Marine distribution and foraging behaviour of European storm-petrels in relation to predation risk, competition and oceanography

Little is known about the behaviour of very small seabirds at sea, largely due to the practical constraints in tracking them remotely; however, GPS tags are now miniaturised enough to track birds as small as the European storm-petrel Hydrobates pelagicus (~26 g). We examined the marine distribution of 28 European storm-petrels on 43 journeys from their breeding colony on Mousa, Shetland, UK. We first compared the observed locations of storm-petrels with a random set of locations matched by distance from the colony. We found that predators, conspecifics, wind and oceanographic variables were important influences on the distribution of storm-petrels. The presence of storm-petrels from the Mousa colony was negatively associated with the predicted abundance of storm-petrels from other colonies, indicating spatial segregation. Presence was also significantly higher at locations with intermediate wind speeds (4-8 m s -1 ), cooler sea surface temperatures (