As part of the LIFE TRŠCA project, we once again carried out waterbird nest surveys at Lake Cerknica. The survey period lasted from 3 April to 17 June 2026.
To minimize disturbance to breeding birds, we used a drone equipped with a thermal imaging camera and an optical zoom camera. The thermal camera enabled us to locate nests hidden within remote and dense stands of vital reedbeds that would be difficult to detect from the ground. The drone was flown at a sufficient altitude to avoid disturbing the birds. Direct human presence during the breeding season can cause birds to abandon their nests or even leave their chicks behind.
Over the course of eleven field days, we systematically surveyed six important breeding areas at Lake Cerknica:
This year's breeding season was particularly challenging for waterbirds. Compared to 2025, when exceptionally high breeding densities were recorded by Slovenian standards between 4 April and 19 July, only a small fraction of that number was recorded this year. Furthermore, almost all waterbird species experienced breeding failure, with only a single successful brood of Greylag Geese and a few Mallard broods observed.
The main reason for the poor breeding season was the highly unstable hydrological conditions at Lake Cerknica. Spring drought caused many nests to become stranded on dry ground, leaving eggs unhatched and vulnerable to predation. Although the lake refilled rapidly afterwards, most adult birds—particularly Eurasian Coots and Great Crested Grebes—had already moved to other areas. Fortunately, no large-scale re-nesting attempts occurred, as the lake unfortunately dried out again soon afterwards. Once again, nature demonstrated how closely breeding success of waterbirds depends on the lake's water regime.
As in previous years, the highest numbers of nests were recorded in the Levišča and Trščenke areas, where extensive reedbeds provide shelter from predators and human disturbance.
The most common breeding species recorded this year were:
During the surveys, we repeatedly observed the two target species of the LIFE TRŠCA project, but unfortunately breeding was not confirmed for either species this year.
Both species depend on well-preserved stands of vital reedbeds near open water and on areas free from human disturbance. Their absence as breeding species is most likely linked to unfavorable water conditions, as well as the limited availability of suitable reedbed habitat. The LIFE TRŠCA project continues to improve conditions for these and many other wetland species through habitat restoration and conservation activities at Lake Cerknica.
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.
