The Unraveling of the Red Knot

The red knot is one of the region’s most extraordinary birds, facing one of conservation's biggest threats, but sadly flies under the radar of too many people. Too few of us have heard of the knot, and fewer still know its story, which has a deep and ancient connection to another important animal, the horseshoe crab.

And May is the time to get to know this bird, the crab, and this extraordinary story.

A nine-inch-long sandpiper with a terra cotta belly, the red knot makes one of migration’s longest runs, flying 9,300 miles each spring from Tierra del Fuego at the bottom tip of South America to nest above the Arctic Circle in the spring. 

Somewhere around Mother’s Day, the exhausted birds-- their gas tanks nearing empty-- land on beaches along the Delaware Bay, looking for a critical food source to fuel them on the rest of their journey north. The famished birds need food rich in fats, and that’s where the horseshoe crabs come in.

In one of nature’s best-timed events, horseshoe crabs, those prehistoric living fossils that have lumbered across ocean bottoms for 450 million years, haul themselves onto beaches, large females usually with an entourage of smaller male hangers-on, to mate and lay eggs in the surf, each female laying 80,000 eggs, each egg a small green BB. They especially emerge in the full and new moons of high tides at night, a spectacle worth seeing in itself, as Delaware Bay is the single largest concentration of mating horseshoe crabs on the planet. (Bet you didn't know that.)

So just when red knots and other migrating shorebirds need fat-rich food, Delaware Bay beaches are loaded with fatty crab eggs roiling in the surf. The shorebirds enjoy a raucous debauchery of nonstop feeding, filling up on the eggs that give them the energy they need to finish the trip.

Many other shorebirds join them in this feast, including other sandpiper species like dunlins and sanderlings, plovers, ruddy turnstones, willets, and more, not to mention laughing, herring, and black-backed gulls, plus terns. 

It is a sight to behold. Arrive at low tide, and the beaches are crammed with shorebirds, gulls, and terns cheek-to-jowl in a frenzy of feeding, the cacophony of gulls impossibly loud; arrive at nighttime high tide, and the beach is chock-a-block with horseshoe crabs. It is a naturalist’s nirvana. On my visit in 2021, I easily spotted a huge turkey vulture inexplicably sitting amidst the gulls, quietly munching on dead horseshoe crabs while the gulls noisily fought over eggs. I've even seen bald eagles sitting on the beach at low tide at this time of year too, their size standing out among the Lilliputian shorebirds.

Call it sex and gluttony on the Delaware Bay: the horseshoe crabs engaged in lusty orgy while the shorebirds engorge themselves on the fruits of the crabs’ labors. 

But this extraordinary confluence of natural history events is depressingly endangered. While horseshoe crabs have been used for fertilizer since the Lenape days, in recent decades the overharvesting of the beasts for fertilizer, bait, and even medicine (the crab’s blue copper-based blood is useful to researchers) has greatly depleted their numbers. With fewer crabs emerging in the surf, knot numbers have plummeted, and bird experts are terrified we will lose the race of knots that engages in this long-distance feat. Over the last 20 years or more, there have been fierce battles raging over the allowable number of crabs to sustainably harvest, arguments leaving no one happy, neither biologists nor fishermen. And because three states border on the bay, the knot’s situation becomes even more entangled.

For the last 25 years or more, Dr. Lawrence Niles has been leading national efforts to call attention to the plight of both red knots and horseshoe crabs, and has been featured in many TV and radio news shows over the years. Niles has had a front row seat on the red knot story, spending two decades as chief of New Jersey’s Endangered and Nongame Species Program, where he works on other species like piping plovers, and in 2006 started his own company to pursue independent research and habitat restoration in the Delaware Bay and elsewhere. He is also a founding member of the Horseshoe Crab Recovery Coalition and on the board of the National Shorebird Council and Western Hemisphere Shorebird Reserve Network.  

“Over the last year,” he said, “we have built the Horseshoe Crab Recovery Coalition to fight the wasteful killing of horseshoe crabs for bait and at the hand of multinational corporations for their blood despite an effective synthetic alternative.” He’s hard at work researching the ecological significance of horseshoe crabs, showing that their importance is far greater than eggs for shorebirds. At their natural levels, he concluded, ”they are a foundational resource for coastal ecosystems.” 

Where to see them

While numerous beaches on both sides of the Delaware Bay offer wonderful opportunities to check in on both crabs and birds, several beaches just north of Cape May offer you good views along with access to experts monitoring the situation. My book, Wild Philly, describes the best beaches in Field Trip 26 starting on page 340.

At least five beaches on the Jersey side are available to you: Reeds Beach, Cooks Beach, Kimbles Beach, Pierce’s Point, and Norbury’s Landing. All are easily accessible off N. Delsea Drive, Route 47, the road so many Philadelphians take to Cape May. 

Start at Reeds Beach, the northernmost of the five. Driving south on Rt, 47, turn right onto Reeds Beach Road and take this to its end, turning right on Beach Drive and taking this to the end. Park on the road, and you’ll find a stone jetty jutting into the bay. Walk the jetty to its end, and you’ll see the beach-- with signs interpreting the migration, and ropes asking you not to walk any further. 

Then follow the directions outlined in the book, and make sure you talk to volunteers and other birders there to hear the full story.

After visiting these sites, consider visiting one of the three New Jersey Audubon centers in operation in the area, any one of which is worth visiting: the Cape May Bird Observatory on Rt. 47, the Nature Center of Cape May on the ocean side of Cape May, and another observatory in Cape May Point. Ask them how you can help untangle the red knots from their plight.