by Marisa Baldine
March 01, 2021
Saltmarsh sparrows are small, inconspicuous birds with a quiet song. Birders sometimes catch fleeting glimpses of them gripping stems over the grass line, studying the marsh below for bugs and seeds to feed on. Although not always seen, this bird lives exclusively in tidal salt marshes found on the east coast of the United States, many of which are in the Chesapeake Bay.
Tragically, the saltmarsh sparrow population is in steep decline due to severe disruption to its salt marsh habitat. It is estimated that since 1998, the population of the saltmarsh sparrow has dropped by 87% —meaning that more than four out of every five sparrows are lost. Their population is projected to drop at a rate of nine percent, leading to extinction within the next 30 years.
Rising sea levels and changing weather patterns caused by climate change are effectively drowning tidal marshes where saltmarsh sparrows live and raise their young. For generations, these birds have maintained a careful balance for nest placement: high enough to avoid the flood line, low enough to avoid predators, late enough in spring to have warm weather and early enough to avoid summer storms. But climate change has thrown all of this evolutionary conditioning to the wind. The floods that the saltmarsh sparrows have avoided for so long are becoming less predictable and more severe, and each year more chicks are drowning.
“The environment is always changing and birds, in a sense, are always evolving through natural selection in response to changes that usually go back and forth, but this is a big one-directional change that is happening too fast for the sparrows to evolve and respond to,” said David Curson, the Maryland director of bird conservation for the Audubon Society.
A little flooding can be managed and has always been part of the sparrow's life. In the past, sparrows were able to keep their nests out of reach from the daily high tides by coordinating their nesting cycle with the monthly high tide lunar cycle. The cordgrass that nests are built under form a protective arch that typically keeps eggs from floating away, even when flooding occurs. However, severe storms and rising sea levels cause flooding mid-cycle that the birds can’t plan around, and the flooding is too significant for even the high-arched nesting areas. When you’re only a couple of inches tall and unable to fly, a few inches of rain can be catastrophic. An entire breeding season can be wiped out with one or two storms.
Referencing a 2011 salt marsh nesting survey led by the Audubon Society, Curson said, “There are places where we found saltmarsh sparrows in 2011 and 2012 where we don’t see them anymore, so we’re really seeing the impact of this change. To most birdwatchers, all of this is happening in places that are inaccessible to them so they’re not noticing it because you don’t often go to places where you will see saltmarsh sparrows.”
In addition to having their nests flooded, saltmarsh sparrows are also dealing with the loss of salt marsh habitat all together. Traditionally, salt marshes and wetlands have been abundant in the watershed, specifically on Maryland’s tidal shores.
According to Curson, “The regional analysis of [the 2011 and 2012 survey] data showed that a quarter of the world’s population of the saltmarsh sparrow breeds in Maryland. Which means we have a big responsibility for them here in the Chesapeake Bay and also in the coastal bays.”
But salt marshes aren’t only worth saving for the habitat they provide birds. They have many other environmental benefits. Marshes trap polluted runoff, keeping sediment and other pollution out of the Bay, which keeps aquatic life healthy. During severe storms, the marshes serve as a buffer and protect nearby communities from flooding. And a wide variety of species are supported by the marshes which boosts the ecotourism industry throughout the region.
The Chesapeake Bay Program established a target in the most recent Watershed Agreement of creating or reestablishing 85,000 acres of tidal and non-tidal wetlands and enhancing function of an additional 150,000 acres of degraded wetlands by 2025. Salt marshes, which are brackish or saltwater wetlands, are included in this effort.
A number of Bay Program partners including the Audubon Society, United States Fish and Wildlife Service, the Chesapeake Bay Foundation, Maryland Department of Natural Resources and others are working extensively to conserve existing marshes in areas such as Blackwater National Wildlife Refuge, Deal Island Wildlife Management, Barren Island and James Island. By using the nesting data from the Audubon Society’s 2011 survey, conservationists can target the most critically important nesting areas.
The saltmarsh sparrow is the canary in the coal mine of wetland climate change, if we don’t listen to this warning, we risk losing some of our most valuable natural resources of the Chesapeake region. But according to Curson, there is hope for saltmarsh sparrows if we can prioritize marsh conservation.
“If we can double-up our goals and make sure we have nesting sites in places the sparrows use and need with the right kind of salt marsh, then that will save the sparrow.”