​September – Month of the Imperial Eagle

We dedicate September to the “master of storms” – the Imperial Eagle!
Description of the species
The Imperial Eagle (Aquila heliaca Savigny, 1809) is one of the largest eagles in Bulgaria. Its body reaches up to 72-84 cm with 180-215 cm wingspan. The female is usually larger than the male – with males up to 2.4-2.7 kg while females reach 3.1-4.5 kg. Adults have dark brown plumage with two white spots on the shoulders and golden coloration of the neck. The tail is relatively shorter than the tail of the Golden Eagle (Aquila chrysaetos) with a gray base. Young birds have a light brown coloration and dark flight feathers (Cramp & Simmons 1980).

According to literature, at the end of the 19th century there were 1 824 breeding pairs in Bulgaria (Petrov et al. 1996). The Imperial Eagle was one of the most common birds, preferring to nest on single large trees in the middle of fields, near settlements. Today, the population of the Imperial Eagle is estimated at about 25-30 pairs (Demerdzhiev et al. 2011), with only 18 sure nesting pairs in 2008. In 2020 only 34 pairs of Imperial Eagles were found.
These alarmingly low numbers determine the conservation status of the Imperial Eagle.
Over 90% of the population of the Imperial Eagle in Bulgaria is concentrated in the region of the Sakar Mountain and Derventski Vazvishenia (Heights). These areas have become the last strongholds of these majestic and beautiful birds.
The main threats that have brought the species to the brink of extinction are similar to those for other birds of prey - the loss of nesting and hunting habitats, poaching, poisonous baits, electrocution and collisions with powerlines, human disturbance, robbery of nests and illegal trade.
The Imperial Eagle is a monogamous species. It reaches sexual maturity at the age of 4. The pair is strongly attached to the nesting area, with some nesting sites occupied by the same pair for many years. The mating behavior starts in February and is most intense in March. It consists of birds rising in the air with a sharp dive with folded wings followed by another rapid rise.
They build large nests with sticks usually on top of trees or electric poles. The Imperial Eagle prefers single tall trees, growing alone or among strips of vegetation along rivers, in shallow valleys, as well as groups of trees at the edge of forests or near meadows, often near settlements, roads and arable land.
Nests are mostly located on trees usually between 7 to 26 m from the ground and are built by both birds. They are made of dry branches and reach 120 to 220 cm in diameter and 30 to 90 cm in thickness. Nests are usually inhabited only in spring and summer. The clutch consists of 2, less often of 1 or 3 eggs. Both birds take part in the incubation which lasts about 43 days. The chicks leave the nest after the second half of July and the beginning of August. For a while, they return to spend the night in it or stay around, while their parents continue to feed them. The birds remain in their nesting area until the second half of September – the end of October.
Conservation measures
The Green Balkans work for the monitoring, research and conservation of the Imperial Eagle in Bulgaria dates back to the 80’s with the observation of the first two breeding pairs for the Sakar region. This was followed by a series of studies and regular monitoring of all known nests, expeditions to locate new Imperial Eagle nests, study of suitable nesting areas and determination of limiting factors.
Conservation activities include:
  • Protection and monitoring of nests during the breeding period in order to prevent the robbery of eggs and chicks from poachers, disturbance of the birds, or cutting down trees on which nests are located. The observations help to provide valuable scientific information about the behavior and ecology of the species, which are of great importance for its conservation.
  • Afforestation contributes to overcoming one of the main limiting factors for the spread of the species - the lack of suitable trees for nesting. Experience from other countries shows that artificial nests contribute to the attraction of birds and raise the nesting chances in a given area;
  • Marking of individuals with colored rings, radio and GPS transmitters to track the movement and migration of Imperial Eagles;
  • Conducting research on the food spectrum, biology, behavior and ecology of the species;
  • Educational campaigns with local people - raising the ecological culture of people in the areas where the species occurs is extremely important for its conservation. Green Balkans holds numerous meetings and presentations with local people, town halls and schools for the protection of the Imperial Eagle;
  • Proper management and conservation of Imperial Eagle habitats - the maintenance of pastures in areas where the species occurs is crucial for its conservation, as well as for the conservation of other rare species such as the souslik (Spermophilus citellus), which is an important food resource for all diurnal birds of prey (Golemanski et al. 2011). The support of local farmers is another good example of cooperation between environmental organizations, agriculture and business for the benefit of biodiversity.
  • Rescue of distressed Imperial Eagles and subsequent treatment and rehabilitation at the Green Balkans Wildlife Rescue Center.

The species is also part of the breeding program for rare species
In the IUCN (International Union for Conservation of Nature) list, the species is in the category Vulnerable (IUCN 2018). It is included in Annex II of the CITES Convention (Convention on International Trade in Endangered Species of Wild Fauna and Flora), in Annex II of the Bern Convention (Convention on the Conservation of European Wildlife and Natural Habitats) and in Annex II to the Bonn Convention (Convention on the Conservation of Migratory Species of Wild Animals), in Annex I of the Birds Directive.
In Bulgaria it is in the category Critically Endangered (Golemanski et al. 2011), listed in Annex II and III of the Biodiversity Act.
How can I help
Contact us:
Gradimir Gradev - Conservation Department Expert
mobile phone: +359885 609289; e-mail: ggradev@greenbalkans.org
Green Balkans Head office - Plovdiv
tel .: 032/62 69 77, 032/62 69 15; e-mail: office@greenbalkans.org
Wildlife Rescue Center - Stara Zagora
phone and fax: (042) 60 77 41; mobile phone: +359886/570053
Green Balkans
Hobby Tv
Natura 2000