Spatial and Temporal Variation of Beached Birds in Northern Argentine Patagonia

Beached birds on marine coastal beaches, along with other megafauna, are a valuable source of biological information, offering insights into species occurrence and factors that negatively affect their populations. The main objective of this study was to evaluate the spatial and temporal variation, and species composition, of coastal and marine birds found on sandy beaches in the Bahía de San Antonio Protected Natural Area (Río Negro Province, Argentina), and to relate resulting species abundance and richness to oceanographic and environmental variables. A biweekly survey was carried out over two years (2020-2022), during which 672 beached birds were recorded. The overall encounter rate of beached birds was 1.35 birds/km. Most birds were identified to the species level, totaling 27 species belonging to 11 orders. The three most frequently encountered species were Magellanic Penguin Spheniscus magellanicus (49.38%), Kelp Gull Larus dominicanus (43.75%), and Neotropic Cormorant Nannopterum brasilianum (22.5%). The height of high tide and wind direction significantly affected beached bird abundance at various spatial and temporal scales. We conclude that the assemblage of beached birds is heterogeneous, mainly consisting of species that inhabit the Río Negro Province coast, rather than those from farther offshore. Future studies in the area should include drift experiments and cover a larger geographic scale.