Foraging seabirds respond to an intermittent meteorological event in the Ria de Vigo, Spain.

Abstract

**Abstract:** Temporal variations in the numbers of foraging seabirds usually coincide with concurrent variations in physical processes influencing prey availability. Responses to periodic tidal currents are commonly reported, with certain tidal states being favoured. By contrast, responses to intermittent meteorological events have rarely been reported, even though wind-driven exchanges of water masses or intrusion of estuarine plumes could have similar consequences. This study compares responses of foraging seabirds to physical processes in the Ria de Vigo, north-western Spain. The numbers of foraging European shags Phalacrocorax aristotellis and yellow-legged gulls Larus michahellis showed no response to variations in current direction/speed. By contrast, the numbers of both species increased during the intrusion of the Western Iberian Buoyant Plume following high freshwater discharge and southerly winds. The differences in responses to periodic tidal currents and intermittent meteorological events presumably relate to their relative control of conditions in the ria; whilst currents cannot be considered particularly weak, intermittent weather events have a stronger control on conditions. These findings show that responses to periodic tidal currents could be absent or subdued when intermittent meteorological events have a greater control on conditions, even though periodic tidal currents are conspicuous physical processes in coastal environments. **Authors:** James Waggitt¹, Shaun Fraser², Ricardo Torres³ ¹Bangor University, ²University of Highlands and Islands, ³Plymouth Marine Laboratory