Mark A. Ricca Cory T. Overton John Y. Takekawa Angela Merritt Joshua T. Ackerman Michael L. Casazza 2015 California Clapper Rails (<i>Rallus longirostris obsoletus</i>) are an endangered waterbird that forage in tidal-marsh habitats that pose risks from mercury exposure. We analyzed total mercury (Hg) in six macro-invertebrate and one fish species representing Clapper Rail diets from four tidal-marshes in San Francisco Bay, California. Mercury concentrations among individual taxa ranged from lowest at Colma Creek (mean range: 0.09–0.2 μg/g dw) to highest at Cogswell (0.2–0.7), Laumeister (0.2–0.9) and Arrowhead Marshes (0.3–1.9). These spatial patterns for Hg matched patterns reported previously in Clapper Rail blood from the same four marshes. Over 25% of eastern mudsnails (<i>Ilyanassa obsolete</i>) and staghorn sculpin (<i>Leptocottus armatus</i>) exceeded dietary Hg concentrations (ww) often associated with avian reproductive impairment. Our results indicate that Hg concentrations vary considerably among tidal-marshes and diet taxa, and Hg concentrations of prey may provide an appropriate proxy for relative exposure risk for Clapper Rails. application/pdf 10.1016/j.marpolbul.2014.07.009 en Pergamon Dietary mercury exposure to endangered California Clapper Rails in San Francisco Bay article