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Songbirds as Sentinels of Mercury in Terrestrial Foodwebs of Eastern North America
Citation:
Jackson, A. K., D. C. Evers, E. M. Adams, D. A. Cristol, C. Eagles-Smith, S. T. Edmonds, C. E. Gray, B. Hoskins, O. P. Lane, A. Sauer, AND T. Tear. Songbirds as Sentinels of Mercury in Terrestrial Foodwebs of Eastern North America. Ecotoxicology. Springer, New York, NY, 24(2):453-467, (2015).
Impact/Purpose:
The results of this study present the most comprehensive assessment of blood mercury concentrations in eastern songbirds to date, and thereby provide a valuable framework for designing and assessing risk assessment schemes using sentinel songbird species in the time after implementation of the USEPA Mercury and Air Toxics Standards rule.
Description:
Mercury is a globally distributed environmental contaminant with a variety of deleterious effects in fish, wildlife, and humans. Breeding songbirds may be useful sentinels for mercury because they are relatively easy to sample, have well-defined and small territories, and integrate pollutants over time and space. Very little information exists, however, to aid the interpretation of songbird mercury concentrations across the habitats, foraging guilds, species, and age classes represented by this diverse taxon. We analyzed blood total mercury concentrations from 8446 individuals of 102 species of songbirds, sampled on their breeding territories across 161 sites in four ecoregions of eastern North America. Mixed effects modeling indicated that habitat, foraging guild, and age were important predictors of blood mercury concentrations across species and sites. Blood mercury concentrations in adult invertebrate-eating songbirds were consistently higher in wetland habitats (freshwater or estuarine) than upland forests. Generally, adults exhibited higher blood mercury concentrations than juveniles within each habitat type. Our records span an important time period – the decade leading up to implementation of the USEPA Mercury and Air Toxics Standards, which will reduce mercury emissions from coal-fired powerplants by 90%. We used model results to examine species-specific differences in blood mercury concentrations during this time period, identifying potential mercury sentinels in each ecoregion and habitat type affected by atmospheric mercury emissions.
