Breeding is recorded in only a few core areas (maximum of 30-40 bp along river Lek and surrounding areas) and several small clusters elsewhere, all related to released or escaped birds in past decades. In several cases, breeding only started after several years of local presence. First breeding was recorded in 1977, but annually only from 1986 onwards. In 2000 at least 70-100 bp and an unknown number of non-breeders were present.
Horssen, P.W. van, Lensink, R.
- 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.