Foraging areas of Orlog's gull in an estuarine ecosystem of Argentina: are they underprotected?

Abstract

Seabird populations worldwide are facing significant declines due to various threats, making them valuable bioindicators of marine ecosystem changes. Understanding their foraging behavior and identifying crucial foraging areas is essential for their conservation. In this study, we focused on Olrog’s Gull (Larus atlanticus), a near-threatened species endemic to the Atlantic coast of Argentina, Uruguay, and southern Brazil. Our objectives were to assess the distribution of foraging areas (FAs) and home ranges, describe temporal flight patterns, and evaluate FA overlap with protected areas in the Bahía Blanca Estuary (BBE), Argentina. We used GPS tracking with dynamic Brownian bridge movement models (dBBMM) to analyze Olrog’s Gull behavior during their breeding season. Our results revealed well-defined FAs, with 72% of them being located outside protected areas, raising concerns about potential threats to the species. We observed sex-related differences, with females covering longer distances during foraging flights. Additionally, several FAs were situated near industrial sites, posing health risks due to potential pollution. This study contributes novel insights into Olrog’s Gull foraging ecology, particularly in the most critical breeding area for the species. We developed a dynamic web application for easy access to conservation-relevant information. Our findings emphasize the need for enhanced protection of key FAs, especially those outside existing protected areas, to safeguard the species and its ecosystem. These results underscore the importance of informed policy decisions to preserve Olrog’s Gull populations and their habitats in the face of growing human-related threats.