Integrating telemetry with metrics of marine biodiversity reveals linkages between movements, feeding, and reproductive success in a seabird

Movement is a fundamental aspect of ecology, facilitating species interactions, transport of energy, and ultimately ecosystem function. Central place foragers such as seabirds can be highly mobile and thus flexible to variable foraging conditions, but also constrained by the needs to return, such as to feed young. Determining how flexibility in movements allows animals to withstand variations in foraging conditions is important for predicting resilience to climate change and other stressors. Such linkages would also quantify how animal movement relates to biodiversity. Our study explores the role of foraging movement in prey capture and reproductive success in a central place foraging seabird, the common tern (Sterna hirundo), in a breeding colony in the Northwestern Atlantic. Over four years (2021-2024), we collected movement (GPS telemetry), prey provisioning to chicks, and reproductive success data from common terns nesting on a colony in the Gulf of Maine (GOM). In years of high preferred prey (herrings, hakes, and sand lance) abundance and high chick survival, common terns largely foraged close to the colony at productive nearby river mouths. Conversely, in years of low preferred prey abundance and low chick survival on the colony, common terns increased foraging trip durations by up to 87% and expanded foraging ranges by up to 52%. Range expansions were driven by increased use of waters in the Stellwagen Bank region, which is encompassed within the GOM’s only national marine sanctuary and in which sand lance are abundant. Our results suggest that common tern foraging movements are flexible in response to forage fish availability, but that increased foraging movement effort in low-productivity years may be insufficient to maintain survival of chicks. This case study demonstrates how movement data can be indicative of not only the animal’s success, but also of local ecosystem productivity and biodiversity. Scaling such observations across colonies would facilitate monitoring of biodiversity and forage fish distribution and abundance, impacting conservation and fisheries management.