Population dynamics of the Corncrake Crex crex in Slovenia in the 1992–2021 period

Abstract

Abstract The first national Corncrake Crex crex survey in Slovenia was performed in 1992/93, followed by further five in 1999, 2004, 2010, 2015 and 2020. In 2004, annual monitoring of eight most important Corncrake Natura 2000 sites (SPAs) began. Both datasets showed a moderate population decline since 1992. After Slovenia’s accession to the EU in 2004, Corncrake population steeply declined at SPA Breginjski Stol and moderately declined at SPA Dobrava - Jovsi due to scrub encroachment, whereas moderate decline at SPA Ljubljansko barje can be attributed mostly to intensive grassland management and the conversion of grasslands to arable land, resulting in nest and habitat destruction. In 2020, the number of calling males in Slovenia was smaller by 55 % compared to 1999, when the highest number ever was recorded (683). The highest average number of Corncrakes in the 1992–2021 period was counted at SPA Ljubljansko barje (139 calling males/year), whereas the smallest number was recorded at SPA Snežnik - Pivka (8 calling males/year). A comparison of target values for Corncrake population size on individual SPAs from the national Natura 2000 management programme for the 2015–2020 period with counted population sizes showed that, with the exception of SPA Lake Cerknica, all SPAs are falling behind the target values by 32–90%, depending on the site. Likewise, the majority of sites are far from reaching target values for the enrolment of agri-environmental measure VTR (first cut after 1 Aug). The article also discusses the weaknesses of current VTR, its reform in 2021, as well as other potential measures and financial sources for Corncrake conservation.