The Hooge Platen nature reserve is situated on intertidal and supratidal sand flats in the western part of the Western Scheldt estuary, Zeeland, separated from the mainland of Dutch Flanders by a 1 km wide channel (Fig. 1). In 1972 the first breeding bird species were Little Tern, Avocet, Kentish Plover and Oystercatcher. Until 1978 breeding success was low because of regular flooding and disturbance by tourists. In 1979 Stichting Het Zeeuwse Landschap took over the management, focusing on reducing the frequency of summer floodings, education of the public, monitoring the number of breeding birds and observations on the feeding ecology of terns. The number of breeding species increased from 4 in 1972 to 17 in 2010. In 2009 a maximum of about 7000 breeding pairs of different species were counted (Table 1). The Western Scheldt estuary is a Nature 2000 area, but also the shipping channel for the harbours of Antwerp, Gent, Vlis-singen and Terneuzen, and hence of great economic significance for both Flanders and the Dutch province of Zeeland. Intensive dredging projects in 1973,1997 and 2010 have allowed large vessels to sail to Antwerp on all tides, but have increased the tidal current and caused erosion of mudflats and sandbanks. Since 2000, numbers and breeding success of terns on the Hooge Platen fluctuate more strongly than before (Tables 1-3). It seems that food availability is the main reason. Terns feed mainly on young sandeel and herring. Sandeel arrives normally at the end of April or in early May within 1500 m distance of breeding colonies of Little Terns, and Herring between mid-May and early June. In recent years shoals of sandeel and herring have often been less common or even absent in the estuary, or arrived later in June or even July, too late for the breeding terns. In response, the terns recently seem to select breeding sites closer to the North Sea, where they are more successful. Possibly, providing artificial breeding habitat closer to the seashore may help to maintain the breeding populations.
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