ANNUAL SURVIVAL OF AN ENDANGERED PASSERINE, THE FLORIDA GRASSHOPPER SPARROW

We sought to determine annual survivorship for adult male and juvenile Florida Grasshopper Sparrows (Ammodramus savannarum floridanus), a federally endangered taxon whose range is limited to central Florida. We captured, banded, and resighted 161 birds at two study sites, Avon Park Air Force Range and Three Lakes Wildlife Management Area, from 1995–1998. For the period 1995–1998, we estimated mean adult annual male survivorship with program JOLLY to be 48.2% and 53.3% at these two sites. Because sample size of banded juveniles was small, we were unable to use the JOLLY program for this age group. Therefore, we developed a new method to determine juvenile survival that incorporated known adult annual survivorship, reproductive success, and territory densities. We estimated juvenile survivorship to be 35.1%, which was 66–73% of annual adult survivorship. This survival rate was greater than the generally assumed but undocumented 25–50% survivorship rate suggested in the literature.