Annual and regional variation in mercury concentrations in wood stork nestlings

Mercury concentrations were measured in blood, down, and feathers from appr oximately 300 wood stork nestlings in one South Carolina, USA, and four Geo rgia, USA. colonies from 1996 to 1999. Coastal nestlings generally had lowe r mercury concentrations than those from inland colonies. Interyear differe nces were also apparent, particularly for coastal colonies, where nestling mercury concentrations were higher in 1998 than in 1997 or 1999. In 1998, a wet winter followed by a dry spring and summer produced ideal freshwater f oraging conditions and mercury concentrations in coastal nestlings were hig her than during the two dry years. There was little interyear variation in mercury concentrations in nestlings from inland colonies. as parent stories from these colonies forage exclusively in freshwater habitats regardless o f rainfall patterns. These results suggest that greater risk of mercury exp osure to nestlings is associated with use of freshwater foraging habitats.