Searching on the edge: dynamic oceanographic features increase foraging opportunities in a small pelagic seabird

Abstract

Ocean mesoscale and submesoscale features, such as eddies and filaments, play a key role in the foraging ecology of marine predators, by concentrating nutrients and acting as aggregative structures for pelagic organisms. Highly pelagic seabirds may exploit these features to find profitable food patches in a dynamic and complex 3-dimensional spatial environment. Using miniaturized GPS loggers, we investigated whether foraging habitat selection of the Mediterranean storm petrel Hydrobates pelagicus melitensis, one of the smallest (ca. 28 g) seabirds worldwide, was affected by different static and dynamic oceanographic features during the breeding period. Individuals performed long foraging trips (up to 1113 km) in a relatively short time (1 to 2 d), covering large home ranges (up to 34370 km2), particularly during incubation. Different oceanographic features affected the at-sea distribution of storm petrels at different spatio-temporal scales. During incubation, individuals selected areas characterized by shallow waters and strong currents, conditions that may enhance vertical water mixing and increase food availability. During chick-rearing, they foraged closer to the colony, selecting shallow and productive areas, where increasing Lagrangian coherent structures and eddy kinetic energy enhanced foraging probability. These features could play an important role in storm petrels’ foraging habitat selection, especially during chick-rearing, given their need to find predictable food patches in a short timespan. Overall, our results suggest that marine circulation processes are key drivers of the at-sea distribution of this small pelagic surface predator.