A search for Chesapeake’s vanishing saltmarsh sparrow


It seemed like an inauspicious start to a morning of birding.

Ever so slowly, Pete McGowan guided a small powerboat into the marsh at the mouth of the Transquaking River on Maryland’s Eastern Shore. McGowan, a biologist with the U.S. Fish and Wildlife Service, threaded the vessel through a grassy maze of increasingly narrow channels. Finally, he ran out of water, blocked by a towering green wall of phragmites.

With that, Kevin Reifenberg and Olivia Tran — a pair of “on-call biologists,” as they described themselves — slipped over the side and plunged into the thicket of 7-foot high reeds. They quickly vanished from sight, their slog through the morass evident only from the sound of thrashing, splashing and their increasingly faint voices.

The trio was one of 15 crews searching in marshes from Virginia to Maine this summer for the rare, vanishing saltmarsh sparrow, a secretive little brown and gray bird with orange around its cheeks and a whitish belly. They nest only in grassy tidal marshes along the northeastern Atlantic Coast.

And they’re in big trouble. Rising sea level is inexorably drowning their nests and nestlings.

“It’s in pretty dire straits, to be honest,” said Rebecca Longenecker, another USFWS biologist working on the survey. “We know that over 80% of the population has disappeared since 1998. Four of every five saltmarsh sparrows are gone. So it’s pretty striking, pretty alarming stuff.”

The birds were living dangerously even before climate change began to hit them. Saltmarsh sparrows build their nests beneath the grass in “high marsh,” the most elevated parts of the squishy interface between land and water. High marsh typically floods only once or twice a month — on spring tides, when the sun, Earth and moon align to pull the water higher — or during coastal storms.

By nesting in such a precarious setting, the birds have evolved a reproductive cycle that just fits into the lunar timetable. They can lay eggs, hatch them and nurture the chicks within about 28 days, between the extra-high tides.

But high marsh is increasingly turning into waterlogged low marsh. Sea level is rising faster than marshland can build itself up with accumulating sediment and decomposing plants. Along the Delmarva Peninsula, the water is rising even faster because the land, itself, is ever so slowly sinking — a geologic aftereffect of the end of the ice age 10,000 years ago.

Those rising waters, coupled with historic human alteration of marsh and nest predation by other animals, have put saltmarsh sparrows in a tailspin, biologists say. A survey conducted a decade ago found that the birds’ population had plummeted 87% since 1998.

Surveys amid silence

This year, federal and state wildlife agencies, in partnership with universities and nonprofit conservation groups, launched a survey to check up on the saltmarsh sparrow population. They also checked for some other marsh-dwelling birds, such as the black rail and seaside sparrow — which are also at risk from the loss and degradation of salt marsh habitat.

As best they could, survey crews revisited 1,700 locations from Maine to Virginia that had been surveyed a decade ago, so they could track any differences in habitat and bird abundance over that time. One spot that was checked along Maryland’s coastal bays in the 2011–12 survey proved impossible to reach, Longenecker recalled, because it is now about 70 yards out in the water.

Hitting each assigned spot twice for consistency, Reifenberg and Tran helped to canvass an important portion of the sparrow’s range. Delaware, Maryland and Virginia accounted for more than a third of the bird’s population in the last survey.

McGowan, the boat’s skipper, is a longtime staffer in the USFWS Chesapeake Bay field office. Reifenberg and Tran are members of the service’s “rapid response team,” recruited from elsewhere to help with the survey. Reifenberg is almost local, from Spotsylvania County, VA. But Tran hails from South Florida. She said she enjoyed spending time in the “Everglades of the North” — the Chesapeake Bay, with its “cute” birds like the saltmarsh sparrow.

On the Transquaking, Reifenberg used a handheld GPS to find the right spot in the phragmites jungle. The reeds were so tall and thick that he and Tran could only see a patch of sky overhead. Instead of pulling out binoculars, they unpacked a waterproof portable speaker. After listening intently for five minutes, they began to play a series of pre-recorded bird calls, with short gaps in between. Clipboards in hand, they cocked heads to listen for any calls back from the wild.

In that 12-minute span, they heard the grunting call of a Virginia rail, a chickenlike bird that’s not in the same trouble because of its much broader range.

Virginia rails are “pretty cryptic,” Reifenberg explained. “They’re really small and just run around in the marsh. You rarely see them, but you do hear them. They’re super-boisterous.”

But at that first stop, Reifenberg and Tran didn’t hear any soft chips or high-pitched notes of saltmarsh sparrows. That was almost to be expected: Saltmarsh sparrows prefer to nest in shorter, wispier grasses. Phragmites, an invasive non-native wetland plant, grows too densely and tall.

The next sites on their day’s survey sheet took them into Fishing Bay, where they found better habitat — vast marshy meadows of light, wavy cordgrass and saltgrass. Reifenberg kept an eye and ear out for birds while Tran took inventory of the marsh vegetation before joining in the search. They scanned the marsh with binoculars and strained to hear the calls of their target species amid a cacophony of tweets, chirps, trills and twitters carried on a breeze from the orchestra of the more common birds flitting about the marsh.

Finally, the payoff. “All right, got one,” Reifenberg whispered, pointing to where he saw a saltmarsh sparrow poke up from some distant grass before disappearing a moment later. Spotting one is like playing the arcade game whack-a-mole, he said. They’re tough to identify on sight with confidence because they appear so fleetingly.

When the survey is completed next year, it could provide a fresh warning about the fate of the saltmarsh sparrow population. Experts have estimated it’s declining 9% a year. If that’s so and it continues, Longenecker said, “we could see a pretty substantial population collapse within 50 years.”

A rescue plan

Biologists hope the survey results can guide (and possibly goad) them as they attempt to rescue the birds from oblivion. Slashing emissions of climate-warming greenhouse gases would slow the rise in sea level and give tidal marshes more time to migrate inland or raise elevation.

But that’s far from certain and could take decades. So, a conservation plan has been developed by the Atlantic Coast Joint Venture, a partnership of state and federal wildlife agencies and conservation groups working to save this and other native bird populations on the Atlantic Flyway.

The plan lays out a menu of stopgap measures, some relatively untried, to restore some of the marsh habitat that’s been lost and to give the birds more room to nest. One potentially fruitful effort would be to try to undo or remedy the widespread ditching of the marshes that took place decades ago, either for farmland drainage or to control mosquitoes. The ditches have trapped water in the marsh and prevented it from building itself up with new deposits of sediment. The resulting marshscape looks like a waffle pockmarked with pools of water — unsuitable now for ground-nesting birds.

The plan proposes “runneling” or digging little shallow ditches to drain those pools. Another option, tested so far in a couple New England states, involves cutting marsh hay and rolling it into the ditches, where it can trap sediment and over a period of years naturally fill in the open water. Yet another, quicker but more expensive and logistically complicated, approach that has already been tried at Blackwater National Wildlife Refuge involves pumping a thin layer of river sediment onto a low marsh to raise its elevation.

Promising as any those might be, experts say it’s not clear how much can be done, or how quickly, or what the costs would be.

“No doubt it is a formidable challenge,” said Aimee Weldon, a USFWS biologist who helped write the plan. “We’re trying to react to sea level rise and other impacts on a very shortened time scale, trying to learn as we go as quickly as we can. Our focus right now is getting as much habitat on the ground as we can.”

The plan acknowledges that the saltmarsh sparrow numbers are likely to keep falling over the next decade, and by 2030 could drop to a critical threshold of 10,000 birds. But the plan aims by then to have 23,000 acres of high-quality breeding habitat to halt the slide and then slowly rebuild the population to around 25,000 by 2069. To do that, they estimate they’ll need more than three times as much marsh habitat — 80,000 acres.

“It can be a pretty dire feeling,” Weldon acknowledged, “but we still believe that there’s hope — if not for the saltmarsh sparrow then for the other birds that aren’t quite as affected. … We are hoping to rapidly learn about the restoration techniques that work and then scale up.”

Meanwhile, at the end of their morning in and around Fishing Bay, Reifenberg and Tran had tallied sights or sounds of three swamp sparrows, seven seaside sparrows (including one that flew closer to check out the recorded come-ons), two Virginia rails (one of which also ventured closer), nine marsh wrens and several other birds.

Plus, they had confirmed two saltmarsh sparrows. That seemed encouraging. But then again, Fishing Bay is the bird’s stronghold in the Chesapeake, according to earlier survey data.

“You sample eight points a day for five days, and you see maybe one saltmarsh sparrow,” Reifenberg said. “And some days, you don’t see any at all.”

bayjournal.com, 8 September 2021
; https://www.bayjournal.com