Imperial Eagle (Aquila heliaca)
The (eastern) imperial eagle is a large eagle breeding from central and south-eastern Europe to central Asia. It is a lowland species that has been pushed to higher altitudes by persecution and habitat loss. In central and eastern Europe, it breeds in forests at altitudes of up to 1,000 m asl, and also in steppe and agricultural areas with large trees. In Bulgaria its nests are often situated in groups of trees within river valleys in hilly areas.
The European breeding population of the imperial eagle is very small (possibly as low as 850 pairs). It declined substantially during the period 1970–1990, and is probably still declining. The main threats to the species are destruction and alteration of breeding and feeding habitats, nest robbing and illegal trade, shooting, poisoning, shortages of prey species (particularly European souslik Spermophilus citellus), electrocution by powerlines and human disturbance of breeding sites. The only place where the imperial eagle population has increased significantly in recent years is the Carpathian basin, and in particular the part of this basin lying within Hungary and Slovakia. This increase has largely been due to the implementation of intensive conservation measures during two LIFE projects. The present project aims to replicate the success of these projects in Bulgaria, where there has been a gradual increase in the number of occupied nests and successfully fledged juveniles due to the active application of special conservation measures over the last decade.
The project will cover all key SPAs for the imperial eagle in Bulgaria, containing 17 of the 20 known occupied nests in the country. It is important to note that the selection of the project SPAs was based on the latest (2007) data on the imperial eagle’s breeding localities. Of the 20 known nest sites, 17 are located in the Sakar, Western Strandja, Sredna Gora, Sinite Kamani-Grebenets and Arda Bridge SPAs; the remaining three are located within 15 km of these SPAs. Although these are all of the nest sites that are known to have been occupied in Bulgaria in recent years (2005-2007), the total national population is estimated to be 25-30 pairs (Stoychev et al., in press). Other SPAs included in the project – namely the Central Balkan and Ponor SPAs – are believed to hold 2-4 pairs, although the nest sites of these pairs remain unknown. Thus, more than 80% of the national breeding population of the imperial eagle will be covered by the project. Moreover, the Kamenski Bair and Besaparski Hills SPAs – which are also included in the project – are of particular importance as foraging areas for this species.
In Bulgaria, some adult imperial eagles remain within their breeding areas all year round – especially those in the southernmost parts of the country. Therefore, the nesting and wintering sites of these birds overlap to some extent. Other adult birds probably leave their nesting areas, but little is known about where they go. Even fewer data exist about the dispersal and staging areas of juvenile imperial eagles. Given the critical importance of the first months of independent life for the survival of these birds, information about juvenile dispersal would be extremely valuable in informing successful conservation measures.
Although the imperial eagle is strictly protected in Bulgaria, being listed on Annexes 2 and 3 of the Act on Biological Diversity, its real conservation status needs improvement. This is because, even within SPAs, nesting sites face a number of threats related to increasing development, insufficient law enforcement and other factors.