Horseshoe Crabs Essential for Bird Species’ Survival

If there’s a 21st century “canary in a coal mine” — an early warning signal of climate change — it could be embodied in tiny red knots, sandpipers the size of tea cups who fly more than 9,000 miles each way from the tip of South America to the Arctic and back each year. Fueled solely by the eggs of prehistoric horseshoe crabs. Red knots have just been classified as “threatened” under the Endangered Species Act. And few people know more about why that matters than Deborah Cramer, author of “A Tiny Bird, an Ancient Crab and an Epic Journey”. NJTV News Anchor Mary Alice Williams recently asked her what the plight of the red knot foretells.

Williams: What does the flight of the red knot foretell?

Cramer: The red knot has to migrate these huge distances as you just described and it’s really important for them to have enough food at every stop. Delaware Bay, the Avian Serengeti of short bird migration along the Eastern Seaboard is probably their most important stopover. It’s where they eat their very last meal before they fly up to the Arctic to lay their eggs.

Williams: And they really have to double their weight during that one feeding, right?

Cramer: Yes, they double their weight. Sometimes in as few as 10 days. Imagine if you had to do that.

Williams: You discovered the resiliency, the fortitude of the birds firsthand. It was able to fly through an arctic hurricane that grounded you and your team. Tell us that story. It’s really remarkable.

Cramer: Well, we were flying up to the Arctic to a small island just south of the Arctic Circle — South Hampton Island — and we flew into a caillouet in Basset Island first where we were going to pick up the bush pilots who were going to take us. Because they couldn’t tell the difference between the snow on the ground and the clouds in the sky. The storm was so fierce we were grounded for at least four days.

Williams: But these tiny birds made it through, right?

Cramer: Finally when the weather cleared we arrived on the island and when we got off the plane there were about a dozen red knots there and one of them had a flag on it and I immediately squandered my five minutes of satellite phone time a week to call and find out where that bird had been seen last and it was still in Delaware Bay long after I had left to come up to the Arctic. So while we were sitting in a caillouet, grounded, watching movies, this bird was flying through a hurricane.

Williams: It fares so strong. Why is it threatened?

Cramer: They’re threatened because in order to fly through a hurricane, or detour 600 miles around one which they’ve also been seen doing, they have to have amazing amounts of energy in order to be able to do that. And the way they get their energy is by eating those horseshoe crab eggs in Delaware Bay. In order to double their weight they have to eat 400,000 eggs and if there aren’t enough horseshoe crabs, they don’t get enough to eat and they don’t have the energy to make these phenomenal flights.

Williams: OK, so why are horseshoe crabs becoming scarce?

Cramer: Why are they becoming scarce? For many years we’ve taken many too many of them to use as bait.

Williams: That sounds like a perfectly reasonable thing to do with a sea creature, but in fact horseshoe crabs are crucial to American medicine, right?

Cramer: They’re crucial to American medicine. Your life has been made better because of the blue blood of the horseshoe crab. If you have ever been vaccinated, or you know anybody who’s ever been in the hospital with an IV or IV antibiotics or medication, those medications and vaccines are safe for you because they’re free of dangerous bacterial contamination that is detected by a test made from the blue blood of the horseshoe crab.

Williams: But we know that, in for instance Cape Cod Bay, the horseshoe crabs are taken out, some little bit of blood distracted and then it’s a catch and release thing where they’re put back in.

Cramer: It’s a catch and release everywhere, but it’s not exactly a little bit of blood that’s extracted. It’s maybe as much as 30 percent. That’s a lot more than you give when you donate blood.

Williams: How does what we’re doing with the horseshoe crabs affect the red knots and other sea birds?

Cramer: The most important thing would be taking them for bait because when they’re taken for bait they’re chilled. And when too many are taken for bait, their numbers plummet. So it used to be that 90 percent of all the red knots in Delaware Bay would gain the weight they needed to fly to the Arctic and once the numbers of horseshoe crabs started dropping, the number of birds that gain the necessary weight also started dropping and dropped by as much as two-thirds.

Williams: How does climate change fit into this?

Cramer: Well, there are some regulations in place that have stanched the decline of horseshoe crabs. They’re not yet strong enough to rebuild the population so added on top of this are the upcoming threats of climate change. One of which is the accelerated erosion of the beaches. If the sand washes away, the horseshoe crabs won’t be able to come in and spawn as easily. Now the thing to remember is that horseshoe crabs have been following rising and falling seas for millions and millions of years. So if we’re able to give them a little breathing room and let the beaches migrate inland as the water rises they’re going to be fine.

Williams: We’ve been reporting about the expansion of oyster farming, commercial oyster farming, along the banks where the red knots refuel. It’s really their only refueling station on this continent. Is that squeezing them out?

Cramer: I don’t know the exact details of the oyster farms that you’re talking about. It seems that small, family-run oyster farms should be able to be on the bay with plenty of room for horseshoe crabs. Big, commercial applications that are going to be really enormous need to be sited in such a way that they are not impeding the arrival of horseshoe crabs on the beach.

Williams: What has to be done, do you think, to avoid extinction?

Cramer: In order to avoid extinction of the red knots we need to stop taking as many horseshoe crabs. We need to stop building bulkheads on our beaches so that as the water rises the sand can move inland. Basically, we need to give the birds safe passage that is food and sustenance and shelter on their long migration. It shouldn’t be that that hard for us to share the beach with others who’ve been dwelling here long before we have.