Mainly concentrated at the Wadden Sea islands, elsewhere only small numbers breeding on the mainland coast of Friesland and Groningen and in the Delta. Breeding numbers are difficult to assess because of census problems, but it is obvious that the main colonies on Vlieland, Terschelling and Schiermonnikoog hold 2000-3500 bp each. About 87% of the international Wadden Sea population breeds in the Dutch part of the area. Only minor distributional changes occurred since the 1970s. A substantial increase in numbers (4000 bp in 1976, 8000-10,000 in 1998-2000) has recently levelled off. A future decline is likely, as the birds are faced with depleted food stocks (mussels and cockles) caused by human over-exploitation.
Vergeer, J.-W., Dijksen, L.