In the spring of 1958, when the winter snow melted and the warm sun returned, the birds did not. Birdwatchers, ordinary people, everyone wondered where the birds had gone. Rachel Carson, a journalist and early environmentalist, figured it out — they’d been poisoned by DDT, a pesticide that towns all over the country had been spraying. Carson wrote a book about it, Silent Spring. It succeeded in stopping DDT, and it launched the modern environmental movement. But now, more than 60 years later, birds are dying off en masse again. Our question is simple: What are the birds trying to tell us this time, and why can’t we hear their message any more?