Feathers recently taken from seabirds stuffed and preserved in the 1880s have been found to contain only half as much mercury as feathers recently taken from living birds of the same species.
Evidence
Feathers recently taken from seabirds stuffed and preserved in the 1880s have been found to contain only half as much mercury as feathers recently taken from living birds of the same species.
Mercury that accumulates in a seabird’s feathers as the feathers grow is derived from fish eaten by the bird.
Conclusion
These results indicate that mercury levels in saltwater fish are higher now than they were 100 years ago.
Evaluate
There are two equally likely explanations for the difference in the amount of mercury contained in the seabirds’ feathers. One explanation is the argument’s conclusion that more mercury is being absorbed into feathers than before. Another explanation is that the mercury in the samples of preserved birds somehow dissipated during their period of preservation.