Acrocephalus 40 (180/181): 55–67, 2019 10.1515/acro-2019-0003 Area use and important areas for Common Tern Sterna hirundo inland populations breeding in Slovenia and Croatia Raba območij in pomembna območja celinske populacije navadne čigre Sterna hirundo v Sloveniji in na Hrvaškem v času gnezdenja Davorin Tome 1, Miloš Martinović2, Jelena Kralj2, Luka Božič3, Tilen Basle3, Luka Jurinović4 1 Nacionalni inštitut za biologijo, Večna pot 111, SI-1000, Slovenia, e-mail:
[email protected] 2 Hrvatska akademija znanosti i umjetnosti, Zavod za ornitologiju, Gundulićeva 24, 10000 Zagreb, Croatia, e-mail:
[email protected],
[email protected] 3 DOPPS – BirdLife Slovenia, Tržaška cesta 2, SI-1000 Ljubljana, Slovenia, e-mail:
[email protected], tilen.
[email protected] 4 Hrvatski veterinarski institut, Centar za peradarstvo, Heinzelova 55, 10000 Zagreb, Croatia, e-mail: luka.
[email protected] During the breeding periods of 2018 and 2019 we investigated the extent of areas Common Terns Sterna hirundo use while searching for food. We used GPS-UHF tags to follow the movements of 23 terns from Slovenia (7 individuals) and Croatia (16 individuals). We investigated the movements of birds from three breeding sites, i.e. Lakes Ptuj, Siromaja 2 and Rakitje. Conclusions are based on 43,105 locations which were collected with a frequency of one reading per 20 minutes during the day and one reading per 4 hours during the night. In Slovenia, terns used a 60 km long and narrow area over Stara struga Drave (former river-bed of the Drava River) between Ormož and Maribor as well as eleven fishponds / lakes in its surroundings, most of them in the Pesnica valley.