The breeding distribution is directly related to released birds or escapes, including some major concentrations (150 bp near Purmerend, north of Amsterdam). In 1973-77 only a few breeding pairs were reported, and breeding was often prevented by shooting. A steady increase, by about 10% per year, in the 1980s and 1990s, resulted in 1000-1400 bp in 2000. Recently, the growth rate of the breeding population tends to increase. Therefore, a further range expansion is likely.
- 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.