A new paper, just published in Ecology, examines day-to-day variation in the energy expenditure of great cormorants Phalacrocorax carbo at the northern limit of the range, above the Arctic circle.  Using a biologging approach, we measured metabolic rate and diving behaviour every second day for a complete year. We expected these birds to have exceptionally high rates of energy expenditure, because they live in a cold environment, forage in sub-zero water, and have a partially wettable plumage.  However, contrary to this expectation, we show that great cormorants in theArctic are extremely efficient foragers and thereby minimise their foraging time and actually show very low rates of energy expenditure.