Bird-borne video-cameras show that seabird movement patterns relate to previously unrevealed proximate environment, not prey.

Abstract

The study of ecological and behavioral processes has been revolutionized in the last two decades with the rapid development of biologging-science. Recently, using image-capturing devices, some pilot studies demonstrated the potential of understanding marine vertebrate movement patterns in relation to their proximate, as opposed to remote sensed environmental contexts. Here, using miniaturized video cameras and GPS tracking recorders simultaneously, we show for the first time that information on the immediate visual surroundings of a foraging seabird, the Cape gannet, is fundamental in understanding the origins of its movement patterns. We found that movement patterns were related to specific stimuli which were mostly other predators such as gannets, dolphins or fishing boats. Contrary to a widely accepted idea, our data suggest that foraging seabirds are not directly looking for prey. Instead, they search for indicators of the presence of prey, the latter being targeted at the very last moment and at a very small scale. We demonstrate that movement patterns of foraging seabirds can be heavily driven by processes unobservable with conventional methodology. Except perhaps for large scale processes, local-enhancement seems to be the only ruling mechanism; this has profounds implications for ecosystem-based management of marine areas.