Breeding range, population size and population trend of the Ortolan Bunting Emberiza hortulana in Slovenia between 1979 and 2016

Abstract In this work we investigated the historical and present breeding range of the Ortolan Bunting in Slovenia and studied one of its last remaining breeding grounds in the country. Its range has suffered a marked decline in the last few decades, bringing the species on the brink of extinction in Slovenia. Firstly, we gathered all the available data and field records regarding the species in Slovenia and created several distribution maps outlining the status of the Ortolan Bunting in Slovenia. Thus we were able to confirm the drastic reduction in the species range, now confined to only two larger breeding grounds on the Karst (Kras). Field work was then concentrated on studying and monitoring one of the two last known populations of Ortolan Buntings in Slovenia. We paid special attention to the study of the males’ singing territories. Our main discovery was the presence of a lek in the central part of the study area, where several different male Ortolan Buntings shared their song-posts. In 2013 we counted a total of 18 Ortolan Buntings and found 5 nests, whereas in 2014 we counted 16 individuals, with 4 pairs probably breeding there. The number of breeding pairs is thus significantly lower than the total number of males holding territory. In the period from 2005 to 2016, the population of Ortolan Bunting in Slovenia was in steep decline.