Bonelli’s Eagle, Aquila fasciata
Bonelli’s Eagle, Spain, June 2007 (captive bird), © Markus Jais
English: Bonelli’s Eagle
Scientific: Aquila fasciata
Spanish: Águila perdicera
French: Aigle de Bonelli
Taxonomy and Subspecies
Forms a superspecies with the African Hawk Eagle Aquila spilogaster [Bauer et al. 2005]. The African Hawk Eagle was sometimes considered to be just a subspecies of the Bonelli’s Eagle but is now considered a separate species. Both species were formerly placed in the Genus Hieraaetus but recent research shows that they should now be included in the genus Aguila, as both are closely related to the Verreaux’s Eagle Aquila verreauxii [GRIN 2009, Bauer et al. 2005].
Two subspecies: A. f. fasciata occurs over most of the species’ range and A. f. renschi can be found on the Lesser Sunda Islands. The latter may be a separate species [GRIN 2009].
Length: 65-72 cm
Wingspan: Male 150-160 cm, Female 165-180 cm
Weight: 1,600-2,500 g
32 years in the wild. [Larrey, Roger & Morvan 2007]
In Europe, the Bonelli’s Eagle is a bird of the Mediterranean landscape. It prefers dry and open or half open habitat in mountainous areas.Outside the breeding season it can also be found in lowlands and wetlands where it can hunt waterfowl [Mebs & Schmidt 2006].
Occurs around the Mediterranean and eastwards in Asia in Iran, Arabia, Oman, Turkmenistan, India, southern China, Pakistan. A subspecies (or separate species) lives on the Lesser Sunda Islands (see above under Taxonomy) [GRIN 2009, Mebs & Schmidt 2006].
Adults are sedentary but in winter their range can be bigger than during the breeding seasons [Mebs & Schmidt 2006]. Juveniles disperse more widely, probably to avoid competition for food with the territorial adults.
Breeding and Reproduction
Probably can breed with three years. The adults stay together even outside of the breeding season [Mebs & Schmidt 2006]. Mostly breeds on cliffs but there are also some nests on power poles, for example in Castilla La Mancha (Spain). Large trees are also used in some cases. In Portugal, 64% of the total population nest in trees like Cork Oaks, Pines and large Eucalyptus [Palma 2009].
The Bonelli’s Eagle breeds rather early. Egg laying is normally between the beginning of February and the middle of March [Mebs & Schmidt 2006]. Normally 2 eggs are laid, sometimes 1 or 3. The chicks hatch after 37 to 40 days and stay in the nest between 55 and 70 days [GRIN 2009, Mebs & Schmidt 2006].
Cainism does not seem to be common among Bonelli’s Eagles.
Not every pairs breeds every year.
Food and hunting
Rabbits and Red-legged Partridges form an important diet where they occur [GRIN 2009]. Also takes a lot of other birds like pigeons, crows, ducks, gulls and others up to the size of herons. During the summer, lizards are also taken [Mebs & Schmidt 2006].
The Bonelli’s Eagle is a powerful hunter that is capable of killing large birds like herons or storks (although those birds are not the regular prey). In Morocco a Long-legged Buzzard was killed by a Bonelli’s Eagle [Mebs & Schmidt 2006].
White globally currently not considered threatened, it is one of the most endangered raptors in Europe. BirdLife International evaluates it as Endangered in Europe after a decline of over 20% over two generations [BirdLife International 2004].
The European population is estimated between 1.013 and 1,141 pairs with 733-768 pairs in Spain [SEO 2007]. BirdLife International  estimated the population between 920 and 1.100 pairs with 650-713 in Spain.
Very rare in other European countries. The population in Greece is about 85-105 pairs with over 50% in Crete [HOS 2009, GRIN 2009, BirdLife International 2004]. Portugal has 104 known pairs and a few more so far unconfirmed [Palma 2009].
Other countries have only very small populations (below 50 pairs), Bulgaria (1-3), Italy (13-18) or Cyprus (20-40) [BirdLife International 2004].
In France, in 2009, 29 pairs fledged 28 young eagles [Lecacheur 2009].
In Spain the population seems to be stable in Andalucía, Extremadura and Castilla-La Mancha but declining in the north and along the Mediterranean [SEO 2007].
Many Bonelli’s eagle die because of electrocution. About 50% of all reported dead Bonelli’s Eagles in Spain died because of electrocution [SEO 2007]. In France about 47% died because of electrocution [Lecacheur 2009]
Bonelli’s eagles sometimes kill domestic and homing pigeons and that makes them very unpopular among pigeon fanciers (similar to the Peregrine Falcon). Some hunters also don’t like them because they see the Bonelli’s Eagle (and other raptors) as a threat to game animals like rabbits or the Red-legged Partridge. Because of this, the Bonelli’s Eagle (and other raptors) are often illegally shot or poisoned.
Habitat destruction due to development, road building or forest plantations is also a major problem.
Human disturbance (for example due to recreation) can lead to breeding failure or abandonment of territories. Forest active can also lead to disturbance, for example in southern Portugal [Palma 2009]. The logging of large trees suitable for nesting is another threat [Palma 2009].
The decline of the rabbit because of diseases (for example Myxomatosis) has caused an often dramatic decline in rabbit numbers which has reduced the available prey for Bonelli’s Eagle and other species dependent on rabbits like the Spanish Imperial Eagle or the critically endangered Iberian Lynx.
In order to keep current populations stable or even help them recover and increase, the mortality through electrocution must be eliminated. Many birds die every year because of unsafe power poles.
Power poles must be made safe all across it’s breeding range and also across the dipersal areas of the juvenile birds. Juveniles leaving their natal area can appear almost everywhere in the species’ range including outside of suitable habitat (even if only for a shorter time while moving to better habitat). That means that the dispersing birds can be electrocuted almost everywhere where they fly. Making power poles save would also help many other raptor species and other large birds like storks.
Illegal shooting most be stopped through more education, better control and punishment of those who shot an eagle.
The remaining habitat must be protected incl. those places which are not occupied by the species at the moment but can be in the future if the population increases again.
Large trees suitable for nesting, especially in southern Portugal were most pairs nest on trees, should be protected from logging. Disturbance due to recreational activities or forest work during the breeding season must be avoided.
Nests which are endangered by human disturbance or illegal killing can be guarded if enough volunteers are available.
Monitoring of all populations in Europe is important [Mebs & Schmidt 2006].
Least Concern (LC)
Status Global Raptor Information Network
Interviews about the Bonelli’s Eagle
[Bauer et al. 2005] Bauer, H.-G., Bezzel, E. & Fiedler, W. 2005. Das Kompendium der Vögel Mitteleuropas. Aula-Verlag[BirdLife International 2004] BirdLife International. 2004. Birds in Europe: population estimates, trends and conservation status. BirdLife Interntional. Cambridge, UK. (Bonelli’s Eagle species account available at: http://www.birdlife.org/datazone/species/BirdsInEuropeII/BiE2004Sp3541.pdf
[GRIN 2009] Global Raptor Information Network. 2009. Species account: Bonelli’s Eagle Aquila fasciata. Downloaded from http://www.globalraptors.org on 19 Mar. 2009
[HOS 2009] Hellenic Ornithological Society. 2009. Downloaded from http://www.ornithologiki.gr/en/oiwnos/i3/enspizae.htm on 19. Mar. 2009
[Larrey, Roger & Morvan 2007] Larrey, Frédéric & Roger, Thomas &, Morvan, Rozen. 2007. Aigle de Bonelli – méditerranéen méconnu. Regard du vivant.
[Lecacheur 2009]. Lecacheur, Marc. Interview on europeanraptors.org: Interview with Marc Lecacheur about the biology and conservation of the Bonelli’s Eagle in France.
[Mebs & Schmidt 2006] Mebs, Theodor & Schmidt, Daniel (2006). Die Greifvögel Europas, Nordafrikas und Vorderasiens. Kosmos Verlag.
[Palma 2009]. Palma, Luis. Interview on europeanraptors.org: Interview with Luis Palma about the biology and conservation of the Bonelli’s Eagle in Portugal
[SEO 2007] SEO/BirdLife Spain, Juan M. Vaerla Simó. 2007. Aves Amenazadas de España, Lynx Edicions.
Forsman, Dick (1999). The Raptors of Europe and the Middle East A Handbook of Field Identification. Poyser
Mebs, Theodor & Schmidt, Daniel (2006). Die Greifvögel Europas, Nordafrikas und Vorderasiens. Kosmos Verlag.