"Each year, red knots, sandpipers weighing no more than a coffee cup, fly a near-miraculous 19,000 miles from the tip of South America to their nesting grounds in the Arctic and back. Along the way, they double their weight by gorging on millions of tiny horseshoe crab eggs. Horseshoe crabs, ancient animals that come ashore but once a year, are vital to humans, too: their blue blood safeguards our health. Now, the rufa red knot, newly listed as threatened...