Frank D. (1992) The influence of feeding conditions on food provisioning of chicks in Common Terns Sterna hirundo nesting in the German Wadden Sea. ARDEA 80 (1): 45-55

Feeding conditions and food provisioning of chicks were studied in three Common Tern Sterna hirundo colonies in the Jade Bay, German Wadden Sea, from 1984 up to and including 1986. Two colonies were situated on the mainland coast, one was situated on an island. Differences in diet between years and colonies based on analyses of pellets, food items dropped near nests and film recordings paralleled differences in prey stock as revealed from drag-net catches in the birds' foraging areas. Food fed to the chicks in the island colony comprised almost exclusively of marine prey items. In the mainland colonies, however, three-spined sticklebacks Gasterosteus aculeatus were prevalent. Species composition of fish varied with wind speed on the island and with the stage of the tidal cycle both on the island and on the mainland coast. Chick-feeding rates also varied considerably between years and between sites, and with wind speed and with the stage of the tidal cycle. Because terns nesting on the mainland coast switched to inland waters to forage as soon as foraging conditions in the Wadden Sea became worse, the general food situation for these terns was better than for those nesting on the island.