Temporally Determinate, but Spatially Consistent Breeding Performance of Lesser Spotted Eagle (Clanga pomarina) Along the Southern Periphery of Its Distribution

Breeding performance encompasses offspring production, their survival rate, fertility, overall reproductive outcome, timing of reproduction, and breeding frequency. It varies in raptor species, being affected by different biotic, abiotic, and anthropogenic factors. The Lesser Spotted Eagle is a monogamous, long-lived, slowly reproducing raptor, characterized by site-fidelity and strongly territorial behavior. In this study, we examined data collected over a 10-year period, highlighting the eagles’ main breeding parameters, analyzing whether any of them demonstrated significant trends or spatial or temporal differences over the study period. We also searched for a strict correlation between species breeding density and breeding performance. We found out that the mean occupancy rate of the territories marginally decreased β2 = −0.64 ± 0.27, p = 0.047, as this process was clearly visible in Sakar Mnt. (β2 = −0.66 ± 0.27, p = 0.038), where in 2022, only 67% of the monitored territories were occupied. The overall mean productivity, breeding success, and breeding frequency did not indicate any trend over the years (p > 0.05). Of all tested breeding parameters, occupancy rate (β2 = 0.29 ± 0.14, p = 0.04) and breeding success (β2 = −0.12 ± 0.06, p = 0.04) varied yearly, while productivity (β2 = 0.25 ± 0.12, p = 0.03) and breeding frequency (β2 = 0.27 ± 0.12, p = 0.03) were influenced by density. None of the tested indicators demonstrated significant regional differences, which indicated a temporally determinate, but spatially consistent pattern of breeding performance of the species in this part of its distribution. Recently, the landscape pattern in the south-eastern part of the country was marked by spectacular habitat loss, driven by human activities and natural phenomena, with entire biodiversity facing an uncertain future. Prompt action and urgent decisions are needed to prevent the negative consequences of these imminent threats to the species. Conservation efforts should be focused on the restoration of breeding and foraging habitats. Further research on the response of eagles to the effect of natural (fires) and anthropogenic (habitat transformation) factors, as well as the relationship between breeding performance and different drivers of reproduction, such as diet, weather, habitat features, and presence of intra- and interspecific competitors, would be of crucial significance.