Total and methyl mercury concentrations in seabird feathers and eggs.

Seabirds are used frequently as indicators of mercury contamination in marine ecosystems, but few studies have examined the forms of mercury found in seabird tissues. Here we compare concentrations of total and organic mercury in feathers (n=5) of six sympatric nesting seabirds and in egg components of Leach's storm-petrels from Machias Seal Island, New Brunswick, Canada, during the 2006 breeding season. Essentially all (82-133%) mercury found in seabird feathers and egg components was methyl mercury, with no interspecific differences in percentage methyl mercury. This pattern is consistent with the hypothesis that feather-molt and egg production eliminate toxic methyl mercury, while inorganic forms from demethylation in the liver remain in internal tissues. Additional studies across more species, and comparisons with percentage methyl mercury in internal tissues, are required to validate this theory.