Artwork and story by Nancy Edwards

Each spring, between the Delaware Bay and the Atlantic Ocean the sandy coastline of New Jersey hosts two of the most amazing annual events in nature — the migration of the Red Knot and the spawning of the American Horseshoe crab.

Red Knots (Calidris canutus rufafly) fly more than 18,000 miles in their annual migration between wintering areas in South America to breeding grounds in the Canadian arctic. Red Knots are one of the longest-distance migratory birds seen in North America.

As the Red Knots drop by, on the last stop of their migratory journey north to their breeding grounds, they are just in time for a feast. Hordes of Atlantic horseshoe crabs (Limulus polyphemus) are scrambling up onto the beaches to spawn, laying millions of eggs. For the hungry birds, it is a food fest. These energy packed eggs are unlike any other food source and allow the birds to essentially double their body weight in a short three-to-four-week period. This weight gain will enable them to make the remaining 4,000 miles of their journey northward.

New Jersey shores host the largest concentration of spawning Atlantic horseshoe crabs in the world. As part of the arachnid family, more closely related to spiders and scorpions rather than to crabs, horseshoe crabs have roamed the ocean floors for more than 450 million years. Their body design protects every vital organ beneath an armor-like shell with a horseshoe shaped front. Like armor, the shell flexes in two places, allowing the animal to swim or turn itself over if toppled upside down.

Peak spawning season for the Atlantic horseshoe crab in New Jersey is from May to June. Around the full and new moon, the crabs come ashore during high tide at sunset and into the night to spawn. After laying their eggs, they return to the sea for an entire year until the next spawning season. During rough weather, up to 10% of the crabs are flipped over onto their backs by waves and become stranded. Horseshoe crabs can use their tails to flip themselves back over, but they are not always successful. Those that are unsuccessful die and become food for other birds.

Horseshoe crabs may live up to twenty-five years and may molt seventeen times discarding their smaller shell as they grow to reach maturity. In the last two decades, for numerous reasons there has been a significant decline in the horseshoe crab population which has also impacted those migrating shorebirds who depend on crab eggs for fuel to complete their migrations to breeding grounds. The Red Knot has been placed on New Jersey’s Endangered Species list.
Red Knot migration and fly thru dining can be seen May to June at the outgoing tide at beaches in New Jersey where horseshoe crabs are spawning.

The best time to see horseshoe crab migration in New Jersey:
• May through June
• Calm nights, low wind, and surf
• Nighttime high tides around the new and full moons
Horseshoe crabs are a valuable part of the ecosystem. Helping a horseshoe crab helps migratory birds. Horseshoe crabs do not bite or sting.

Things you can do to help horseshoe crabs:

• Just flip it over: If you see a horseshoe crab upside down on the beach, just flip it over by using the edge of its shell and release it back into the water. Do not use its tail, as it is very delicate and can be damaged. And although its tail looks scary, it is not a weapon.

• Report a Horseshoe Crab Spawning Beach: Report spawning activity by accessing the form entitled “Identification of Horseshoe Crab Spawning Habitat in the Inlets and Bays of New Jersey,” or by calling the toll free phone number 1-866-NJ-CATCH (1-866-652-2824).

• Join the Horseshoe Crab Count:

• Check out The Wetlands Institute to participate in various activities:
Adopt a Horseshoe Crab/Attend a Shorebird and Horseshoe Crab Celebration Day / Donate. Your donation will be used to fund horseshoe crab conservation activities at The Wetlands Institute, such as spawning surveys, reTURN the Favor program activities, aquaculture maintenance, and outreach and conservation initiatives and materials.

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