The saltmarsh sparrow (“a secretive bird with skulking habits and a barely audible song,” according to the Cornell Lab of Ornithology) makes its home in salt marshes along North America’s Atlantic and Gulf coasts. It’s listed as “vulnerable” on the IUCN list of threatened species, which is not as bad as “endangered,” “critically endangered,” or “extinct in the wild,” but somewhat worse than “least concern,” and “near threatened.”
In other words, conservation-minded scientists and wildlife managers should be interested in mitigating the threats the bird faces in the wild, which revolve around habitat loss.
Salt marshes are complex ecosystems regularly inundated by tides in which tiny variations in elevation – sometimes just a few centimeters – can mean the difference between daily or twice-per-month flooding. As a result, completely different plant communities develop in low marsh and high marsh areas. Saltmarsh sparrows tend to build their nests in the high marsh areas, among plants that grow only at higher elevations.
Humans have not always recognized the important services salt marshes provide (they help prevent coastal erosion, for example, and also provide food and shelter for fish and other aquatic species), and development, including water-control efforts and in-fill projects, have destroyed or degraded a lot of the salt marsh habitat that once lined much of the U.S. coast. Invasive species, particularly Phragmites australis, or common reed, and rising sea levels further threaten the marshes and saltmarsh sparrows that are left.
Salt marsh restoration projects typically involve elements designed to reestablish natural conditions, like removing or altering barriers to tidal flows or eliminating Phragmites stands. But, as a team of scientists from the University of Connecticut recently reported in the journal Restoration Ecology, even when managers are able to successfully alter a salt marsh plant community through restoration, that may not translate into increased habitat for saltmarsh sparrows.
The researchers, working in 18 different Connecticut marshes, compared remnant plots of healthy marsh to plots that had been restored, either through direct removal of Phragmites or renewed tidal flow. They found that tidal flow restoration appeared to control Phragmites growth and allow for the reestablishment of native low marsh plant communities, but not the plants typical of high marsh areas, where saltmarsh sparrows like to build their nests; consequently, there were fewer saltmarsh sparrows, and fewer nests, in the tidal flow restoration plots compared to the remnant marsh plots.
“[D]espite its successes,” the authors write, “saltmarsh tidal restoration is not providing conservation value for some of the most vulnerable species that use tidal marshes.” They go on to suggest that an emphasis on restoring high marsh areas, in addition to low marsh areas, is necessary to help species like the saltmarsh sparrow.
The saltmarsh sparrow may be a secretive, skulking bird, but it’s a fundamental part of salt marsh ecosystems. In order to fully rebuild salt marshes, future restoration efforts will have to target all elevations, even if they’re only a few centimeters apart.