Data sources

1. Davidson, N.C. & T. Piersma (eds.) 1992 The migration of Knots. Wader Study Group Bulletin 68. Specisl issue

2. del Hoyo, J., Elliot, A. & J. Sargatal (eds.) (1996): Handbook of the Birds of the World.Vol. 3 Hoatzins to Auks. Lynx. Barcelona. 821 p.

3. Rose, P. & D. Scott (1997): Waterfowl population estimates. Welands International Publ. 44. 106 p.