Rising seas endanger Long Island marsh bird habitats

 Saltmarsh sparrows build their tiny nests in the dense grasses of the marsh and hide them so well that Nicole Maher, who has been studying coastal wetlands and their inhabitants for nearly 20 years, has never spotted one on her own.

The sparrows are endemic to the marshes on the East Coast — they exist nowhere else in the world. But those habitats and the birds that depend on them are quickly disappearing, in part due to the effects of a heating planet, according to experts.

As seas rise, the salt marshes, already just fragments of the great expanses of wetlands that once fringed the shorelines, are becoming inundated by higher tides and storm surges, which are flooding out the sparrows’ nests.

“With the loss of high marsh habitat and increased rate of flooding of our coastal marshes, these birds’ numbers are going down across their whole range,” said Maher, a senior coastal scientist at The Nature Conservancy in New York. 

 The population of saltmarsh sparrows has declined by 87% in the past 25 years, from about 212,000 in 1998 to roughly 20,000 today, based on the U.S. Fish and Wildlife Service's projections. Experts fear they could be extinct by the 2050s without intensive conservation efforts. If they do disappear, they could be the first casualties of sea level rise. 

The federal government is considering listing the saltmarsh sparrow under the Endangered Species Act, which would offer extra protections to the birds and their habitats. A decision is expected in September. But Javier Lloret, an ecosystem scientist at the Marine Biological Laboratory in Woods Hole, Massachusetts, is not optimistic about their prospects.

“I don’t see much of a future for these types of environments — for the salt marshes and for the species that are so dependent on a narrow band of the marsh to exist, like the sparrow,” Lloret told Newsday. He and other researchers at Woods Hole estimate that 90% of the world’s salt marshes could be underwater by the end of the century.

Long Island conservation groups are working to prevent that grim future, monitoring chick survival rates at local preserves and state parks and restoring degraded salt marshes to improve the birds’ critical nesting habitat.

Disappearing habitat

A small dark-eyed saltmarsh sparrow, held in Sam Apgar’s gentle grip, blinked quickly but did not struggle as the scientist measured her wing, her delicate leg bone and her beak. Apgar, a wildlife biologist with the U.S. Fish and Wildlife Service, blew gently on the bird’s belly, revealing a brood patch, a featherless area that helps females transmit body heat to their eggs.

The spot of wrinkly pink skin was good news to Apgar and the other researchers gathered in the early morning at Pine Neck Sanctuary in East Quogue. It meant that somewhere nearby, she had built a nest amid the dense grasses and laid a clutch of eggs; and in a few days, if all went well, she would be tending to hatchlings.

Saltmarsh sparrows look for nest sites near enough to the boggy low marsh to discourage predators such as foxes and raccoons from raiding their nests, but far enough from the sea to avoid daily high tides.

“They are very particular,” Maher said. The females “cue in” on the type of grasses that grow in this narrow zone, which floods just twice a month, during the spring tides at the new moon and the full moon.

It’s a precarious existence. “Their first nests tend to get washed out by high spring tides,” Apgar said. They immediately lay a second clutch, this time “synced” with the lunar cycle, “so they can fledge their chicks before the next-highest tides.”

That careful timing is no longer enough to keep their nests safe. All along the East Coast, salt marshes are becoming inundated by rising seas. As the daily high tides creep farther inland, eggs are floating out of their nests and hatchlings too young to scramble to higher ground are drowning. These nest failures are the leading cause of the saltmarsh sparrow’s decline, according to the Fish and Wildlife Service.

In theory, marshes can migrate inland, and in some areas on Long Island, low marsh grasses are moving into the high marsh. But the plants of the high marsh often have no place to go. It is a problem that Lloret calls the “coastal squeeze”: The sea is encroaching from one side, and roads, houses and other structures create a barrier to migration on the other. Marshes “cannot go through someone’s backyard or a built structure like a sea wall,” he said.

Under good conditions, sediments deposited on the marsh floor allow it to rise in elevation, but Maher’s investigations since 2008 in salt marshes across Long Island show seas are rising too fast and the marshes have not been able to keep up.

As the wetlands disappear, so do the many benefits they provide to humans and other animals: They provide habitats for birds, shellfish, crustaceans and finfish. They protect shorelines from erosion and flooding by dissipating the force of waves, absorbing rainwater and trapping sediment. And their soggy soil sequesters vast amounts of carbon — many times more per acre than a tropical rainforest. 

Saving marshes to save the sparrows

On a bright day in early June, three great egrets were foraging in the mud flats in the salt marsh at Sunken Meadow State Park on Smithtown Bay. A juvenile osprey peered over the edge of a nest built on a high platform and a red-winged blackbird called from somewhere in the reeds. But saltmarsh sparrows have not nested in this park for some time, according to Victoria O’Neill, director of coastal resilience at Audubon New York, a nonprofit conservation group.

Parts of the wetlands were paved over for parking lots in the 1920s; later, ditches drained more of them for mosquito control, and in the 1950s, an earthen berm built across Sunken Meadow Creek blocked the incoming tides, profoundly altering the ecology of the marsh.

The berm collapsed during Superstorm Sandy in 2012, reconnecting the marsh to the natural tides, which inspired a multimillion dollar effort to restore a healthy saltwater marsh. Audubon and its partners — New York State Parks, Save the Sound and the New York Natural Heritage Program — are focused on expanding and improving the park’s 9 acres of high marsh habitat.

Old mosquito ditches will be filled in to improve the marsh’s hydrology and sediment added to the high marsh areas, methods Audubon already has tested in Great Meadows Marsh near Bridgeport, Connecticut. “They made areas of higher elevation inside the marsh” to build a wider safe zone for the sparrows, “and they found they are actually starting to use those, so it worked,” O'Neill told Newsday.

At The Nature Conservancy’s preserves at Accabonac Harbor in East Hampton, mosquito ditches will be filled in with bundles of marsh grass and shallow rivulets built to restore the marsh’s natural hydrology and sediment flow.

“For hundreds of years we’ve been modifying the hydrology, the way the water moves into and out of these marshes,” Maher said. The Nature Conservancy’s restoration work aims to undo the damage “so the marsh can grow and keep pace with sea level rise.” 

Back at Pine Neck, Apgar was focused on safeguarding the future of just one saltmarsh sparrow. She worked quickly, mindful that the little bird had eggs hidden nearby. “Females provide all the parental care,” she said. “Females build the nest, lay the eggs, incubate the eggs, feed the chicks, fledge the chicks and keep feeding them for another two weeks until they're flighted and can feed themselves. So, she's a busy lady.” 

Apgar clipped an aluminum tag on the bird’s leg, so if scientists catch her again, they will know something of her history. She walked a few steps away from the cluster of researchers and slowly opened her hands. The bird hesitated for a moment, then flew away over the marsh.