Loons in Wisconsin, and walleye and northern pike in Minnesota are among the species showing increasing levels of mercury contamination. At this point, scientists don't know why the levels are rising.
Scientists find more birds with mercury contamination in Great Lakes area
A new report is one of few to measure mercury contamination in songbirds, which rely on insects for food. Until recently, scientists believed mercury contamination was mostly a problem for aquatic birds that eat fish. The report says "the scope and intensity of the impact of mercury on fish and wildlife in the Great Lakes region is much greater than previously recognized."