A Conservancy scientist takes the measurements of a red knot before releasing it. The Conservancy's Virginia Coast Reserve (VCR) is a key stopover site for migratory red knots. © Barry Truitt

Counting Red Knots

Keeping Tabs on a Threatened Bird

Geolocators. Nanotag radio transmitters. Solar-powered satellite tags.

The technology for tracking wildlife gets fancier every year. But, sometimes, it pays to be old school.

For two decades, researchers at The Nature Conservancy’s Virginia Coast Reserve (VCR) have been counting rufa red knots and other migrating shorebirds the old-fashioned way: one bird at a time.

Counting Since 1995

In 1995, Barry Truitt, former chief conservation scientist at the reserve, and Bryan Watts, director of the Center for Conservation Biology of The College of William and Mary and the Virginia Commonwealth University, began counting migrating shorebirds in the Virginia barrier islands — one by one — from a low-flying Cessna 172.

“This area is globally important to shorebirds, and nobody had a handle on what was going on,” Truitt says.

The method may be low-tech, but the population surveys contributed valuable data to the U.S. Fish and Wildlife Service as it considered the conservation status of the rufa red knot.

Between the 1980s and the mid-2000s, the knot population in the western hemisphere fell from 100,000-150,000 birds to fewer than 33,000. In January, the agency listed the red knot as a threatened species under the Endangered Species Act.

Robin-sized with slender legs, the cinnamon-colored rufa red knot is a delicate-looking bird. Looks are deceiving.

“They’re capable of these incredible long-distance flights,” says Watts.

A flock of red knots take flight over the Atlantic shoreline of the Eastern Shore. The Conservancy's Virginia Coast Reserve (VCR) is a key stopover site for migratory red knots. © Barry Truitt
A flock of red knots take flight over the Atlantic shoreline of the Eastern Shore. The Conservancy’s Virginia Coast Reserve (VCR) is a key stopover site for migratory red knots. © Barry Truitt

Some knots migrate more than 9,300 miles along the Atlantic coast, from summer breeding grounds in the high Arctic to winter retreats as far south as Chile and Argentina.

For a few weeks each spring, the birds stop along the mid-Atlantic coast of the U.S. to fatten up. As a “terminal staging area,” the region is key to the red knot’s success, Watts explains. “It’s the last place they refuel before they make their final flight to the Arctic breeding grounds.”

Once a week during that stopover, Truitt and Watts flew the length of the barrier islands’ outer beaches. Flying just 25 to 30 meters above the surf to flush foraging shorebirds into the air, Watts noted species and tallied flock sizes while Truitt marked their locations on aerial photos.

Discovery: Virginia is a Red Knot Hot Spot

They conducted their first surveys in 1995 and 1996, and from 2005 through 2014 the aerial tallies were an annual event. Though Truitt is recently retired from the Conservancy, Watts plans to continue the bird counts into the future.

Before those surveys, Virginia wasn’t recognized as a red knot hot spot.

“For a long time, the scientific community focused on Delaware Bay as this standalone critical staging area for red knots,” says VCR scientist Alexandra Wilke.

Red knots famously stop by Delaware Bay, home to the world’s largest spawning population of horseshoe crabs, to feast on the crab-egg bounty each spring. But Watts and Truitt showed that the Virginia barrier islands host the second-biggest concentration of migrating knots in the nation.

Horseshoe crabs wash up along the shores to spawn and lay eggs around the new and full moons. Photo © 2012 Erika Nortemann/TNC
Horseshoe crabs wash up along the shores to spawn and lay eggs around the new and full moons. Photo © 2012 Erika Nortemann/TNC

That’s good news for the knots since almost the entire Virginia barrier island lagoon system is protected by conservationists. “In the midst of the chaos and craziness of what we’ve done to the Atlantic coast, we have this oasis of undisturbed habitat,” Wilke says.

Still, the birds are disappearing, and they face a growing horde of hazards throughout their range.

The commercial horseshoe crab harvest has shrunken the knots’ food supply in Delaware Bay.

And in Virginia, where knots feed on mussels and clams, certain mussel populations have been shifting northward each year as ocean waters warm.

The Virginia Coast Reserve is now at the southern edge of those mussels’ range. Soon, that food source may disappear completely from the safe haven of the Virginia barrier islands.

Competition for Habitat

The undeveloped beaches at the Conservancy's Virginia Coast Reserve are important habitat for migratory birds, including red knots. © John M. Hall
The undeveloped beaches at the Conservancy’s Virginia Coast Reserve are important habitat for migratory birds, including red knots. © John M. Hall

Elsewhere, shorebirds find steep competition for habitat along beaches popular for recreation. And then, of course, there’s the fast-changing Arctic—the only place where red knots breed. Climate change could alter the birds’ nesting habitat, reduce food availability, and even make predators more likely to prey on visiting shorebirds.

So far, Truitt says, there’s been relatively little research on red knots in the Arctic. That will need to change.

“It doesn’t do any good to have wild beaches in Virginia if something is killing them up in the Arctic,” he says.

To save these troubled shorebirds, scientists will have to take a deeper look at the entire red knot range, from one end of the Earth to the other. They will need all the tools on the table—low-tech, high-tech, and everything in between. — NCM

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