Modeling Spatial Habitat Quality for the Cape Sable Seaside Sparrow

The Science Issue and Relevance: The Cape Sable Seaside Sparrow (hereafter sparrow) is endemic to South Florida and a key indicator species of marl prairie, the most diverse freshwater community in the Florida Everglades. Habitat loss and hydrologic alteration have precipitated the dramatic decline in sparrow numbers since 1992. Currently, the sparrow is restricted to the freshwater prairies of Everglades National Park and Big Cypress National Preserve. The Endangered Species Act protects the sparrow, and federal agencies have a statutory obligation to not jeopardize the survival of the species or adversely modify its critical habitat. The sparrow’s small population size and restricted range result in uncertainty about how to increase suitable habitat. Identifying factors affecting sparrow habitat suitability is essential if we are to expand the total area of suitable habitat over a gradient of environmental conditions. Our objective is to identify the characteristics of suitable sparrow habitat based on the relationship between daily sparrow distributions from 1992 to present and hydrologic and habitat variables.

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Methodology for Addressing the Issue: To meet our objective, we will develop species distribution models that incorporate hydrologic and habitat variables known to influence sparrow occurrence. Suitable habitat for sparrow feeding, mating, and nesting is characterized by distinct hydropatterns that support a mixed marl prairie. This prairie is comprised of a diverse community of grasses dominated by muhly grass. Periodic fires prevent invasion from hardwood species and taller, denser grasses, as well as the accumulation of dead plant material, all of which are unsuitable for sparrow nesting. After initial model development, we will link model outputs to demographic response. Coordination with the Ecostudies Institute and Everglades National Park staff will provide data necessary to relate occurrence models to reproductive metrics in order to determine habitat quality.

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Future Steps: Software using the models will be developed through an existing Joint Ecosystem Modeling (JEM) agreement. This agreement increases the accessibility of real-time and projected habitat suitability to inform water management decisions for the sparrow. The resultant software will provide state and federal agencies a useful tool to increase suitable habitat around existing sparrow populations by altering factors such as hydropatterns or frequencies of prescribed burns.