Atlantic Horseshoe Crabs are a fascinating and ancient species. One of the Earth’s oldest living species—unchanged for 400 million years, predating dinosaurs—their spring breeding behavior is one of nature’s great spectacles. During the breeding season, Horseshoe Crabs migrate to shallow coastal waters like those on the beaches of Jamaica Bay, Queens. They arrive by the hundreds of thousands on the beaches of the Atlantic Coast during the new and full moons in May and June. 

A female horseshoe crab can lay up to 120,000 eggs during this period, in batches of a few thousand at a time. These eggs are a critical food supply for migrating shorebirds like the Red Knot. Although horseshoe crab eggs may seem abundant, declines in horseshoe crab populations due to over-harvesting are believed to be connected to declines in the migrating shorebird populations. 

Shorebirds travel awe-inspiring distances as part of their migrations each year. For instance, the federally-threatened Rufa Red Knot The Rufa Red Knot is a federally-threatened bird that flies from the Arctic to South America and back every year, covering a distance of about 18,000 miles annually. Along this journey, it stops at select breeding grounds like the shallow waters of Jamaica Bay, where hundreds of thousands of Horseshoe Crabs come ashore to spawn. The eggs of these ancient creatures provide an abundant and nutritious food source for the hungry Red Knots, who need to replenish their energy reserves before completing their migration. Without these eggs, many Red Knots would not survive.

Red Knots rely on a variety of marine invertebrates for food, but they rely on horseshoe crab eggs because they are more nutrient-dense than other sources. However, horseshoe crab populations have declined due to overharvesting for bait and biomedical purposes. This has reduced the amount of eggs available for Red Knots at Jamaica Bay and other stopovers like Delaware Bay, imperiling this magnificent species.  

As a result of declining Horseshoe Crab populations, Red Knots are now listed as threatened under the federal Endangered Species Act and have been placed on New Jersey’s endangered species list. Since 2009, NYC Audubon’s corps of community scientists has monitored several beaches on which horseshoe crabs spawn in Jamaica Bay, gathering data on horseshoe crab numbers. Our monitoring is part of a statewide project led by Cornell Cooperative Extension of Suffolk County in partnership with the New York State Department of Environmental Conservation, to survey horseshoe crabs spawning populations, in order to inform conservation and management plans.

To help horseshoe crabs, NYC Audubon also pushes for: