Lake Cerknica is situated on the largest polje (karst field) in Slovenia. A temporary eutrophic lake which is usually totally dry in summer and late winter, but with an area of 2,600 ha when full in spring and autumn. There are huge expanses of reed, sedge and wet grasslands. On the eastern border of the lake, there are remnants of a raised bog. The habitats have been little affected by man. There are a few settlements along the border of the IBA, especially to the north and east, the largest being Cerknica town with 3,000 inhabitants. The lake is historically famous for its underground water system, first described in 1689.
Important numbers of the globally threatened Crex crex breed. Other species of global conservation concern that do not meet IBA criteria: Aythya nyroca (1-5 pairs, the most important breeding site in Slovenia; 10-25 birds on passage), Haliaeetus albicilla (2-5 birds feed in the area but do not breed). A total of 230 bird species have been recorded so far, of which 94 species have bred. Besides its international importance, the site has great value for nationally rare breeding species and nationally important numbers of waterbirds in winter and on passage.
BirdLife International (2020) Important Bird Areas factsheet: Lake Cerknica. Downloaded from http://www.birdlife.org on 20/10/2020.