Every May on the Delaware Bay, researchers from South Jersey to Australia spend several weeks catching migrating shorebirds to learn more about them, and why some are disappearing.
The bay is a primary refueling stopover. In one of nature's most elegant moments of timing, the birds arrive just as horseshoe crabs emerge from the bay to lay their lipid-rich eggs in the sand.
Because the birds congregate so tightly, the bay offers one of the few places along the flyway - from the tip of South America to the Canadian arctic - where researchers can hope to catch them.
The bay draws the researchers as surely as it does the birds. Many, like England's Humphrey Sitters, a lawyer who later studied shorebirds for his doctorate at Oxford, are volunteers who have come for more than a decade.
Then there are Anneke and Jack Mace, New Zealanders who heard about the effort and came last year on their honeymoon. Now, they're back.
Cheryl and Dan Alexander of Audubon are volunteer "stewards" who station themselves near beaches that are closed - to avoid disturbing the birds as they feed - to explain the bird-and-crab phenomenon to visitors
Brazilian scientist Anna Paula is studying contaminants in shorebirds.
Minton, a British metallurgist by trade and a shorebird researcher by passion, is a bird-netting pioneer who has been at it since the early 1950s.
Minton, who now lives in Australia, adapted large nets used to catch geese. In the current versions, weights propelled by small cannons launch the net over the birds.
The secret to netting, said Minton, who has been coming to the bay for 18 years, is good reconnaissance. Every morning, he and Niles go out to assess miles of beaches, learning where the birds congregate at high tide. Later, they'll know where to place the net.
For now, though, the birds were too far south.
Breep! Niles, a Cumberland County shorebird expert who used to head the state's Endangered and Nongame Species Program, radioed Joe Slusher, part of a University of Georgia team studying bird influenza.
It was time to "twinkle" the flock. Slusher, stationed farther down the beach, took a careful step toward the birds and stopped. He took another step. Gradually, the birds began to move away from him - and toward the net.
The goal Monday was sanderlings, tiny shorebirds that some liken to windup toys because of the way they skitter among the waves.
The researchers also target ruddy turnstones and red knots - a subspecies in such sharp decline that it has been proposed for listing as an endangered species.
Biologists blame the decline on not enough crab eggs due to an overharvest of horseshoe crabs, which are used as bait to catch conch and eels, delicacies in Asian markets.
New Jersey now prohibits the crab harvest; other states limit it.
Just as it seemed crab numbers were poised to rise, the bay-shore beaches where they lay their eggs were scoured by Hurricane Sandy. More than $1 million has been spent to restore them. U.S. officials are considering a $5 million proposal to do more.
As Slusher took one step, then another, the researchers saw another problem: Too many birds were too close to the net - a danger zone where they might be hit by it.
From his hiding spot, Minton jiggled a line laid in front of the net. He wanted to make the birds move away, but not scare them into taking flight.
In an instant, the birds were in the right place.
"Three, two, one, fire!" Niles yelled. The cannons boomed and the net unfurled, trapping about 220 sanderlings underneath it.
A good catch.
For the next several hours, they put ID bands on the birds' legs so they could be spotted and identified later. They weighed the birds and measured their beaks and wings.
The Georgia team headed out to find ruddy turnstones and collect fecal matter that will be analyzed for viruses. The results will be added to a database available to scientists worldwide.
Unlike the red knots, sanderlings aren't in decline. But the researchers have begun collecting data anyway, in case it's needed. "It's a resource that's always there," Niles said.
That strategy has already panned out for the turnstones, which researchers now realize are also in a severe downslide.
Why? "That's a big new question," Minton said.
And so Niles and the others who began trapping on the bay nearly two decades ago will keep at it.
"I'm going to trap until I die," Niles said.