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Spanish Imperial Eagle
Aquila adalberti

Status: Vulnerable

Population Trend: Increasing.

Other Names: Adalbert's Eagle, Iberian Imperial Eagle, Imperial Eagle.

Aquila adalberti
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Distribution: Palearctic. Central and southwestern SPAIN, PORTUGAL, and northwestern ALGERIA (formerly); vagrants have recently occurred in NETHERLANDS, FRANCE, MOROCCO, and SENEGAL. more....

Subspecies: Monotypic.

Taxonomy: The molecular phylogenetic analyses of Helbig et al. (op cit.) and Lerner and Mindell (2005), based on DNA sequences from both mitochondrial and nuclear genes, indicated that A. heliaca (and presumably this species) forms a monophyletic group with A. nipalensis and A. rapax. The latter authors recommended that a taxonomic revision be undertaken to show the distinctiveness of this group from other Aquila eagles. This species was formerly considered to be a race of Aquila heliaca (e.g., Brown and Amadon 1968, Stresemann and Amadon 1979), but recent authors have treated the two as separate species based on morphological, ecological, and molecular differences (Hiraldo et al. 1976, Gonzalez et al. 1989, Seibold et al. 1996, Helbig et al. 2005). Gonzales et al. 1989 and Gonzalez 1991 suggested that the two forms may have been parapatric as recently as the middle of the 19th century, but the cytochrome b gene study of Seibold et al. (1996) indicated that there was no evidence of gene flow between these populations since they became separated during the Pleistocene. Martínez-Cruz and Godoy (2007) found that the split occurred much more recently (Holocene or very late Pleistocene) than thought, based on evidence from the nuclear genome, which showed male-mediated gene flow from the Eastern Imperial EAgle to the Spanish Imperial Eagle. more....

Movements: Non-migratory, but juveniles may disperse widely from breeding areas (Ferrer 2001, Bildstein 2006). Spanish birds occasionally cross the Straits and winter in northern Morocco, and the frequency of such migrants has increased in recent years (Thévenot et al. 2003). Recent satellite tracking has indicated that birds may disperse as far south as Senegal, and a second-year bird was recorded in The Netherlands in May 2007 (Weenink et al. 2011).

Habitat and Habits: Historically, this species inhabited woodlands, plains, and marshes in Spain (Valverde 1960, González et al. 1990, Bisson et al. 2002). During the periods of its lowest numbers, it was confined mainly to mountainous areas, but more recently the population has expanded mostly in alluvial plains areas (González et al. 2008). In Morocco, it occurs in forested areas on plains and hills, especially open Cork Oak woodlands surrounding lowland marshes (Thévenot et al. 2003).

Food and Feeding Behavior: In much of Spain, rabbits are the most important prey item, but in wetter areas, birds up to the size of flamingos are mainly taken.

Breeding: Breeding begins in mid-February.The nest is a large structure of sticks, which is placed in a tree, rarely on an electricity pylon (González 1991), but never on a cliff. Clutch size is 1-4 eggs, usually 2 or 3. Almost all incubation is done by the female, with the male incubating only during changeovers involving food provision (Margalida et al. 2007). Incubation begins with the laying of the first age, and the incubation period is 39-42 days (Margalida et al. 2007). Most (65%) of the food is brought to the nest by the male, both during incubation and chick-rearing, but female nest attendance decreases over time (Margalida et al. op cit.). This species exhibits facultative siblicide, and sibling competition and aggression are the main causes of nestling mortality, accounting for 54.8% of nestling deaths in the comprehensive study by Margalida et al. (op cit.). Replacement clutches may be laid when a nest is lost during the early part of the incbuation period. more....

Conservation: Populations are very small within its limited range, but they were stable from 1970-1990 and expanded increased considerably in numbers and extent of range in Spain by 2004 (González et al. 2008). Interestingly, the Spanish population has increased more outside protected areas than within, probably a reflection of changing attitudes, which have led to decreased direct persecution (González et al. op cit.). Historically, the species was shot relentlessly, almost to the point of extinction, poisoned intentionally, and some were caught in traps. It also decreased after 1989, when the population of wild rabbits, a principal prey item, was affected by viral haemorrhagic disease (RHD). It declined radically in a few years, causing great concern for the prospects of the eagle (González 1996). Habitat fragmentation as a result of deforestation for agriculture and timber has had negative impacts on nesting pairs, and the ingestion of lead ammunition fragements from prey has also been a problem. More recently, the main non-natural causes of mortality have been electrocution and poisoning, both anthropogenic in origin, but of an accidental nature (González et al. 2007). This species is now categorized as Vulnerable by BirdLife International and as Endangered in Spain (González and Oria 2004). more....

Population Estimates: González et al. (2008) provided a detailed history of population trends in this species in Spain. The population was estimated at 50 breeding pairs in the early 1960s (Bijleveld 1974), 30 pairs in 1970 (Simon and Geroudet 1970), and a more thorough census conducted from 1971 and 1974 located 38 occupied territories. Later estimates included 60 breeding pairs in 1975 (Garzón 1977), 125 in 1988 (Collar and Andrew 1988), 104 in De Juana (1989), 146 in 1997 (Purroy 1997), 131 in 2000 (SEO BirdLife), and 175 to 200 in 2003 (González and Oria 2003, Martí and Del Moral 2003). BirdLife International/European Bird Census Council (2000) reported an estimate of 131 breeding pairs in 2000, and a nationwide survey in Spain in 2004 located 198 pairs (González et al. op cit.). BirdLife International (2009) estimates the total population of mature individuals at 300 to 400 individuals.

Important References: 
Comisión Nacional de Protección de la Naturaleza. 2001. [Strategy for the
  conservation of the Spanish Imperial Eagle (Aquila adalberti) in Spain].
  Ministerio de Medio Ambiente, Madrid, Spain. (In Spanish)
Ferguson-Lees, J., and D.A. Christie. 2001. Raptors of the world. Houghton
  Mifflin, Boston, MA.
Ferrer, M. 2001. The Spanish Imperial Eagle. Lynx Edicions, Barcelona,
González, L.M. 1991. [Natural history of the Spanish Imperial Eagle
  (Aquila adalberti Brehm 1861)]. Colección Téchnica, ICONA, Madrid, Spain.
  (In Spanish)
González, L.M. 1996. Action plan for the Spanish Imperial Eagle (Aquila
) in Europe. Pp. 175-189 in B. Heredia, L. Rose, and M. Painter
  (eds.), Globally threatened birds in Europe action plans. Council of Europe
  and BirdLife International, Strasbourg, France.
González, L.M., and A. Margalida (eds.). 2008. Conservation biology of the
  Spanish Imperial Eagle (Aquila adalberti). Organismo Autonomo Parques
  Nacionales, Ministerio de Medio Ambiente y Medio Marino y Rural, Madrid,
González, L.M., J. Oria, R. Sánchez, A. Margalida, A. Aranda, L. Prada,
  J. Caldera, and J.I. Molina.
2008. Status and habitat changes in the
  endangered Spanish Imperial Eagle Aquila adalberti population during
  1974-2004: implications for its recovery. BirdLife Conservation
  International 18:242-259.
Hiraldo, F., M. Delibes, and J. Calderon. 1976. [On the taxonomic status
  of the Spanish Imperial Eagle]. Doñana, Acta Vertebrata 3:171-180. (In
Meyburg, B.-U. 1989. The Spanish Imperial Eagle Aquila (heliaca)
: its biology, status and conservation. Pp. 225-268 in B.-U.
  Meyburg and R.D. Chancellor (eds.), Raptors in the modern world. World
  Working Group for Birds of Prey and Owls, Berlin.
Meyburg, B.U. 1994. Spanish Imperial Eagle. P. 194 in del Hoyo, J., A.
  Elliott, and J. Sargatal (eds). Handbook of birds of the world. Vol. 2. New
  World vultures to guineafowl. Lynx Edicions, Barcelona, Spain. more....

Sites of Interest:
Programa de Conservación del Águila Imperial Ibéri
Details of the SEO/BirdLife conservation program for the Spanish Imperial Eagle.
BirdLife International
Information on current status and recommended conservation actions.
Spanish Imperial Eagle photos.
Spanish Imperial Eagle
Species account.

Ferrer, Miguel
Jais, Markus
Margalida, Antoni

Last modified: 4/27/2011

Recommended Citation: Global Raptor Information Network. 2014. Species account: Spanish Imperial Eagle Aquila adalberti. Downloaded from http://www.globalraptors.org on 18 Apr. 2014

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