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.
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| 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.
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