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DNREC says new report of big decline in rare shorebird is only a ‘snapshot’

Brian Kushner/Flickr

A spring survey showed a decline in the number of red knots stopping along the Delaware Bay during their annual migration.

Some see that decline as troubling and seek stronger measures to protect the shorebird and horseshoe crabs that provide the eggs they feed on.

But contributor Jon Hurdle reports not everyone sees this latest data as reason to act.

Delaware Public Media's Tom Byrne and contributor Jon Hurdle discuss concerns about red knot population numbers.

Delaware environmental officials say it’s too soon to conclude that the red knot, a shorebird, is back on the brink of extinction even though the latest count of the birds migrating through the Delaware Bay this spring shows the smallest number since records began almost 40 years ago.

The Department of Natural Resources and Environmental Control said the count showing only 6,880 of the birds’ rufa subspecies stopped off on both the Delaware and New Jersey sides of the bay this season was only a “snapshot” that doesn’t account for the bay’s total population.

"I think it's reasonable to wait and see what the rest of the data says. But the fact remains that we;ve been doing a count since the 1980s when it was up around 90,000 and now it's down to 6,800."
Biologist Larry Niles

DNREC didn’t release its own estimate, saying it’s still working with other state and federal agencies to  evaluate this year’s data, but argued that the horseshoe crab eggs that sustain the birds on their long migration from South America to the Arctic were plentiful on the bay beaches this year, and that reports from South American wintering grounds indicated a stable population.

That’s at odds with an assessment from Larry Niles, a veteran biologist who has been monitoring the birds’ migration from the New Jersey side of the bay for the last 25 years.

Niles’s count – which includes knots stopping on the Delaware side – found the bird’s numbers this year unexpectedly plunged to only about a third of that in 2020 and less than a quarter of that reported for the previous two years.

In the early 1980s, the number of red knots migrating through Delaware Bay each spring was around 90,000. Combined with larger numbers of several other species, the knots made Delaware Bay the setting for one of the world’s great shorebird migrations, drawing scientists and volunteers from all over the world to sites like Mispillion Harbor in Sussex County.

Last year, crab spawning was delayed because of unusually cold ocean temperatures when migration was underway. That meant many birds arriving at the bay after continuous multi-day flights were unable to find the crab eggs that would enable them to regain weight and complete their migration. Many pressed on but an estimated 40 percent died en route from the Delaware Bay to Arctic Canada simply because they ran out of energy, Niles believes.

Last year’s presumed mortality during migration sharply reduced the number of birds that bred successfully, leading to the much lower numbers seen in this year’s northbound migration, Niles said.

The latest numbers suggest a sharp setback to a quarter-century of conservation efforts, and renewed fears that the species is now too scarce to survive shocks like bad weather in its Arctic breeding grounds, or real estate development at stopover points during the migration – which at up to 10,000 miles is one of the longest in the avian world.

Niles says the new decline argues for a bay-wide ban on the harvest of female horseshoe crabs so that the birds have plenty of food to eat, allowing crabs, birds and the bay’s whole ecosystem to recover.

This year, crab spawning was plentiful but in the long term, the density of their eggs on the beaches has been much lower than it needs to be for the birds to rebuild their population, and remains so, Niles said.

But DNREC rejected the notion that conditions on the Delaware Bay are the main threat to the birds’ survival.

“In the view of our wildlife protection agency, the current horseshoe crab population and egg abundance in the Delaware Bay available to spring migrating red knots is not a limiting factor to red knot population size,” said spokesman Michael Globetti, in a statement.

Rather, he said, the species is threatened by climate-related factors in Arctic breeding grounds including the timing of snow melt and the availability of prey. The rufa red knot, weighing only 4.7 ounces when mature, is listed as threatened by the federal government.

Migrating red knots have seen their number dwindle since the 1980s

Although the estimate published by Niles and his colleagues is lower than in recent years, it is based on a survey that takes place on only one day, in contrast to the five-week migratory season during May and early June, Globetti said.

The red knot, other migratory shorebirds, and the horseshoe crabs they depend on, have been the focus of strenuous conservation efforts on both sides of the bay for years. At Mispillion Harbor, a migration hotspot, conservationists have recently completed the transfer of protected lands to DNREC in an effort to permanently provide optimal habitat for the birds. On the New Jersey side, the crab harvest has been banned altogether by state law since 2008, and some beaches are closed to the public during migration.

By the decade beginning in 2010, the conservation measures appeared to have halted an earlier decline, and perhaps set a foundation for rebuilding the population. But the big drops of the last three years appear to show that the sub-species is once again close to extinction.

Conservationists say the latest drop in knot numbers amplifies their long-held call for a bay-wide ban on the harvest of female horseshoe crabs.

But DNREC’s Globetti noted that Delaware harvests only male crabs, according to a quota set by the Atlantic States Marine Fisheries Commission since 2014. The quota system allows Delaware fishermen to catch about 162,000 crabs each year, and that policy has sustained the ratio of male to female horseshoe crabs without disrupting the production of eggs, he said.

"The current horseshoe crab population and egg abundance in the Delaware Bay available to spring migrating red knots is not a limiting factor to red knot population size.”
DNREC spokesman Michael Globetti

Delaware issues permits to 31 parties who are allowed to harvest crabs by hand from June 8-July 31 each year, after the migratory birds have left the bay. If the quota is not filled through the hand harvest, the state issues five horseshoe crab dredge permits through a lottery.

“Harvest is reported daily and closely monitored so as to close the fishery before the harvest quota is exceeded, and DNREC’s Delaware Natural Resources Police closely monitor horseshoe crab harvest compliance,” he said. “The agency does not believe that Delaware’s horseshoe crab fishery is negatively impacting the red knot population we are charged with helping to protect.”

Crabs harvested off Delaware are used for bait by the fishing industry. The state, which enforces the commission’s quotas, does not allow crabs to be harvested for the biomedical industry, which uses blood from crabs to extract LAL, a clotting agent that detects bacteria in vaccines and other medical products.

So-called bleeding companies extract about 30 percent of each crab’s blood, and then return the animals to the ocean, according to Tina Berger, a spokeswoman for the fisheries regulator. It assumes that 15 percent die in the process, a number that’s disputed by conservationists who say the mortality rate could be closer to 30 percent.

According to the commission, some 589,000 crabs were bled by the biomedical industry in 2019, and about 101,000 died because of the process.

But mortality among crabs taken for bleeding is less than for other uses, and so the commission’s Horseshoe Crab Management Board “has not found restrictions on the biomedical harvest are warranted,” Berger said.

But conservationists say that any mortality at the hands of the biomedical industry is unnecessary because there’s a readily available and effective synthetic alternative, known as rFC, that could be used by the pharmaceutical industry as a whole if it was officially endorsed as a substitute for LAL by USP, a trade group that sets industry standards.

Credit Katie Peikes / Delaware Public Media
Delaware Public Media
Eggs from spawning horseshoe crabs found on on Delaware Bay beaches help sustain red knots on their long migration from South America to the Arctic

USP has been under pressure to quickly endorse rFC, an act that conservationists say would slash demand for the crab-based product, and become a key move in rebuilding the crab population. But USP has not yet done so, and is now preparing to begin a study that compares the two substances.

Still, the trade group says that companies can make their own decisions to switch to the synthetic material – as the pharma giant Eli Lilly has done – while the USP study proceeds.

“When companies make a commitment to rFC, not only do they live up to expectations the public has for minimizing their environmental impact, but they also contribute to data that can move rFC to be considered interchangeable with LAL,” said Anne Bell, a spokeswoman for the group.

From Niles’s point of view, DNREC can wait to receive more data before drawing conclusions about the status of the knot’s population, but that won’t change the fact that numbers have plummeted, and may now be below the level where the species will survive.

“I think it’s reasonable to wait and see what the rest of the data says. But the fact remains that we’ve been doing a count since the 1980s when it was up around 90,000 and now it’s down to 6,800,” he said. “People can argue all they want about new data but that’s the fact.”

Jon has been reporting on environmental and other topics for Delaware Public Media since 2011. Stories range from sea-level rise and commercial composting to the rebuilding program at Prime Hook National Wildlife Refuge and the University of Delaware’s aborted data center plan.
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