The Wadden Sea and Delta areas each hold 30-40% of the breeding population, and most of the large colonies (up to 2100 bp in 1998-2000, at Griend in the Wadden Sea). Elsewhere, important numbers are confined to the shores of Lake IJsselmeer. Breeding on the higher grounds has almost vanished since the 1970s because of vegetation succession, increased outdoor activities and heavy predation. In the lowlands, breeding in artificial habitats (colonies of up to 300 bp on flat roofs) is expanding. The population (18,000-19,500 bp in 1998-2000) never fully recovered from the crash caused by persistent pesticides in the 1960s (decrease from 30,000-40,000 bp to 5000).
- SOVON Vogelonderzoek Nederland 2002. Atlas van de Nederlandse broedvogels 1998-2000. Nederlandse Fauna 5: 1-584. Nationaal Natuurhistorisch Museum Naturalis, KNNV Uitgeverij & European Invertebrate Survey-Nederland, Leiden.