Field metabolic rates of black-browed albatrosses Thalassarche melanophrys during the incubation stage

Field metabolic rates (FMR) and activity patterns of black-browed albatrosses Thalassarche melanophrys were measured while at sea and on nest during the incubation stage at Kerguelen Island, southwestern Indian Ocean. Activity-specific metabolic rates of five albatrosses at sea (FMRat-sea) were measured using doubly labeled water (DLW), and by equipping birds with wet-dry activity data loggers that determined when birds were in flight or on the water. The metabolic rates of four birds incubating their eggs (FMRon-nest) were also measured using DLW. The mean9/SD FMRat-sea of albatrosses was 6119/96 kJ kg 1 d 1 compared to FMRon-nest of 1969/52 kJ kg 1 d . While at sea, albatrosses spent 52.99/8.2% (N /3) of their time in flight and they landed on the water 41.29/13.9 times per day. The FMR of blackbrowed albatrosses appear to be intermediate to that of three other albatross species. Based on at-sea activity, the power requirement of flight was estimated to be 8.7 W kg 1 (or 4.0 /predicted BMR), which is high compared to other albatross species, but may be explained by the high activity levels of the birds when at sea. The FMRat-sea of albatrosses, when scaled with body mass, are lower than other seabirds of similar body size, which probably reflects the economical nature of their soaring flight.