Wrens and sparrows flitter around the salt marshes of northeast Florida, clutching onto individual blades of grass with their tiny feet. They seek shelter in the dense cordgrass (Spartina alterniflora) covering the shorelines of the Nassau River and nearby tidal rivers of northeast Florida. Salt marshes occur between high and low tidelines, provide habitat for numerous animals, and act as coastal filters as they absorb pollutants and help keep sediment from washing out to sea. Two of the avian subspecies that rely on salt marshes for survival are the Worthington’s marsh wren (Cistothorus palustris griseus) and MacGillivray’s seaside sparrow (Ammodramus maritimus macgillivraii).
During a Biological Status Review conducted by FWC in 2010-2011, the Worthington’s marsh wren met the criteria to be listed as a Threatened species in the state of Florida; and the MacGillivray’s seaside sparrow is under consideration for federal listing by the U.S. Fish and Wildlife Service. Currently, little is known about these two subspecies, so FWRI researchers are studying their abundance, nest survival and post-fledging survival in association with their habitat.
This four-year study is critical for the development of management actions to achieve population stability. Historically, the range for these wrens and sparrows encompassed the salt marshes in Nassau, Duval, St. John’s, Flagler, and Volusia counties. Comparisons between surveys conducted in 1975-1976, 1987-1988, and 2000-2001 indicated that the wrens and sparrows have undergone at least a 40 percent range contraction and a decrease in population size within Florida. During the first two years of this study, researchers found that no wrens or sparrows nested south of the St. John’s River, indicating that the previously documented range contraction remains unchanged. There is no evidence of recovery to historically occupied areas.
This research will provide important data on the habitat needs, baseline population distribution and abundance of these small birds. Land managers can use the results to determine what types of habitat need to be restored or maintained to sustain the marsh wren and seaside sparrow populations in northeast Florida.
- Objective: Estimate the percent likelihood of wren and sparrow breeding season occupancy based on habitat variables and landscape components.
- Objective: Estimate abundance of wrens and sparrows (number of breeding individuals) along the northeast coast of Florida to provide baseline information to determine population size and trend.
- Objective: Identify habitat features associated with nest-site selection by nesting wrens and sparrows.
- Objective: Estimate nest survival as a function of habitat features at multiple spatial scales.
- Objective: Identify habitat use and resource selection of fledgling wrens.
- Objective: Estimate post-fledging survival of the wrens as a function of habitat features at multiple spatial scales. (5 & 6 wren specific)
- Objective: Synthesize results from survey and survival studies and make management recommendations about habitat features required to support high densities and productivity of wrens.