Flight destinations and foraging behaviour of northern gannets (Sula bassana) preying on a small forage fish in a low-Arctic ecosystem

We applied data loggers (temperature-depth and GPS-temperature-depth) on individual birds in combination with dietary sampling and a vessel survey of prey availability to assess the foraging behaviour of northern gannets (Sula bassana, Linnaeus 1758) in a low-Arctic ecosystem in the NW Atlantic. We demonstrate that the gannets foraged almost exclusively on inshore and coastal aggregations of capelin. There was a strong correspondence between the distributions of capelin and foraging gannets, and gannets exhibited persistence in successive foraging trips to the same foraging areas. The diving activity of gannets was highest during the early morning and evening, when capelin are known to be primarily available in the upper water column. Most of the gannets dive depths were less than 5 m. Flight speeds recorded by GPS were 9% higher than those estimated by previous methods and were shown to benefit from tail wind. This study shows how a combination of ship-based surveys and individually tagged birds can help understanding predator–prey intersection in a three-dimensional space in the marine environment.