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The connection between horseshoe crabs and red knots

Mark Faherty
Red knots and dunlin at Monomoy.

Last week I was lucky enough to accompany some fellow ornithologists on a secret mission to a special place in search of an important bird. Or maybe it was an important place and a special bird. Either way, it was like going back in time, to a Cape Cod that barely exists anymore. There, we saw thousands of horseshoe crabs and shorebirds playing out an ancient ritual that few have seen here in Massachusetts. Armed with the proper permits, we were at Monomoy National Wildlife Refuge in Chatham, the last resort for spring migrating Red Knots in New England. We were looking for one particular Red Knot, the one known, somewhat impersonally, as 242656.

The bird cognoscenti among you are likely are aware of the connection between Red Knots, a lovely and now rare sandpiper, and horseshoe crabs, especially down in Delaware Bay, where their relationship forms the basis of a multi-million dollar shoulder season economy. The federally Threatened subspecies of Red Knot nests somewhere above the Arctic circle in June, then migrates literally to the other end of the planet each fall, to Tierra del Fuego. In May, they fly 6000 miles north to gather on major horseshoe crab spawning beaches from South Carolina to Massachusetts where they feed and fatten on horseshoe crab eggs. Most would not include Massachusetts on that list, because almost no one gets to Monomoy in May.

But last week, we set out to find Red Knot 242656 – ok, that’s a super lame name, so from now on I’m calling the bird “Red Knottington”, as that sounds like someone who would have waterfront property in Chatham. Red Knottington had been captured and fitted with a satellite tracker down in South Carolina back in early May. After a week or so of feeding on horseshoe crab eggs down there, it high-tailed it to Monomoy, where we headed to search it out.

As we pulled up to a network of flats, marshes, and sandbars off North Monomoy, we saw hundreds of paired-up horseshoe crabs in the water, and big flocks of shorebirds on the flats. Before we got to land, a huge chunk of the birds left, but Brad Winn of the conservation organization known as Manomet counted at least 200 Red Knots in the flock as it passed overhead.

While Brad tended the boat, biologist and videographer Ben Clock, and I checked the remaining feeding and roosting flocks for Red Knottington. Though we never laid eyes on Red, we saw astounding numbers of horseshoe crabs and shorebirds. Crabs clambered over each other to spawn, as shorebirds fed on their eggs from previous spawns in the adjacent sandbars – only at Monomoy are there enough spawning crabs laying enough eggs for shorebirds to be able to find them. Red Knots, Ruddy Turnstones, Dunlin, Sanderlings, Black-bellied Plovers, and Short-billed Dowitchers all fed on the tiny green eggs, which were easy to find by scratching in the sand. It was a small-scale version of the famous feeding frenzies further south, happening anonymously in closed and inaccessible areas of a local wildlife refuge.

Mark Faherty
Horseshoe crabs spawning at Monomoy. 

Why are there so many horseshoe crabs and shorebirds at Monomoy? It’s because there, the crabs are protected from all forms of harvest, and the spawning and nursery habitat is protected. It’s an example of what we could have other places if we better managed horseshoe crabs to recover the population.

Sadly, our state Division of Marine Fisheries recently failed to extend even modest additional protections for spawning horseshoe crabs in Massachusetts, where we allow female crabs with eggs to be targeted as they attempt to spawn, partly to provide bait for an overfished whelk fishery. Despite over 1300 public comments in favor of additional protections and ending bait harvest altogether, the protections were rejected by the Marine Fisheries Advisory Commission, a board of fishing industry representatives with the power to veto any proposed state regulations.

Hopefully state officials will rethink this decision, and someday more of us will have the opportunity to see this bit of old Cape Cod play out on local beaches. I felt lucky to witness it last week, but you shouldn’t need a special permit to see the ancient and intimate connection between horseshoe crabs and shorebirds here in Massachusetts.

Mark Faherty writes the Weekly Bird Report.