Every year, tiny birds known as red knots fly 19,000 miles – from the tip of South America to the Arctic and back. They’re able to do it thanks to their food source – tiny horseshoe crabs. This hour, we’ll learn how climate change is having a domino effect on these birds – and what their addition to the endangered species list could mean for us – with Deborah Cramer, author of The Narrow Edge: A Tiny Bird, an Ancient Crab, and an Epic Journey (Yale University Press).