Vermont Center for Ecostudies Discovers Toxic Mercury in Caribbean Songbirds

Dominican-Republic-Fo_Balt-1The Vermont Center for Ecostudies (VCE) has documented the potent neurotoxin mercury in Caribbean songbirds, suggesting that the pollutant is moving in the atmosphere from industry smokestacks to tropical forests. Team leader Chris Rimmer belies that the danger may originate in industrialized nations far from the Caribbean. Here are excerpts with a link to the full article below.

A VCE-led research team detected elevated levels of mercury in the bloodstreams of nine forest bird species on the island of Hispaniola, the first such evidence of mercury in Caribbean land birds. Although the study did not identify sources of the mercury, VCE’s findings support growing evidence that the toxin is more pervasive than scientists once believed. “We’ve now established mercury as a potential danger to tropical landbirds,” said Chris Rimmer, VCE’s executive director and leader of the research team, which published its finding in the journal Ecotoxicology. “And we believe that the danger, at least in part, originates in industrialized nations far from the Caribbean.”

That mercury is turning up in thrushes, tanagers, warblers and other forest birds is unusual. [. . .] After documenting the mercury threat in high-elevation forests of the northeastern United States, VCE and its team investigated forests of the Dominican Republic. From 2005 to 2011, the biologists measured mercury levels in 365 individual birds of nine species occupying a range of sites and habitats. Every individual of all nine species showed elevated blood concentrations of mercury.

Birds in remote, mountainous cloud forests showed much higher mercury levels, on the order of two- to 20-times higher, than birds in lower-elevation rain forests. [. . .] Two songbird species featured in the study, Bicknell’s Thrush and Ovenbird, winter on Hispaniola and migrate to North America in spring. Blood mercury concentrations in each were higher than levels researchers typically find in either species when they are on breeding grounds in North America. Local sources of mercury, from cement factories or smelters, may account for some of the exposure in the Dominican birds. But scientists also implicate a global reservoir of mercury, generated at industrial sources and transported in the atmosphere to distant ecosystems. [. . .]

The levels of elevated mercury found in the Caribbean are probably not killing birds outright, said Rimmer, but the toxin is known to impair reproductive performance, growth and development, motor skills, and survivorship in some birds and other wildlife. Mercury can also concentrate progressively over time in the tissues of an organism, presenting risks even if environmental levels of the toxin are low — a process known as bioaccumulation. Coal-burning power plants are the largest human-caused source of mercury emissions in the United States. The U.S. Environmental Protection Agency estimates that one quarter of U.S. emissions from coal-burning deposit mercury within the contiguous U.S., while the remainder enters the global cycle.

VCE and other mercury experts say the findings support the need for tighter controls on mercury emissions and more research, including investigations into modes of mercury transport in the atmosphere.

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