Try Tom's Cove on Chincoteague Island, or the Great Bay of New Hampshire, or even the beaches of Key West. But to appreciate fully the crab's primeval nature, and critical relevance, visit Delaware Bay in late spring. During the peak high tides of the new and full moons, horseshoe crabs storm the beaches there by the hundreds of thousands to spawn. Perhaps 80 percent or more of the entire North American horseshoe crab population migrates to the inner curve of New Jersey's Cape May peninsula, and Delaware's shoreline on the opposite side of the bay. Beaches turn from light beige to a dark, crawling brown in one of nature's most impressive, and bizarre, spectacles.
Strange shapes cloud the mottled waves as the assault on the shoreline begins.
Many crabs hit the sand already hitched, literally, as males use specialized clasping pincers to attach themselves to their mates' abdomens, and ride the waves to shore in tow. You may observe a female dragging three or four males slowly up the beach. Inevitably, crabs on the more crowded breeding beaches dig up previously laid nests, and kick the older eggs to the surface. These small birds stop only briefly at Delaware Bay, but it's often their only lay-over on migrations from wintering grounds in South America some ten thousand miles north to the Canadian Arctic. A million birds or more arrive on the shores of Delaware Bay each spring, making it one of the largest and densest concentrations of migratory birds on the planet.