We developed a spatially explicit population-viability-analysis (PVA) model to evaluate different management options for the endangered Florida Grasshopper Sparrow (Ammodramus savannarum floridanus). We also conducted a sensitivity analysis to determine which parameters had the greatest effect on population viability. The model was most sensitive to environmental variation and least sensitive to carrying capacity, initial abundance, and level of correlation in demographic rates between subpopulations. The model that represented present conditions predicted a 22% chance that the population will fall below the extinction threshold of 60 male Florida Grasshopper Sparrows within 50 years. Reintroduction to large prairie sites and prairie restoration reduced the chance of falling below the extinction threshold and increased the number of subpopulations occupied. Loss of dry prairie located on private land adjacent to existing Florida Grasshopper Sparrow subpopulations increased the probability of falling below the extinction threshold to 66%. We caution that the strength of PVAs is not in predicting absolute values of viability or number of individuals but, rather, in evaluatuating the relative effects of different management options. We found that increasing the amount of prairie habitat, especially core habitat, had a strong positive effect on viability. If the Florida Grasshopper Sparrow reaches recovery goals developed by the U.S. Fish and Wildlife Service (10 subpopulations with ≥50 males per site), we estimate that the metapopulation has a 99% probability of remaining above the extinction threshold. Our analyses indicate that the Florida Grasshopper Sparrow is currently vulnerable to extinction, but various management practices can increase population viability.
Análisis de Viabilidad Poblacional de Ammodramus savannarum floridanus: Evaluación de Metas de