Breeding is confined to large marshes (Flevoland, Lake IJsselmeer, Border Lakes and Lauwersmeer) with scattered populations elsewhere, e.g. at some Wadden Sea islands and brackish estuaries like Dollard and Saeftinge. The distribution is probably slightly overestimated since the species is difficult to assess and population fluctuates from year to year. Only seven areas hold over 25 bp, of which Oostvaardersplassen (max. 640 bp in 1998-2000) is clearly the most important. The population decreased steeply in the past decades, mainly as a result of the cultivation of Zuidelijk Flevoland, where numbers dropped from 7000 bp in 1973-77 to 300-800 in 1998-2000. At the same time, however, some expansion to other sites was recorded and numbers here rose from 500-1000 to 800-1200 bp. The Dutch population in 1998-2000 is estimated at 1200-2000 bp.
- SOVON Vogelonderzoek Nederland 2002. Atlas van de Nederlandse broedvogels 1998-20005: 1-584. Nationaal Natuurhistorisch Museum Naturalis, KNNV Uitgeverij & European Invertebrate Survey-Nederland, Leiden.