NOORDHUIS R (1996) Ongoing research: Waterfowl and aquatic plants in the lakes. LIMOSA 69 (1): 26-27.

Mute Swan Cygnus olor Eurasian Coot Fulica atra Northern Pintail Anas acuta Eurasian Wigeon Anas penelope Mallard Anas platyrhynchos Bewick's Swan Cygnus bewickii

[free pdf] [dutch summary]