(33rd Publication of the Vogeltrekstation Foundation) The steady increase of the human population with all its consequences is an omnipresent threat to the wildlife of the Netherlands, especially to the larger animals who make greater demands on their habitat. That is why preservationists must continuously watch that the living conditions of such species do not drop below a certain level. Besides the various reclamation works and reallotment schemes that have been carried out all over the country, the huge hydraulic-engineering works, known as the "Delta Plan" in the provinces of Zuid-Holland and Zeeland will probably prove to have a really serious effect on the birds that are in the habit of feeding in tidal waters. For these hydraulic works will close off the estuaries of the Rhine and the Meuse, thus bringing an end to the tides which provide not only rich feeding opportunities but also safety (by making the habitat more or less inaccessible to men). Among the birds frequenting these tidal waters the Spoonbill is perhaps the most precious one. Hence, as regards its favourite feeding grounds the prospects for this species — chosen as our "national bird" in 1962 — are rather unfavourable. These prospects, together with the fact that our Spoonbill population has shown a decrease since 1950-1954, lead me to the subject of this paper. Although it is mainly based on literature, the first two chapters contain many of my own observations; I am indebted to Mr. C. van Orden for some recent data on the Zwanenwater and Texel colonies. Furthermore I want to thank Dr. A. C. Perdeck and his staff of the "Vogeltrekstation Foundation" for the kind assistance in providing me with the most recent ringing records, and Prof. K. H. Voous for help with literature.