The challenges of bird conservation on an intermittent karst lake: The interplay between changing water level and agriculture

Abstract

1. Intermittent karst lakes are important for forming wetland habitats in otherwise dry karstic landscapes. With characteristic water regimes they are unable to retain water owing to their underground drainage system. 2. Many Dinaric intermittent karst lakes (karst poljes) have gone through severe human disturbances in the past, aimed at fluctuating water levels in karst poljes. These measures had the goal of achieving either permanent dry agricultural land or permanent lakes for various purposes. Usually dams were built for water storage to achieve these goals. 3. This research aimed to determine the population responses of bird species that are important for conservation, to water level changes on Cerknica Lake (Slovenia), a large Dinaric intermittent karst lake, to inform effective conservation for such systems. 4. Water level and vegetation were strong drivers of waterbird diversity and abundance, based on analysis using canonical correspondence analysis and boosted regression trees. 5. Water level was critical for the conservation of important bird species. Water and reed specialists (e.g. water rail Rallus aquaticus) require management of refugia in wetlands to create mosaics of water and reedbeds. The formation of nature reserves, quiet zones and habitat restoration is needed for these specialist species. In these areas, mowing should be limited or not present at all. 6. Measures dealing with land-use change and connectivity between habitats, for instance agri-environmental measures, are more appropriate for rare bird species with wider niche breadths (but still narrower than generalists), e.g. skylark (Alauda arvensis) and linnet (Linaria cannabina).