Sarah Wraight, myself, and Betsy Robson presented "Re-imagining the Future of Onondaga Lake"
to F.O.C.U.S. Greater Syracuse last Friday morning. There were a number of good questions asked afterward, including one asking about the impact of the mercury pollution of Onondaga Lake on the eagles.
Mercury in Onondaga Lake is primarily found in the sediments; it enters the food chain through bacteria at the bottom of the lake, which are then eaten by macroinvertebrates (underwater bugs), then fish, and then eagles. Because fish eat many macroinvertebrates, eagles eat many fish, and mercury is not easily eliminated from their systems, it "bioaccumulates". The US Fish and Wildlife Service studied songbirds and shorebirds around Onondaga Lake. These birds' diets rely on the macroinvertebrates when the bugs reach the flying stage of their life.
"Data collected through this study will help evaluate whether or not mercury levels on Onondaga Lake are a concern to other bird species, including bald eagles that winter in large numbers on the lake," the USFWS website states. "The study showed blood levels of mercury that were as high as 2 parts per million in those birds, while the threshold of concern for sensitive species is closer to 0.6 parts per million. Further studies are now being conducted."
In other words: the birds have reason to be concerned about what they're eating.
