The breeding distribution, never mapped before, focuses on urban areas, where the species is much more numerous than Mallard. In farmland, densities are highest in the lowlands, especially in the province of Friesland, where local organisations stimulated the use of special nestboxes. Although an increase in numbers and distribution in recent decades is likely, hard evidence is almost lacking. Population numbers are poorly known. Extrapolating regional densities there might be some 35,000-60,000 bp.
- 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.