ナショナルジオグラフィックのインスタグラム(natgeo) - 8月13日 09時00分

Photo by @peteressick | A tree swallow parent brings food to chicks inside the box on the bank of the Rouge River, Detroit, Michigan. In the background is a steel mill on Zug Island. Tree swallows feed on insects in the river, so they are an excellent indicator species concerning the amount of chemical pollution in the water. A scientist from the U.S. Geological Survey is conducting a study now - before dredging of contaminated sediments on the bottom of the river - to determine the level of chemicals in the tree swallows' blood. Hopefully, after restoration, the levels will decline. #greatlakes #restoration #sediments

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