Little Auks feed almost entirely on tiny zooplankton that are caught during wing-propelled dives. Parent Little Auks carry these zooplankton back to their chick at the colony in a throat pouch which can hold more than 15,000 individual prey items. Different zooplankton communities are associated with the different water masses in the Greenland Sea. More importantly, the energy content of individual zooplankton differs among species, with larger species generally providing more energy to predators than smaller ones. Changes in the species composition of zooplankton communities associated with changes in oceanographic conditions in the Greenland Sea will therefore directly affect the energetic value of Little Auk prey. The Little Auk's small size and relatively high-energy expenditure also make them particularly sensitive to local variability in prey. High energy demands are due to their high wing loading (low wing surface area to body size) and long foraging distances. These little birds may therefore have little ability to spend more energy on foraging if local food availability decreases. Little Auk parents may therefore only have a limited ability to buffer their chick against sub-optimal foraging conditions, and measures of chick growth and reproduction may be sensitive indicators of drastic changes in food availability.

We are comparing the breeding and feeding ecology of populations of Little Auks foraging in highly contrasted oceanographic conditions. Projects funded by the Norwegian Research Council, National Science Foundation (NSF) and Norwegian Polar Institute are studying Little Auk colonies on the west coast of Spitsbergen, and the French Polar Institute (IPEV) and NSF is funding the study of Little Auks in East Greenland. This collaborative effort officially began in 2005, with teams conducting boat-based surveys to quantify local oceanographic conditions, zooplankton availability and the distribution of feeding birds on both sides of the Greenland Sea. Teams at each study colony also collected information about how hard Little Auk parents were working, how successfully they were breeding, how fast chicks were growing and what prey species parents were feeding their chick. These data will be used to quantify the physiological and behavioural response of birds to different foraging conditions, and assess their flexibility to changes in food availability. Information gathered from both regions will ultimately allow us to model the response of Little Auk populations to predicted change in the arctic marine environment associated with climate change.