Successful colonisation of The Netherlands, initiated by escapes, took place from 1967 onwards. The initial centres of expansion were located near The Hague in the west of the country (first breeding in 1967), in the eastern river area (1977) and around the city of Groningen in the northeast (1981). Actual densities in lower grassland areas often amount to 5-10 bp/100 ha, with much lower figures on arable land and on the pleistocene soils. The national population increased from 1 bp in 1967 to 48 in 1977, 345 in 1989 and 4500-5000 in 1998-2000.
- 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.