Henslow’s Sparrow shows positive response to prescribed fire rotation

Abstract

We examined Henslow’s Sparrow (Centronyx henslowii) response to prescribed fire at 32 grasslands at Big Oaks National Wildlife Refuge in southeastern Indiana from 1999 to 2009. We burned grasslands in the spring between 1999 and 2007 and monitored Henslow’s Sparrows for up to 4 yr after treatment. We used linear mixed models to analyze our data. Henslow’s Sparrow counts were correlated with time since prescribed fire and grassland size. The estimated changes in mean Henslow’s Sparrow density relative to pre-burn densities were −0.19, 1.15, 0.74, and −0.68 birds ha−1 for 1–4 breeding seasons after a spring burn, respectively. We found that Henslow’s Sparrows preferred larger grasslands both during the first breeding season after prescribed fire, when vegetation was presumed to possess less litter and structural density, and during the fourth breeding season after fire, when vegetation was presumed to be a more ideal composition, but preferred smaller grasslands in the interim. Thus, grassland size shapes the magnitude of Henslow’s Sparrow population response to fire, with populations in smaller grasslands experiencing greater amplitude changes. Larger grasslands might provide more habitat diversity following prescribed fire, attenuating population change. On average, Henslow’s Sparrows responded positively to prescribed fire in a network of grasslands and cumulative net change in densities were highest three breeding seasons after a burn suggesting that maintaining this burn frequency would be beneficial to Henslow’s Sparrow abundance.