Distribution, Abundance and Breeding Performance of Lesser Spotted Eagle Clanga pomarina Brehm, 1831 (Ayes: Accipitridae) in Southeast Bulgaria

摘要

The Lesser Spotted Eagle Clanga pomarina Brehm, 1831 is a long-lived, territorial raptor, distributed mainly in Eastern and Central Europe. Southeast Bulgaria is a part of the southern limit of the species distribution range. During the period 2014-2018, 76 active nests were found and 173 occupied territories were mapped in Southeast Bulgaria. About 60% of the breeding population of the Lesser Spotted Eagle in this region was situated in Special Protected Areas but only 2.3% was located within reserves. The highest breeding density was recorded in the Dervent Heights - western foothills of the Strandzha Mnt., while the lowest breeding density values were established in the central part of the Strandzha Mnt. The measured nearest neighbour distance ranged from 0.68 km to 4.5 km, at a mean value of 2.43 km +/- 1.16. The average productivity was 0.5, average breeding success 0.67, and average breeding frequency 0.74. Higher values of productivity were reported for the Strandzha Mnt. and the Harmanliyska River and lower productivity was recorded in the Byala Reka catchment area with no significant differences between the regions. In general, the population of the species in Southeast Bulgaria was stable, with a possible slight increase in the Sakar Mnt. and the Dervent Heights and a decline only in the Strandzha Mnt. The Lesser Spotted Eagle population breeding in the country had been significantly underestimated. The increasing anthropogenic pressure, mainly in terms of dramatic alteration of the species foraging and breeding habitats, and the lack of efficient legal protection, pose a serious risk to the future of the Lesser Spotted Eagle in this part of the species distribution range.