Horseshoe Crabs and Red Knots in New Jersey

Labeled living fossils, horseshoe crabs date back in the fossil record more than 350 million years.  Not true crabs at all, these marine animals are actually more closely related to spiders and scorpions than Crustaceans (the group that includes crabs, lobsters and shrimp).

Pair of horseshoe crabs returning to the water – Higbee Beach, NJ

Spring moons summon horseshoe crabs from the ocean floor to beaches and estuaries.  Full moons in May and June create the highest tides and that’s when the largest numbers of horseshoe crabs spawn.   We scheduled this year’s trip to Cape May, New Jersey for the Audubon Society of Greater Denver to correspond to May’s full moon.  As an added bonus, we had a Supermoon on May 5, 2012 and horseshoe crabs were out of the water in huge numbers along the bay side of the Jersey shore.

Horseshoe crabs spawning during Supermoon at High’s Beach, NJ (May 5, 2012).


May also corresponds to peak migration for shorebirds and neotropical songbirds along the northeast coast of the US.  Every year, an estimated 425,000 to 1,000,000 migratory shorebirds converge on Delaware Bay to feed and rebuild energy reserves before continuing further north to their breeding grounds.  Red knots were of particular interest to us since they exhibit one of the longest animal migrations on earth, from the tip of South America to the Arctic.

Shorebirds at Stone Harbor Beach near Cape May, NJ.

We started our trip with the Supermoon and spawning on the first day at High’s Beach, NJ.  On our last full day of birding, we spotted a single red knot amongst several hundred sanderlings at Stone Harbor Beach.  What a way to come full circle!

There is one red knot in this group of sanderlings. It’s towards the bottom of the photo and in the middle. It stands taller than the sanderlings and has a buffy-chestnut breast. Can you see it?