Dispersal of eastern imperial eagles from the Czech Republic

Abstract. The first successful breeding of eastern imperial eagles (Aquila heliaca) in the Czech Republic, which lies at the north-western edge of its world breeding range, was confirmed in 1998. Here we summarise the dispersal, overwintering and expansion of the Czech population based on observational, ringing and telemetry data. The Czech breeding population had increased to at least 14 breeding pairs and 18 territorial pairs by 2022. Between 2017 and 2021, 19 nestlings were equipped with GPS/GSM devices. Two of the 16 surviving individuals (12.5%) spent their first winter in the Mediterranean (1,460 km and 1,671 km from natal nest), but did not repeat this migration pattern again. The other 14 tracked individuals wintered close to their natal areas. Maximal recorded distances from the natal nest and total area occupied (100% minimal convex polygons) were significantly lower in the first calendar year than the second. Signs of settlement prior to the first nesting attempt were already apparent by the third or fourth calendar year. Excluding exploratory trips during the floater period, final natal dispersals for two of the breeding males were 46 km and 92 km, respectively. Further spreading of the species' Czech breeding range is expected in the future.