Density and reproductive success of Florida grasshopper sparrows following fire

Abstract

Information on the response of the endangered Florida grasshopper sparrow (Ammodramus savannarum floridanus Mearns) to range management, especially prescribed fire, is needed to determine conservation strategies. Intensive management of grasslands for cattle grazing and conversion of grassland to other agricultural use is considered the greatest threat to the sparrow. Territory spot-mapping and estimates of reproductive success were examined in relation to time post-burn in managed cattle pastures at Avon Park Air Force Range, Highlands County, Florida from 1997-1999. We tested the hypothesis that sparrow density and reproductive success did not depend on time following fire. Contrary to previous work, there was no evidence that Florida grasshopper sparrow territory density depended on years post-burn (P = 0.842). The probability of reproductive success was significantly higher 0.5 year post-burn than at 1.5 years post-burn (P < 0.05) and 2.5 years post-burn (P < 0.01). No other significant differences were observed among years post-burn (P > 0.27 for each pairwise comparison between years). No simple trend or highly significant polynomial relationship between reproductive success and territory density was indicated (P > 0.41). Compared to other subspecies, Florida grasshopper sparrows exhibited relatively low density (0.22 territories/ha or less) and reproductive success (20%). Our results suggest increased reproductive success at a population level 0.5 year following fire, and did not suggest an association between territory density and individual reproductive success. Additional information is needed on the effects of seasonality of fire on Florida grasshopper sparrows.