Saltmarsh sparrows are the only species of breeding bird found nowhere else but the East Coast of the United States, where they live exclusively in coastal marshes, including several sites in Rhode Island. But the birds are predicted to go extinct within the next 50 years.
That’s the unfortunate news reported by University of Connecticut researchers Chris Elphick and Chris Fields earlier this month. Their data shows that the sparrows, which Elphick describes as small songbirds similar to the sparrows that visit many bird feeders in winter, have been declining at a rate of about 9 percent per year since the late 1990s.
|Saltmarsh sparrow by R. Crossley/Vireo|
“To put it in context, if your stock portfolio was declining at that rate, you’d be losing money fast. It’s pretty bad,” he said. “About three-quarters of the population has disappeared.”
According to Rachel Farrell, a member of the Rhode Island Avian Records Committee, birdwatchers in the Ocean State have made similar observations about saltmarsh sparrows, which they used to be able to find in good numbers at numerous salt marshes in the state. Now they report that the birds are few and far between. She said that birders have reported that the sparrows have all but disappeared from salt marshes in Little Compton, and they have declined somewhat in recent years at the marshes at the Charlestown and Quonochontaug breachways and around Ninigret Pond.
Walter Berry, a research biologist at the U.S. Environmental Protection Agency in Narragansett, has conducted annual surveys of saltmarsh sparrows at Ninigret and Quonochontaug since 2007, and while he hasn’t observed a population decline during that period, he is pessimistic about their future.
“Saltmarsh sparrows look like they’re holding their own at those sites, but judging by the quality of the habitat there, they won’t be holding their own for very long,” he said.
The cause of the range-wide decline of saltmarsh sparrows is uncertain, though sea level rise and tidal restrictions at marshes are major factors.
“The presence of a road across a marsh that restricts the natural tidal flow, even if there’s a culvert that allows the water to go in and out, is one of the most important predictors of decline,” Elphick said. “We found no decline in marshes without tidal restrictions, but the trouble is that nearly all marshes have some sort of tidal restriction.”
He notes that locations that are experiencing the greatest sea level rise are also the sites where the decline in saltmarsh sparrows is greatest. That’s because the birds nest on the ground in the marsh, and the high spring tide causes many nests to flood.
“If that only happened once a month, it wouldn’t be a problem because the birds’ nesting cycle takes 23 or 24 days to complete,” Elphick explained. “So if there’s a 24-day window between spring tides, they can reproduce. But if that window gets shorter because of big storms or onshore winds driving the water high up into the marsh, or if the marshes don’t drain the way they would naturally, suddenly the birds don’t have enough time to reproduce.”
To complicate things, Elphick said that as sea level is causing the peak of the high tides to get higher.
“It doesn’t take too much sea level rise to flip the switch for the birds,” he said. “Literally, a couple inches can make the difference.”
To draw their conclusions, Elphick, Fields and their colleagues surveyed for salmarsh sparrows at 1,800 locations throughout the birds’ breeding range and compared their results to similar surveys conducted in the 1990s and 2000s. They also monitored nesting success and estimated the survival rates of adult birds.
Sadly, the researchers say there is little that can be done to protect the birds in the long term, since any steps taken now to reduce sea level rise won’t have a practical effect until it’s too late. They are exploring several short-term or temporary fixes, however, like identifying the marshes that are least susceptible to the effects of sea level rise so they can be protected from development or alteration. They are also identifying locations where it is possible for the marshes to move inland as sea level rises so those inland locations can be protected as well.
But ultimately, Elphick is not optimistic about the future for saltmarsh sparrows.
“This is a really difficult problem, one we’ve ignored, and the longer we ignore things the harder they are to fix,” he said. “It’s not just about the sparrows, though. That’s just one species in these marshes. If we start acting now, all the things we do to benefit this sparrow will also benefit all the other species in the marsh, even if it doesn’t work for saltmarsh sparrows.
“This sparrow tells us there’s something bad happening in the system that we have to act on now if we’re not going to run into bigger problems down the road,” he added.
This article first appeared in EcoRI.org on July 20, 2016.