Characteristics of Florida Grasshopper Sparrow Habitat Across a Gradient of Population Abundance and Persistence at Avon Park Air Force Range

Population trends of Florida Grasshopper Sparrows ( Ammodramus savannarum floridanus ) at Avon Park Air Force Range (APAFR) have been monitored using standardized point counts since 1996. Data collected from 1996-2001 were used to examine the spatial distribution of Florida Grasshopper Sparrows during those years. That analysis identified areas consistently used by breeding sparrows and estimated probability contours identifying areas where 50%, 75%, and 95% of breeding sparrows were located. The population of Florida Grasshopper Sparrows at APAFR has declined drastically since 1996, and the extant sparrows are largely restricted to areas identified by the spatial analysis as containing 50% of the population. Those results suggest that the highest abundance and persistence of Florida Grasshopper Sparrows at APAFR occurs within the 50% probability contours. We measured vegetation structure across the three probability contours and a fourth zone where few to no sparrows were sighted to identify key characteristics of habitat associated with variation in abundance and persistence of Florida Grasshopper Sparrows at APAFR. Areas with the greatest probability of sparrow occurrence had greater cover of runways and tended to have more bare ground and runner oak than areas with lower probabilities of occurrence.