The highest mercury concentrations ever reported in a South American bird, the Striated Caracara (Phalcoboenus australis)

Mercury is a widely available pollutant associated with negative effects on wildlife, especially top predators. Here, we characterized the mercury concentrations in feathers of Striated Caracara Phalcoboenus australis on Isla de los Estados (Argentina). With feather mercury levels averaging 26.3 mg/kg, this population has the highest mean feather mercury ever reported for a bird population in South America. We propose that the high mercury concentrations are related to the feeding habits of the species: during feather moult, they are strongly associated with a Southern Rockhopper Penguin ( Eudyptes chrysocome ) colony known to be highly exposed to mercury contamination. Our results suggest that this Striated Caracara population should be monitored for acute effects and potential impacts of mercury toxicity.