FACTORS AFFECTING DAILY ACTIVITY BUDGETS OF SOUTH-GEORGIAN SHAGS DURING CHICK REARING AT BIRD ISLAND, SOUTH-GEORGIA

Radio telemetry was used to record daily activity budgets of 26 South Georgian Shags (Phalacrocorax georgianus) during the chick-rearing per iod at Bird Island, South Georgia. There was a significant sex differe nce in the timing of feeding, with the female making the first trip of the day in 93% of pairs (n = 15). On average, each shag made 2.3 trip s/day and was absent for a total of 6.22 hr/day. The majority of time away from the colony was spent diving (86.7%), but long recovery perio ds on the surface between dives and time needed to travel to the seabe d resulted in only 1.06 hr/day being potentially available for prey ca pture. Given that these activity data were collected during a season w hen feeding conditions were favorable, breeding shags at Bird Island a ppear to have little capacity to increase the time available for prey capture. We speculate that the population may be extremely sensitive t o changes in food availability. Males spent more time flying and on th e sea than did females. On average, birds with broods of two or three chicks spent more time diving (6.42 hr/day) than those with broods of one (4.74 hr/day) but there was no tendency for the amount of time spe nt diving to increase with chick age. Although South Georgian Shags ex hibited the same sexually distinct foraging patterns as Antarctic Shag s P. bransfieldensis at a colony on the Antarctic Peninsula, their act ivity budgets differed radically, with shags at Bird Island spending a much greater percentage of their time away diving (86.7% compared wit h 8.4%).