Bonelli’s Eagle

(Aquila fasciata)

The Bonelli’s Eagle is an agile hunter found in the mountainous regions of the Mediterranean, where it spends a lot of time on the wing in search for rabbits, partridges, and other prey.

Bonelli’s Eagle in flight

Due to the rarity of Bonelli’s Eagles (with just over 1000 pairs accounting for the whole European population), they have become a symbol of threatened wildlife requiring our active intervention in order to stand a chance of survival.

The best place to see Bonelli’s Eagles is Spain, which is currently home to the lion’s share of the European population of this elegant Eagle.

If you’re fortunate enough to see a Bonelli’s Eagle in the wild, it will most likely be one soaring and gliding around the mountains and ridges of the Mediterranean, while searching for rabbits and partridges on the ground below.

Bonelli’s Eagle facts

Even though it is a medium sized Eagle, the Bonelli’s Eagle maneuvers with astonishing nimbleness and speed, and is a fierce hunter that can take prey larger than itself.

Bonelli’s Eagle size

With a wingspan of up to 180 cm in females, the Bonelli’s Eagle is a large raptor, but looks smaller than other large raptors due to its slender wings and tail, which probably explain its agility.

Bonelli’s Eagle wingspan: 163-180 cm (females), 149-160 cm (males)
Length: 65-73 cm
Weight: 1,650-2,550 g

The Bonelli’s Eagle is a medium sized European eagle species, which makes it larger than a Common Buzzard, but smaller than a Golden Eagle.

Appearance

Bonelli Eagles have a light, cream-colored underside covered with brown spots, and long slender wings coupled with a relatively long tail, which allows tehm to maneuver with astonishing speed and agility.

Adult Bonelli’s Eagle perched on a rock ledge

Sexual dimorphism

Similar to other European raptors, female Bonelli Eagles are significantly larger than their male counterparts. As in other raptor species, it is thought that this provides an adaptive advantage during the breeding season, since the larger female is better at incubating and protecting young offspring.

Lifespan

A maximum age of 32 years has been documented for the Bonelli’s Eagle in the wild.

Scientific name and taxonomy

The scientific name of the Bonelli’s Eagle is Aquila fasciata. It forms a superspecies together with the African Hawk Eagle (A. spilogaster), and it is thought there are two subspecies of the Bonelli’s Eagle, only one of which is found in Europe.

The Bonelli’s Eagle used to be classified as part of the Genus Hieraaetus, but was recently reclassified as a true Eagle belonging to the Genus Aquila. Its closest relative in Europe is the Booted Eagle, which was also recently reclassified from the Genus Hieraaetus to Aquila.

Bonelli Eagle distribution

The Bonelli’s Eagle is found in a broad band surrounding the Mediterranean sea on all sides, and its range continues eastwards from the Mediterranean into the Middle East, Central Asia, and as far east as Southern China.

Bonelli’s Eagle habitat

The Bonelli’s Eagle prefers Mediterranean shrubland and open forest adjacent to mountainous regions. It avoids dense forest, but often hunts in clearings, or at the edge of forests. Outside of their breeding season, Bonelli’s Eagles can also be encountered in wetlands and marshy areas, where they hunt waterfowl.

Bonelli’s Eagle population size

The total population of Bonelli’s Eagles in Europe is estimated to be between 900 and 1,100 pairs, the majority of which reside in Spain (which has more than 700 pairs). The small size of Bonelli’s Eagle populations outside of Spain makes them more vulnerable threats than the Spanish population.

Bonellis Eagle behavior

The Bonelli’s Eagle is often seen soaring and gliding along the edges of mountains and mountainous forests, where it searches for unsuspecting prey, which is usually taken on the ground.

Feeding and diet

In the Mediterranean, rabbits and Red-legged Partridges form the largest part of the Bonellis Eagle diet. However, in addition to these species, it is known to catch a wide variety of birds, even including large species such as geese, herons, and even other birds of prey.

Breeding

The Bonelli’s Eagle predominantly nests on cliff ledges, but secondarily also builds its nest in trees. It re-uses the same nest over the years, and as a result the nest can get very large. It lays 1 to 3 eggs in February to March, and the chicks hatch after 37 to 40 days. After they hatch, the young Eagles stay in the nest for up to 70 days, and unlike other large raptors, the older chick usually doesn’t kill its younger sibling.

Migration

The Bonellis Eagle is a partial migratory species, with adult birds usually sedentary, but juveniles dispersing over large areas. This allows them to seek out areas with dense concentrations of prey, while avoiding competition with adults.

Bonelli’s Eagle conservation status

While the population of Bonelli’s Eagles in Spain (which constitutes its main breeding population) is considered stable, it is at high risk in many other parts of Europe, due to the fact that local populations consist of just a few breeding pairs.

For example, France, Italy and Cyprus each have less than 50 breeding pairs, which makes them vulnerable to additional pressures.

Threats

The main threat to Bonelli’s Eagles is electrocution on power poles, since they like to use these as perches. Since it’s possible to make power poles more safe for birds, this is a high priority for protecting the European population of Bonelli’s Eagles.