Although the species is not easy to census (underestimate likely in optimal habitat, overestimate in marginal habitat), it is clear that the actual breeding distribution is mainly confined to lowland deciduous forests including poplar plantations. On the higher soils, the species lost much of its breeding area since the 1970s. The thriving population in new forestry plantations in Flevoland has been reduced markedly since the early 1990s as well. Some 4000-5000 bp in 1998-2000 (7000-10,000 in 1979-85).
Diermen, J. van
- 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.