Weight loss of Antarctic Fulmars Fulmarus glacialoides during incubation and chick brooding

Weight losses incurred by incubating birds of both sexes, and weight changes at the beginning and end of shifts between successive incubation and brooding shifts were studied in the Antarctic Fulmar Fulmarus glacialoides in Adélie Land, Antarctica. The overall rate of weight loss during incubation fasts was 4.46% per day in both sexes but 3.91% per day after the first 2 days of fast once the stomach contents had been digested. Antarctic Fulmars appear to have rates of body‐weight loss significantly greater than the rates of weight loss observed in any other species of albatross or petrel. The validity of methods using the rate of weight loss to estimate incubation metabolic rates is discussed, and it appears that for birds incubating for periods of less than 2–3 days the digestion of the stomach contents can bias the estimation. The absence of change in weight at the beginning of shifts during incubation and brooding, together with the short time spent on foraging trips, suggests that food availability is high and/or food is readily accessible to Antarctic Fulmars. The availability of food allows the Antarctic Fulmar to compensate for the high energy cost of breeding that could be due to the cold Antarctic environment and perhaps also to a higher intrinsic metabolism.