Eastern Imperial Eagle
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Increase number of breeding pairs
Data collection in progress
Iron Curtain to Green Belt
Bulgaria
Problem: The Iron Curtain to Green Belt region is the stronghold of the eastern imperial eagle, a globally threatened IUCN red-listed species. The breeding population of this top predator is threatened by loss of habitat, particularly nesting sites, reduced prey availability, and persecution.
Action: The creation of new treelines will secure additional long-term nesting and roosting sites for eastern imperial eagles. Protection and restoration of grassland habitat will improve availability of key small mammal prey species. Working with local communities and especially farmers, hunters and rangers to improve human-wildlife coexistence, by education, awareness and mitigation, should reduce incidences of poisoning and poaching of large eagles.
Indicator: An increasing number of breeding pairs of eastern imperial eagles and the rate of replacement of individuals within pairs inside the project area will indicate successful interventions.
Photo: Svetoslav Spasov
Photo: Georgi Gerdjikov
Methods
BSPB has a long-term annual imperial eagle monitoring programme with established methodology. As such, the location of all eastern imperial eagle nest sites in the region is already known. Each territory is visited multiple times each year to monitor all stages of the species’ life cycle:
- occupation of territory
- nest building
- incubation
- hatching
- raising of the young
- post-breeding period
The first visit to each territory takes place in February to March to determine its status and record the birds present, their age and whether either partner has been replaced since the previous breeding season. Nest repairs and/or building of a new nest are also recorded.
In March to May, visits are made to monitor the incubation process, to determine the causes if incubation is unsuccessful and to record the number of hatched young.
In June to August the territories are visited to record the number of young before they leave the nest and the number that successfully fledge. This is used to calculate the nesting and reproductive success of each pair.
Results
The baseline values were collected at the project start in 2022. Since then, 2023 data has also been collected and processed. Data from both years is presented in the table below.
In 2023 three new breeding pairs established within the project area, already achieving the project’s target number. However, these newly established pairs are formed by subadult individuals and it is still unclear whether they will stay in these new territories or will move to other areas, as often happens with pairs of immature and subadult individuals. At least two more years of monitoring will be needed to confirm that these territories are permanently occupied. This page will be updated as new annual data becomes available.
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