On the Diet and Foraging Strategy of Tundra Waders at Sivash

Abstract

Abstract The feeding on aquatic invertebrates, intensity and efficiency of forage intake were studied at the Sivash lagoons in 1995–2002 by the example of 6 wader species (217 birds). The diet composition significantly varied from seeds of plants to different species of aquatic and soil organisms. The diet at Eastern Sivash was based on Polychaeta, at Central Sivash — on Crustacea and chironomid larvae (Insecta). Foraging intensity depended on the abundance of main prey and the size of prey items taken. We distinguished the studied wader species as “probers” and “gatherers” of forage. The highest foraging intensity among “probers” and “gatherers” were observed at the Sivash lagoons in feeding sites with a high number of chironomid larvae, and the lowest one — in feeding sites with a polychaeta worm Hediste diversicolor. The wader foraging intensity was associated with high density and availability of prey items: at Central Sivash — chironomid larvae and brine shrimps (Artemia salina), at Eastern Sivash — chironomid larvae and polychaetes. Results of the stomach analysis and obtained correlations indicate a determinative role of polychaetes, molluscs, brine shrimps and chironomids in the foraging behaviour and distribution of the studied species of waders at migratory stopovers of the Azov-Black Sea Region.