Mercury exposure in terrestrial birds far downstream of an historical point source.

Mercury (Hg) is a persistent environmental contaminant found in many freshwater and marine ecosystems. Historical Hg contamination in rivers can impact the surrounding terrestrial ecosystem, but there is little known about how far downstream this contamination persists. In 2009, we sampled terrestrial forest songbirds at five floodplain sites up to 137 km downstream of an historical source of Hg along the South and South Fork Shenandoah Rivers (Virginia, USA).

Stability of mercury concentrations in frozen avian blood samples.

It is unclear whether mercury concentration in wildlife tissues changes appreciably after lengthy frozen storage. To test whether such freezer-archived samples are stable, small (~10-50 μL) avian blood samples stored in capped glass capillary tubes were analyzed for total mercury concentration, and then reanalyzed after being frozen for up to 3 years. Mercury concentrations increased 6% on average over the 3 year period, but time spent frozen explained only 11% of the variation between measurements.

Feather growth influences blood mercury level of young songbirds.

Dynamics of mercury in feathers and blood of free-living songbirds is poorly understood. Nestling eastern bluebirds (Sialia sialis) living along the mercury-contaminated South River (Virginia, USA) had blood mercury levels an order of magnitude lower than their parents (nestling: 0.09 +/- 0.

The movement of aquatic mercury through terrestrial food webs.

Mercury has contaminated rivers worldwide, with health consequences for aquatic organisms and humans who consume them. Researchers have focused on aquatic birds as sentinels for mercury. However, trophic transfer between adjacent ecosystems could lead to the export of aquatic mercury to terrestrial habitats.