Blame climate change — and maybe rats — if this Jersey shorebird goes extinct

For one of New Jersey’s most extraordinary birds, climate change means much more than stronger storms and higher water. Researchers at the University of Delaware have found that, due to flooding, habitat destruction, and predators, the saltmarsh sparrow could vanish from the state within 20 years.

While similar in size to the house sparrows that are common throughout the country, the saltmarsh sparrow is found only along the Atlantic Coast. With striking orange markings on its head and chest, it is quite handsome. And this sparrow has adapted to an extreme environment — the saltwater marshes from which it gets its name.

"We were out here in the middle of the day in 90-degree heat and 90% humidity,” said Sam Roberts, a research associate at the University of Delaware. "We were in the mud; it’s saltwater, and all of our gear starts to rust because of the salt. Imagining a bird or anything being able to live out there and find strategies to survive is really incredible.”

Along with Greg Shriver, a professor of wildlife ecology, Roberts has been studying saltmarsh sparrows at Forsythe National Wildlife Refuge in Stafford Township, Ocean County, for five years.

At saltwater marshes, such as those at Forsythe, ocean water flows in and out with the tides, killing plants and animals that can’t handle the salt. Only a few kinds of grasses can grow here, and although there are plenty of insects, most larger animals cannot survive for long without fresh water.

Nonetheless, the saltmarsh sparrow has found a way. The birds “have evolved some adaptions for living in salty environments — they have [some of] the best kidney blood filtration system of any organism outside of marine mammals,” said Nate Rice, the associate curator of ornithology at the Academy of Natural Sciences of Drexel University, who was not involved in the University of Delaware study.

Despite their adaptations, saltmarsh sparrow numbers are rapidly dwindling across the Eastern Seaboard.

Roberts and Shriver have monitored hundreds of sparrow nests at the Forsythe refuge, trying to understand why the species is in trouble. As it turns out, we share many of the same problems.

“Climate change is definitely affecting this species," Roberts said. "The tidal [patterns] are changing. The tide is rising.”

As the planet continues to warm, sea levels are creeping higher and higher each year as polar ice melts into the ocean. And, according to researchers at Rutgers University, much of the land on the New Jersey coast is also sinking, making the total effect even worse — sea level is now approximately one foot higher than at the start of the 1900s.

This is a problem for saltmarsh sparrows, which nest in grasses on the ground.

“They time their nesting cycle with the monthly tides,” said Roberts. In the time between subsequent lunar high tides, saltmarsh sparrows can just barely lay, hatch, and raise offspring to the point that the baby birds can climb to safety — as long as nothing goes wrong, such as increasingly frequent floods, brought on just by high tides.

According to a report by the National Oceanic and Atmospheric Administration, by 2050, Atlantic City could expect 30 to 105 days of flooding from high tides. Storms, too, will become more common as the climate continues to warm, creating another source of unpredictable flooding.

» READ MORE: Climate change blamed for grim outlook on Jersey Shore flooding, federal report says

For baby saltmarsh sparrows, any extreme floods that occur outside of the expected monthly cycle due to lunar high tides can easily be fatal.

“You will see eggs underwater," said Roberts. The eggs can survive being submerged only for a brief time, and if the hatchlings are not old enough to climb to safety, they will drown.

What’s more, rising sea levels are gradually destroying what little habitat the sparrows have left, as coastal marshes are swallowed by the ocean on one side and confined on the other by development.

And a third threat is accelerating the sparrow’s decline: predators. At the Forsythe refuge, the scientists found that almost twice as many nests were eaten than succumbed to flooding.

“The [saltmarsh sparrows] that are breeding this year aren’t producing enough to replace the ones who die. [And] predation is a ‘double whammy’: if you aren’t getting [eaten], you’re going to get flooded," said Shriver.

The chief suspect: species that were introduced as people built up the Jersey Shore, such as rats. “With [development], you often see a lot more predators introduced to the area. That’s an important piece of the puzzle,” said Roberts.

If Roberts and Shriver can identify which animals are eating the nests, they can find ways to manage these predators, and prolong the bird’s survival beyond the current prediction of just 20 years. But they can do nothing about rising tides and frequent floods.

» READ MORE: The secret scourge of climate change? More raw sewage in Philadelphia’s waterways.

The researchers have called for the U.S. Fish and Wildlife Service to protect the saltmarsh sparrow and its habitat under the Endangered Species Act. The agency will not make a decision until 2023, but the Trump administration already has weakened the protections granted by the act. For now, Shriver asks for people to support the sparrow by talking with state representatives "about the importance of maintaining, restoring, and creating saltmarsh habitat.”

Preserving existing marshland and allowing birds to “migrate” inland with increases in sea level would ensure that the sparrow has a home, but would also benefit people living nearby. A report by the Nature Conservancy found that in Ocean County, coastal saltmarshes reduced property damage from flooding by 20%.

Roberts hopes that coastal residents will be moved to action by the plight of their winged neighbors. “We take for granted the existence, the presence, and persistence of species around us," he said. “... We hear in the news that species have gone extinct. But they are usually not in the view of our [homes].”

This story is part of Covering Climate Now, a global collaboration of more than 220 news outlets to strengthen coverage of the climate story.