FOOD AND FEEDING ECOLOGY OF PURPLE SANDPIPERS CALIDRIS-MARITIMA ON ROCKY INTERTIDAL HABITATS (HELGOLAND, GERMAN BIGHT)

On the island of Helgoland (German Bight) Purple Sandpipers Calidris m aritima feed mainly in the intertidal of piers and rocky shores. The m ain prey species are Littorina saxatilis and Mytilus edulis, complemen ted by crustaceans, polychaetes, other molluscs and green algae. Beach habitats are used as alternative feeding sites during storms. Feeding sites seem to be selected according to rates of assimilated energy in take. The most profitable habitat (wrack beds on the high-tide line wi th kelp-fly larvae, 16.8 W) is used after arrival in October but is no t available during winter. Because of high intake rates in rocky habit ats (13.1 W on piers, 5.5 W on mussel beds), which allow short daily f eeding times, and available alternative feeding sites during storms, P urple Sandpipers do not need to carry fat reserves in winter like othe r waders wintering in central and western Europe. This, and the ever a ccessible food supply of epibenthic macrofauna on rocky shores, may en able Purple Sandpipers to winter further north than other wader specie s.