Diet and methyl mercury contamination of nestling red-winged blackbirds.

This article examines the diets and methyl mercury (MeHg) contamination of nestling red-winged blackbirds (Agelaius phoeniceus) at a wetland site in north Texas, USA, to evaluate potential health risks from MeHg exposure. Using stable isotope dietary mixing models and MeHg analyses of prey and nestling blood, the study found that nestling diets were dominated by terrestrial insects, which have low MeHg concentrations, resulting in nestling blood MeHg levels well below thresholds associated with adverse health effects. These findings contrast with prior risk assessments based on literature estimates that assumed diets dominated by emergent aquatic insects with higher MeHg levels, highlighting the importance of site-specific dietary data for accurate risk evaluation. The study underscores the need to integrate ecological diet assessments with toxicological measurements when assessing mercury exposure risks in wetland-associated songbirds.