Status and Trends in the Eastern Imperial Eagle Population Between 1977 and 2018 in Slovakia

In Slovakia, two subpopulations of the Eastern Imperial Eagle (Aquila heliaca) – Western and Eastern Slovakian – are recognized with a distance between them of 200–300 km. While monitoring of the Eastern Slovakian IE population started already in 1969, the Western subpopulation is monitored since 1977. In this study, we have evaluated trends in both subpopulations for the period 1977–2018. The reference period includes 41 nesting seasons. In total 99 breeding pairs have been recorded, which nested 1155 times in the reference period, of that 822 times successfully. As much as 1367 juveniles fledged, which makes average productivity 1.66 young per successful nest. During the reference period, the national breeding population tended to increase, and current abundance is assessed at 55–60 breeding pairs. When comparing trends in the two subpopulations, an increase in the Eastern Slovakian subpopulation was steadier, particularly in the recent years. However, breeding success was similar in the two subpopulations. About 90 % of the population was monitored, including through ringing programme and tagging with satellite transmitters. Due to the ringing programme, it became possible to record the presence of Eastern Imperial Eagle (Aquila heliaca heliaca) in Spain in 2010 and 2014, within a range of Spanish Imperial Eagle (Aquila [heliaca] adalberti).