Each spring, hundreds of thousands of shorebirds migrating north from Central and South America inundate the Delaware Bay shore, where many make their final rest stop before continuing to Arctic breeding grounds. They rest here because of the variety of coastal habitats and the abundance of food, mainly horseshoe crab eggs. Their arrival is amazingly timed with the spawning season of the Atlantic horseshoe crab (Limulus polyphemus). Starved and exhausted after using all of their fat reserves in migratory flight, many of these birds double their weight by feasting on horseshoe crab eggs and small invertebrates during their two week rest. They feed at sandy beaches and tidal mudflats during the day and roost in the security of the marshes at night. Habitat destruction, human disturbance, and a recent decline of horseshoe crab populations threaten the survival of these migratory birds.