordafrikas und Vorderasiens (2. Auflage). Kosmos Verlag.
[SEO 2011] El MARM, las CCAA y Portugal analizan los avances conseguidos en la conservación del águila imperial ibérica. Downloaded from http://126.96.36.199/aguilaimperial/noticia.php?id=51&fi=1 on 09 April 2011.
Castaño López, Juan Pablo (2005). El Águila Imperial Ibérica en Castilla La Mancha – estatus, ecología y conservación. Graphitis Impresores. Madrid.Forsman, Dick (1999). The Raptors of Europe and the Middle East. A Handbook of Field Identification. Poyser. London.
Gonzáles, L.M. y Margalida, A. (2008). Biología de la conservación del águila imperial ibérica (Aguila adalberti). Conservation biology of the Spanish imperial eagle (Aquila adalberti). Organismo Autónomo Parques Nacionales. Ministerio de Medio Ambiente y Medio Marion y Rural. Madrid.
Mebs, Theodor & Schmidt, Daniel (2014). Die Greifvögel Europas, Nordafrikas und Vorderasiens, 2. Auflage. Kosmos Verlag, Stuttgart.
Programa de Conservación del Águila Imperial Ibérica
Conservation program for the Spanish Imperial Eagle of SEO/BirdLife Spain