A conservation success story: American oystercatchers, resilient shorebirds, nesting on New York beaches

It was the tail end of the breeding season for American oystercatchers, a quirky-looking shorebird that breeds on New York beaches from Rockaway Point to the East End. Field biologist Emilio Tobón raised his binoculars and slowly scanned the zone above the high-tide line in Breezy Point.

There were plenty of adults strutting among the grasses and low-growing bayberry, but it was harder to find their chicks. Finally in the distance he spotted a hatchling darting after its parents, pale downy feathers camouflaged against the sand.

That one chick, small enough to fit in a teacup, is part of a notable conservation success story. Of more than two dozen North American shorebird species, a 2023 study found more than half had declined by 50% or more in the past 40 years. Yet after a period of decline, American oystercatcher populations all along the Atlantic and Gulf Coasts are now increasing.

Their recovery offers encouraging evidence that some species under certain conditions are able to adapt as their environments change. 

More than a dozen Long Island beaches

American oystercatchers are easy to identify, with their black or dark brown and white plumage, bright orange bills, red-rimmed eyes and long pink legs. They inhabit Atlantic Ocean shores from Massachusetts to Florida; they can also be found on the Gulf Coast and in the Caribbean and Central and South America.

Oystercatchers nest on more than a dozen Long Island beaches; the largest sites are Lido Beach, Point Lookout and Jones Beach, according to Shelby Casas, the coastal program manager for Audubon New York. But about 65% of the known oystercatcher population in New York State breeds on New York City beaches.

Oystercatchers are highly “site-faithful,” Tobón, of the NYC Bird Alliance, said Monday. Though a breeding pair may separate for the winter, they return year after year to the same beach, generally reuniting with the same mate. They often nest near endangered piping plovers. “The oystercatchers usually arrive first,” Tobón said, alighting in New York in mid-April, “and then the piping plovers. But they’re always neighbors.”

They lay two to three eggs in a shallow scrape in the sand, sometimes lining it with shells or pebbles. After about a month, the chicks emerge; 30 to 45 days later they are able to fly. Both parents continue to feed the fledglings for at least another month, until they can forage on their own.

For nearly 15 years, Tobón has been monitoring nests on the Rockaway Peninsula, in the Gateway National Recreation Area, heading out twice a week during breeding season to count eggs and chicks. About 10 years ago, his research showed the number of hatchlings was declining — but he wasn’t sure why. He suspected predators were raiding the nests and eating the eggs, so to test his hunch, the NYC Bird Alliance set up motion-sensing trail cameras near oystercatcher nests.

Researchers collected hundreds of thousands of images from two dozen nests in multiple sites and — with the help of an AI program trained to identify birds and mammals known to steal eggs — they discovered the thieves. “Lots of cats,” Tobón said, probably mostly feral but perhaps also owned cats allowed to roam outdoors. Raccoons and opossums were the next most common predators.

Gulls, previously a leading suspect, were more likely to scavenge abandoned, nonviable eggs, researchers learned.

There was no obvious answer to the problem. “Symbolic” fencing — wires strung between posts marked with colored ties — has been used for many years to alert beachgoers to nesting areas. But the fencing provides no deterrence against cats or raccoons.

Happily, the birds themselves worked out a solution. A female who loses her first eggs will lay a second clutch. If she loses those, she will lay a third time. Occasionally, she will try a fourth time.

“We found the birds can adapt,” Tobón said. “If they have the flexibility to make several attempts, in that way, they are sometimes successful.” Oystercatcher numbers started to stabilize by 2019, and then to slowly rise.

The birds have also been rebounding throughout their range on the Atlantic and Gulf coasts, aerial surveys show. Between 2001 and 2023, their populations increased 43%, according to Alan Kneidel, a conservation biologist with Manomet Conservation Sciences, based in Plymouth, Massachusetts.

On Long Island, oystercatcher populations have been gradually increasing overall since 2019, Casas of Audubon New York said, though some local populations are faring better than others. Nest failure is common in the Peconic Estuary, largely because of predation, according to Jennifer Murray, the shorebird manager for the Town of Southold. But oystercatchers that nest on a tiny island in the bay (Murray declined to say where, to protect the birds), where there are fewer predators, are successfully fledging chicks.

The total numbers are still small — the 2023 estimate for American oystercatchers on the Atlantic and Gulf coasts was fewer than 15,000 — but researchers hope the recovery will continue.

The NYC Bird Alliance is just one of dozens of local and national conservation groups that have been collaborating under the umbrella of the American Oystercatcher Working Group, monitoring nests, identifying threats to the birds' survival and developing strategies to protect them.

More than 6,000 birds in the United States and Mexico — including oystercatchers that nest on Lido Beach and Point Lookout — have been fitted with numbered leg bands that can be read by anyone with a good telephoto lens. With more than 75,000 sightings in the past 25 years, ornithologists now have a clearer picture of oystercatchers' migration habits, which might take them from Long Island in the summer to Florida in the winter.

Last year, a bird that hatched and was banded in the Rockaways was observed in El Salvador, according to Tobón.

“Over the years, all those sightings have really accelerated our understanding of how the oystercatchers are using the coastline,” Kneidel said. Now scientists are working to protect oystercatchers’ important wintering grounds and stopovers ”to support their journeys.”

New York City shorebirds contend not only with predators but also with thousands of beachgoers, who may not always keep a respectful distance. In one of the camera trap photos, a volleyball game was underway right next to nesting oystercatchers.

“It’s not an easy life for these birds,” said Dustin Partridge, director of conservation and science for the NYC Bird Alliance. But “I think there is something really stunning about these birds and their ability to survive in New York City,” he added. If it can happen here, he said, “it can happen anywhere.”