Through analysis of the inner workings of birds’ cells, scientists have been deciphering increasingly urgent signals from ecosystems around the world.
Like the fabled canaries that miners once thrust into coal mines to check for poisonous gases, birds provide the starkest clues in the animal kingdom about whether humans, too, may be harmed by toxic substances.
And they prophesy what might happen to us as the load of carbon-based, planet-warming gases in the atmosphere and oceans climbs ever higher.
The idea that birds tell us about our own health has gained even more scientific traction in the decades since Silent Spring as biochemical analysis has become more precise. Much of that work stemmed from studies Canadian Wildlife Service toxicologist Glen Fox and others conducted on the Great Lakes, the world’s first and biggest testing ground for contaminants and birds.
Fox’s work began with tales from terns and other fish-eating birds. He found high levels of #polychlorinated_biphenyls (#PCBs) in the lakes and their sediments, and enlarged thyroids that were producing little hormone in the birds. Substances that build up in food webs just like DDT, PCBs were banned in the United States in 1978, with the rest of the world to follow.
By the late 1980s, there was so much research about chemicals in the Great Lakes that zoologist Theo Colborn, then at the World Wildlife Fund, began examining the studies to see if she could discern a big picture.
The results were stunning: The Great Lakes’s top 16 or 17 bird predators were vanishing. The problem stemmed from assaults on the endocrine system, which controls hormones and reproduction. And that, in turn, was linked to man-made substances in the water and prey. So, birds’ ability to reproduce crashed in multiple ways. The concept of the “endocrine disruptor” was born.