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.
Dr María Mercedes Santos (Argentina)
Dr Enrique Marschoff (Argentina)