Attacked from all sides: waders nest on New York’s Harbor Islands

For bird lovers and the average citizen alike, the sight of wild, colorful migratory birds like the great egret or the night heron in a dense and noisy city like New York is something very special.

Each spring, these wading birds migrate to uninhabited islands along the city’s coastline, as well as to certain areas on the city’s mainland, to breed and forage. For the past four years, Shannon Curley, a postdoctoral fellow at Cornell University, has traveled to these islands to coordinate the New York City Bird Alliance’s annual survey of nesting herons.

“When you stand on one of these islands,” Curley said, “you can see hundreds of nesting birds on your right and the New York City skyline on your left. It’s a completely unreal experience.”

Since 1985, the Bird Alliance has continuously monitored the nesting habits of 10 species of waders that emerge each spring and worked to conserve their habitats long-term. In May 2022, they even observed the more reclusive Great Blue Heron nesting on an island in the East River called Mill Rock—the first confirmed nest in New York County.

“Every time we go out there and see them,” said Dustin Partridge, director of climate and resilience at the New York City Bird Alliance, “I’m still amazed that they are literally dinosaurs. There are dinosaurs living in New York Harbor.”

The fact that the survey has been conducted for a long time does not dampen the enthusiasm of those who conduct it.

Although their nesting habits likely existed before the city of New York in its current form, these shorebirds face ongoing habitat loss due to coastal development, human disturbance, predation, and sea level rise. Their health and behavior can also be affected by pollutants or contamination in local waterways.

Currently, these waders nest on six of the many small, uninhabited islands along the city’s coast. Although they can adapt to a small human presence, human encroachment into their territory can cause entire colonies of waders to abandon an island or not return to it the following year.

“It’s important to avoid islands where there are signs for nesting birds,” Curley said. “We don’t want to lose the colony just because one person decided to have a campfire on an island.”

Humans can also have indirect effects on these bird populations. According to the bird conservation organization, there are unintended consequences when residents release predators like raccoons into green spaces along the coast. Raccoons are known to swim to islands within reach and prey on smaller waders and their chicks. Birds like snowy egrets and ibises often nest in shrubs closer to the ground, making them more vulnerable to these types of predators.

Two years ago, herons left Subway Island in Jamaica Bay, primarily due to the presence of raccoons.

“It was once the most biodiverse and diverse island in Jamaica Bay,” Partridge said. “When we arrived in 2022, everything was quiet – there were no birds there. All that was left were lots of raccoon tracks and droppings and a few gnawed carcasses.”

Human disturbance and increased predators may threaten the habitat of these bird species, which are already severely impacted by the development of urban coastlines for industrial and residential purposes. If birds permanently lose safe nesting sites, this may impact their population numbers.

“If their reproductive efforts are unsuccessful year after year, you may actually be losing birds,” says Joanna Burger, a behavioral ecologist at Rutgers-New Brunswick University. “A heron will raise only one chick for several years instead of three, and that reduces the overall population – even if the colony still exists – because fewer and fewer young birds are entering the breeding population.”

These waders are also exposed to potential contamination of their food supply. They are apex predators – eating everything from fish to crustaceans, amphibians and rodents. This also means they are important indicators of the health of the harbor.

“In 70 years, we’ve changed the environment along the Jersey and Long Island coasts,” Burger said. “That’s not a lot of time to change the environment for breeding birds that have lived on the coast for thousands of years.”

Herons did not return to New York’s harbor islands until after the passage of the Clean Water Act of 1977. Heavy metals can build up in herons’ blood, eggs and feathers, negatively affecting their behavior and alerting ecologists like Burger, who study them, to pollutant levels in local waters.

Today, metal contamination is less of a concern because lead and cadmium levels in these birds have steadily declined over the past half century, says Burger. The reason for this is mainly new regulations on the use of these metals in paints and batteries.

Since the turn of the century, mercury levels in birds have not declined at the same rate due to emissions from coal-fired power plants around the world. Mercury is a “global pollutant,” meaning it can travel many miles through the atmosphere before being deposited on Earth, often through rain.

In April, the Biden administration released final changes to the Mercury and Air Toxics Standards (MATS) that could lead to a reduction in mercury emissions from power plants in the United States.

“You could say that the impacts of pollutants are small compared to the impacts of (habitat) fragmentation or habitat loss,” Burger said. “And while that’s true, it’s still important to reduce all possible negative impacts, because some of them we can’t.”

According to the bird conservation organization, these birds have been observed foraging as far away as Yonkers, 14 miles north of Midtown Manhattan, to feed themselves and their chicks. When beaches, marshes and wetlands are developed for other uses or are lost to erosion, wading birds lose access to food.

In recent years, the New York City Parks Department, in collaboration with the Natural Areas Conservancy, has initiated projects to restore marshes and wetlands along the city’s coast, creating important foraging opportunities for shorebirds and nesting sites for migratory birds.

Another urban shoreline, the New Jersey Meadowlands, the system of wetlands and marshes that line the Hackensack River, is a few miles west of New York City. The black-crowned night heron and the yellow-crowned night heron have been observed here since ecological restoration and conservation work began. These bird species are considered threatened in New Jersey, but not in New York, which Partridge regrets.

According to Teresa Doss, co-director and chief restoration scientist at the Meadowlands Research and Restoration Institute, three-quarters of the Meadowlands’ 20,000 acres have been lost to development, largely due to industrial and residential uses and landfills.

“We have all these areas that are filled with swamps, but they’re open spaces,” Doss said. “We see that if you just leave nature alone, it will automatically come back. We’re looking at how we can help restore these dumping grounds and create habitat systems that provide shelter for many migratory bird species.”

The Meadowlands Institute is considering introducing artificial coral reefs, called Reef Balls, to support marine life while limiting erosion of marshes along the coast. Restoring and strengthening wetlands and marshes along the urban coast is paramount not only for breeding grounds for herons, which require elevated elevation to survive storm surges, but also for the continued human presence. Wetlands provide important flood protection for coastal communities, especially as sea levels rise and rainfall increases due to climate change.

“When you think about the natural infrastructure here, you think about the wetlands that filter the water and mitigate the floods,” Doss said. “You think about the forests and grasslands that can sequester carbon and help clean water and rain.”

Restoring wader habitat also means better protection from flooding for coastal communities.

Even urban coastlines that have a long history of environmental degradation and commercial and industrial development can still support an incredibly diverse range of migratory bird species. While it is unlikely that coastal communities will cede their territories to the birds that once nested and foraged freely along Hudson estuaries, coexistence seems possible.

By comprehensively restoring the remaining green spaces along the coast and in the bay, and limiting human interference with shorebird nesting areas, these wild shorebirds will be able to continue their annual pilgrimage to the city’s shores.

“Imagine the wild coasts of Maine, or the beaches of Cape Cod, or any of these wild places in the Northeast,” Partridge said. “When you consider that New York City has this wader population that doesn’t exist there – this area that has this high density of waders – it’s kind of magical to me.”