Foraging behaviour and diet of American Oystercatchers in a Patagonian intertidal area affected by nutrient loading

GARCÍA GO, JP ISACCH, A GÓMEZ LAICH, M ALBANO, M FAVERO, DA CARDONI, T LUPPI & O IRIBARNE

Emu - Austral Ornithology

CSIRO PUBLISHING

Año: 2010 vol. 110 p. 146 - 154

0158-4197

Eutrophication increases the biomass of opportunistic green macroalgae that cover intertidal zones. Macroalgal blooms may affect the intertidal invertebrate community and predation of invertebrates by shorebirds. In San Antonio Bay (40º44´S, 54º68´W) eutrophication by the discharge of wastewater from a coastal town produces periodic macroalgal blooming. Our aim was to assess if macroalgal blooms affect the foraging behaviour and diet of the American Oystercatcher (Haematopus palliatus). A macroalgae transplant experiment was made in order to evaluate how epifaunal species respond to macroalgal canopy. Oystercatchers´ prey availability, foraging behaviour and diet were analyzed in two paired channels with different nutrient loading. Oystercatchers generally consumed the most profitable prey and avoided prey with a value of profitability lower than the average energy intake rate mean. During the period with macroalgal blooms, oystercatchers avoided two prey species with high profitability values shifting their foraging strategy and feeding on a suboptimal prey but with a high encounter rate. Our results suggest that nutrient loadings and the macroalgal bloom that they generate have effects on the diet and foraging behaviour of oystercatchers, which results in an increase of the average energy intake rate of oystercatchers foraging along the channel with macroalgae.