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During a wildlife survey of wintering locations for migratorybirds, a large number of waterfowl have been found to have died dueto a large dose of a toxic substance. During follow-up research ofthe birds’summering locations and migratory path, no sources of thetoxic substance were found with concentrations sufficient toexplain the body-burden measured in the dead birds.In fact, nosources were found that would have led to a fatal exposure at all(even for young birds) Describe what you consider to be themost-likely cause for the observations above.
