The Effect of Habitat Type and Prescribed Fire on the Abundance of Arthropod Prey for the Endangered Florida Grasshopper Sparrow (Ammodramus savannarum floridanus)

Abstract

The introduction of nonnative grazers and plants, as well as alterations to native fire regimes in grassland systems, can directly and indirectly affect the abundance of arthropods. In this study, we used sweep-net sampling at two sites occupied by the critically endangered Florida grasshopper sparrow (Ammodramus savannarum floridanus Mearns) in Osceola County, Florida, to assess how the abundance of all arthropods (orders pooled) and the four most common arthropod orders varied between native dry prairie and semi-improved cattle pasture habitat (2015–2016). We also examined the role of time since fire and fire season on arthropod abundance in both habitat types. The abundance of all arthropods, Hemiptera, Orthoptera, and Coleoptera was higher in pasture than dry prairie, but the mean body length of Orthoptera was smaller in pasture. Fire year and fire season did not affect arthropod abundance when data from both sites were combined. However, when examined separately, Orthoptera at the dry prairie site were more abundant in habitat burned in the current year than previous years, supporting the hypothesis that Florida grasshopper sparrows preferentially select recently burned prairies because they support greater resource availability. Orthoptera at the pasture site showed no significant response to fire year or season. This study is important because it is the first to compare arthropod prey abundance for Florida grasshopper sparrows across dry prairie and pasture habitat and has important implications for prescribed fire management.