Understanding Mercury Concentration Levels in Feathers of Wood Ducks

Abstract

Contaminants in game species are an established concern because of the accumulation of chemical toxins that might be harmful to both waterfowl and humans. Mercury (Hg) occurs in water and sediments, and levels of contamination among individuals varies based on degree of exposure. We examined mercury levels in feather types, comparing between axillary and flank feathers to evaluate if there was variability in Hg bioaccumulation between those types of feathers. We also examined mercury levels in feathers of male and female wood ducks (Aix sponsa) to evaluate if one sex is more susceptible to contamination than the other. Lastly, we looked at age class, to determine if adult or young wood ducks were more susceptible to Hg bioaccumulation. The Carson River in Fallon, Nevada, has been shown previously to have high concentrations of methyl mercury (MeHg) because of the state’s mining history during the Comstock Era of the 1860s. We hypothesized that females would have higher concentrations of mercury in feathers than males because they were nesting and raising clutches along the Carson River. Conversely, male wood ducks have more variation in movements away from the Carson River because males were not restricted to nesting and brooding. Our data demonstrated that variation does occur in Hg bioaccumulation between axillary feathers that molt once in the season compared with flank feathers that are molted twice in the season. Our data also revealed that female wood ducks tended to have higher concentrations of mercury in feathers than their male counterparts. Our findings also showed young wood ducks tend to have higher Hg concentration levels when compared with adults. Therefore, assessments of populations within Fallon, NV, will require continuous examination and monitoring of contamination levels to ensure healthy, viable wood duck populations that will persist into the future.