The Horseshoe Crab Limulus polyphemus During the high tides of the new and full moon in early spring, a female horseshoe crab becomes active. Emerging from the muddy bed where it has spent most of the winter, it begins its journey to shore to take part in the spawning ritual that began millions of years before.
Females dig several nests to lay their eggs.
The males, one-third the size of the females, attach themselves to the rear of the female's carapace and are pulled over the nests to fertilize the eggs. Horseshoe crabs attempt to protect their eggs by covering the nests with sand. Often wind and waves shift the sand and leave many of the eggs exposed. The eggs are eaten by the many migratory shorebirds stopping along the Atlantic coastline. Shorebirds almost double their weight from feeding on horseshoe crab eggs which gives them the energy source that enables them to continue their migration north.