Diving behaviour differs between incubating and brooding Brunnich's guillemots, Uria lomvia

Bird-borne data loggers were used to investigate the foraging strategies of Brunnich's guillemots breeding in a colony in the North Water Polynya: the flight performance and diving activity of incubating birds were compared to those of chick-rearing individuals. No significant differences were recorded between the bird groups in the potential foraging range. Conversely, clear differences were revealed between incubating and chick-rearing birds in diving behaviour. Chick-rearing birds were generally foraging at a significantly greater depth, and spent significantly higher proportions of the time submerged, than brooding individuals. Despite these differences, the estimated average daily energy expenditure of chick-rearing Brunnich's guillemots was only about 6% higher than that during incubation.