Red knots—the plump, rust-colored shorebirds that flock to mid-Atlantic beaches each spring—are a federally threatened species, but new research suggests they may be on the rise. This year, the species’ numbers on Delaware Bay coasts have grown to a four-year high, according to an independent annual survey. The uptick may be good news for the species, after its bay population hit a historic low in 2021.
“I was elated to see 22,000 birds this year, and almost all the red knots came to Jersey. I consider that a win,” Larry Niles, a biologist who leads a bird-counting team, tells NJ Spotlight News’ Jon Hurdle. “We’re trying to improve conditions on our side of the bay, and the birds coming back are evidence of that.”
Red knot shorebirds stop in the bay during their annual spring migration to their summer breeding grounds in the Arctic. Some of the birds come from as far away as Tierra del Fuego off the southernmost tip of the South American mainland, flying more than 9,000 miles in total, one way. This is one of the longest-distance migrations in the animal kingdom.
The birds’ arrival to Delaware Bay overlaps with the yearly horseshoe crab spawning. The migrants pause in the region, famished and nearly half their starting weight, to spend about a month scarfing down crab eggs to power them through the last leg of their journey.
“They arrive here, and they really need to build up their weight,” Joanna Burger, a behavioral ecologist at Rutgers University, tells WHYY’s Mark Eichmann. “They arrive at about 100 grams [3.5 ounces]. And in the two or three weeks that they’re here, they will almost double their weight. And that is possible because of the abundance of horseshoe crab eggs when they’re in Delaware Bay. That is all they eat.”
But horseshoe crab numbers are declining. The marine critters are valuable commodities for fishermen, who use them for bait, and the biomedical industry, which harvests their unique blood to detect toxins in medical products.
Historically, the birds’ numbers in the bay hovered around 90,000 in the 1980s, writes the New York Times’ Jon Hurdle. In 2021, their numbers hit a record low of 6,880. In some areas of the Atlantic Coast, red knots have declined by an estimated 94 percent since 1980. In 2014, the U.S. Fish and Wildlife Service (USFWS) granted the birds federal protection, attributing their decline to habitat loss, reduced food availability and possible increases in predation.
Of the 22,000 birds counted this year, about 20,000 were seen on the New Jersey side of the bay, which signals that the state’s efforts to protect the birds, including beach closures, habitat restoration projects and a 2008 moratorium on horseshoe crab harvesting, are having their intended effect, per NJ Spotlight News. The harvest of female crabs has been banned in the bay since 2013, but males can still be collected in Delaware—and experts suspect that females are caught there, too, due to a lack of enforcement.
“Delaware’s continuing bait harvest is taking its toll on the horseshoe crab population that uses the Delaware Bay shore for spawning,” Steve Cottrell, president of Delaware Audubon, tells the Times.
Further, the annual red knot population estimate from the U.S. Fish and Wildlife Service, which relies on modeling, differs from these new numbers, which complicates conservation efforts, per the Times. The service maintains that the numbers in the bay have remained steady at around 42,000 over the last four years, but Niles tells the Times that the agency’s methods result in inflated numbers.
Still, increased protections for wildlife in the Delaware Bay area could be both environmentally and economically beneficial, as large populations of red knots tend to attract birders who are eager to observe them.
“As climate change continues to imperil important habitat along the red knots’ migration route, it is our shared responsibility to conserve Delaware’s natural beauty, which attracts more than wildlife,” United States Senator Tom Carper of Delaware said in May, per WHYY. “Tourism in Delaware, including birding and other nature activities, contributes nearly $4 billion to our economy annually. … It’s a win-win when we work together to protect our natural resources like our red knots.”