A new scientific publication by leading experts from the Bulgarian Society for the Protection of Birds (BSPB) presents the results of a 10-year study on the breeding performance of the Lesser Spotted Eagle (Clanga pomarina) population in Bulgaria.
Based on data collected between 2015 and 2024 from 479 monitored territories, the study found no long-term trends in productivity, breeding success, or breeding frequency – clear evidence of a “spatially consistent” breeding performance along the southern periphery of the species’ range. However, the territory occupancy rate showed a slight decline over time, most pronounced in the Sakar Mountain region.
The primary drivers of this decline are rapid and large-scale landscape changes – conversion of grasslands into intensive cropland, removal of shrub vegetation, prolonged droughts, and large wildfires. Interactions with larger raptors may also be contributing negatively. These factors degrade both breeding and foraging habitats and may be exacerbated by climate change if urgent conservation actions are not implemented.
© Dimitar Plachiyski/BSPB
The study also examined the effect of breeding density. In territories with medium breeding density, the species showed the highest productivity, while in high-density areas, the likelihood of initiating breeding in poor years was lower. This suggests that habitat quality and competition play a significant role in the eagles’ decision whether or not to breed in a given year.
Among the recommended conservation measures outlined in the paper are:
- Establishing an early-warning and rapid-response system for wildfires;
- Maintaining small water reservoirs that support both fire suppression and prey availability;
- Replacing old, fire-prone conifer plantations with resilient native broadleaved species, particularly oak;
- Restoring a mosaic of permanent grasslands and hedgerows in agricultural landscapes.
The integration of these measures into forest and land-use planning is considered critical.
The study was conducted with the support of the LIFE projects “Eagle’s Forests” (LIFE12 NAT/BG/001218) and “LIFE for Eagle’s Habitats” (LIFE18 NAT/BG/001051).
You can read the full paper here: Temporally Determinate, but Spatially Consistent Breeding Performance of Lesser Spotted Eagle (Clanga pomarina) Along the Southern Periphery of Its Distribution.