As part of the LIFE TRŠCA project, we conducted a survey of waterbird nesting within the area of Lake Cerknica. The survey took place during the spring and early summer, from April 3rd to July 4, 2025.
To observe the birds in the least invasive way possible, we used an unmanned aerial vehicle (drone) equipped with a thermal camera and a zoom lens. The drone flew at a high enough altitude to avoid disturbing the birds. The thermal camera enabled us to locate nests in remote and densely vegetated reedbed stands. We detected nests and birds by identifying thermal contrasts, and the zoom camera allowed us to determine species and assess nest conditions – all without entering the sensitive reedbed areas where many waterbird species nest. Human presence during the breeding season often leads to nest abandonment or even the desertion of chicks.
We carried out a total of 19 fieldwork days and systematically surveyed six key areas of the intermittent lake. Based on partial data analysis, the results are as follows:
- Beli breg (57 ha): 49 nests
- Ključi (74 ha): 118 nests
- Levišča (53 ha): 214 nests
- Trščenke (126 ha): 201 nests
- Zadnji kraj (26 ha): 18 nests
- Žerovniščica (56 ha): 83 nests
In total, we recorded 683 nesting structures, confirming the exceptional importance of Lake Cerknica as a key breeding habitat for numerous waterbird species.
The largest number of nests was recorded in the areas Levišča and Trščenke, which also have the largest contiguous reedbeds. These provide birds with adequate protection from predators and human disturbance. Levišča, in particular, stands out with extremely high densities, more than twice that of other areas.
Among the most commonly nesting species this year were:
- Eurasian Coot (Fulica atra) – a robust and adaptable species, often nesting in both dense and moderately sparse reedbeds.
- Great Crested Grebe (Podiceps cristatus) – an elegant species known for its courtship displays, which builds floating nests.
Although we frequently recorded target species, we did not detect nests of the two key target species of the LIFE TRSCA project:
- Ferruginous Duck (Aythya nyroca) – a threatened species of duck with declining populations in Europe
- Red-necked Grebe (Podiceps grisegena) – a rare and sensitive grebe species
Both species depend on vital reedbed stands located near open water and undisturbed by human presence. Their absence is likely due to the lack of sufficient stands of vital reedbeds.
The attached image provides a map-based representation of the surveyed areas and the number of nests recorded in each. These data will serve as a baseline for long-term monitoring of breeding success and habitat quality. Moreover, they will support timely planning of conservation measures for species that rely on stable conditions and undisturbed environments during their breeding season.
Lake Cerknica is not only the largest intermittent lake in Europe but also a vital bird area included in the Natura 2000 network. Regular survey of waterbird populations enables us to assess the impact of human activities, land use changes, and climate change – and to respond in time.
The LIFE TRŠCA project, through such activities, significantly contributes to the conservation of wetland biodiversity and the protection of birds that increasingly depend on our responsibility and knowledge.
The implementation of extensive nature conservation projects exceeds the financial capacity of the local community, therefore Notranjska Park regularly applies for projects with the possibility of co-financing by the European Union.
The implementation of large-scale conservation projects exceeds the financial capabilities of the local community, therefore Notranjska Park regularly applies for projects with the possibility of co-financing from the European Union.
