Herring Gull Larus argentatus winter diet at the western Baltic Sea coast: does ice cover make a difference?

The diet of Herring Gulls Larus argentatus at Kiel Fjord, Baltic Sea, was assessed from pellets collected in a very cold winter (1995-96), in a very mild winter (1997-98) and in spring 1996 for comparison. Bivalves (mainly Mytilus were the most frequently occurring food item in all three periods. Gastropods (chiefly Littorina spec.) and crustaceans (mainly Carcinus maenas) were following next. Stones and different types of plant material were also quite frequently present in the pellets. Differences between the three periods were not very marked. Crustaceans, algae, grass and stones were most abundantly found in the cold winter. Oligochaetes occurred only in spring. Stones were quite common in the pellets both by frequency and by mass. In the cold winter 1996, mean stone mass comprised 47% of total pellet mass. It is concluded that Herring Gulls did not alter their diet in the cold winter to a major extent.