Foraging patterns in the Antarctic Shag Phalacrocorax bransfieldensis at Harmony Point, Antarctica

During the 1995 and 1996 summer seasons the foraging patterns of the Antarctic Shag Phalacrocorax bransfieldensis were studied by direct observation on individuals breeding at Harmony Point, Nelson Island, South Shetland Islands. During pre-laying and incubation individuals of both sexes usually foraged once a day, females early in the morning and males when their partners returned to their nests. Compared to  those periods, when rearing chicks parents incremented the number of daily foraging  trips, usually alternating the time at sea, and reduced their duration. Rearing individuals  responded to increasing energy requirements at the nests (i.e. as chicks grew older or at  increasing number of chicks at the nests) by incrementing the number of daily foraging  trips and the daily time invested in foraging activities. The information obtained suggests  that Antarctic shags invest time in activities which lead them buffer variable food  abundance or energy requirements at the nests. The possibility of using the foraging  parameters considered in this study in ecosystem monitoring programmes is discussed.