De relatie tussen het gebruik van de zeereep door stormmeeuwen Larus canus en het voorkomen van vissende meeuwengroepen op zee

In this paper the occurrence of mass-feedings of gulls at sea (<1-6 km from the coast), is compared with Common Gull activity along the coast. Numbers flying along the coast (seawatching results) were compared with numbers flying over the dunes (counted for this project) in table 1, when there were, or were not, mass-feedings of gulls at sea. The daily pattern of gulls flying along the coast and over the dunes was very similar (figure 1). Numbers flying over the dunes and over the sea increased dramatically when mass-feedings were present. Common Gulls, other than Herring and Lesser Black-backed Gulls, were found to fly straight to the mass-feeding rather than along the coast first and then towards the feeding flock (figure 2). Massfeedings of gulls at sea in summer are a well known feature. The gulls are feeding on Sprat or sandeels, particularly when these fish are near the surface, pursued by Mackerel. In the chick rearing period of Common Gulls, fish is an important item in their diet. The gulls soaring over the dunes were apparently awaiting the development of a mass-feeding. When a mass-feeding was observed, Common Gulls took the shortest way, rather than the ’cheapest’ route (soaring over the dunes costs very little energy); obviously to arrive in time to get their share, before the more powerful Herring and Lesser Black-backed Gulls arrived.