Foraging areas of Orlog’s gulls in an estuarine ecosystem of Argentina: are they underprotected?

Abstract

Worldwide, seabird populations 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 (FAs) is essential for their conservation. In this study, the focus was on Olrog’s gull (Larus atlanticus), a near-threatened species endemic to the Atlantic coast of Argentina, Uruguay, and southern Brazil. The objectives were to assess the distribution of FAs and home ranges of Olrog’s gull and to evaluate the overlap between FAs and protected areas (PAs) in the Bahía Blanca Estuary (BBE), Argentina. Global positioning system (GPS) tracking and dynamic Brownian bridge movement models (dBBMM) were used to analyze Olrog’s gull behavior during their breeding season. The results revealed well-defined FAs, with 72% of them located outside PAs, raising concerns about potential threats to the species. Sex-related differences were observed, with females covering longer distances during foraging flights. In addition, several FAs were located near industrial sites, posing health risks due to pollution. This study contributes novel insights into Olrog’s gull foraging ecology, particularly in the most critical breeding area for the species. A dynamic web application was developed to provide rapid access to comprehensive information applicable to conservation actions. These findings underscore the need for enhanced protection of critical FAs, particularly those lying outside currently PAs.