The persistence and degree of mercury contamination of the lower Carson River system (LCRS) have led to placement of a portion of the Carson River Basin (including Lahontan Reservoir) on the US. Environmental Protection Agency (EPA) National Priorities List ("Superfund") for research and cleanup. The potential toxicity of mercury concentrations within the LCRS to piscivorous birds (snowy egrets, black-crowned night-herons, and double-crested cormorants) was examined from 1997-2006.