Prescribed fire influences occupancy and abundance of grassland-nesting passerines overwintering in pine forests of Central Louisiana

Abstract

We surveyed longleaf (Pinus palustris) and loblolly pine (P. taeda) stands burned within 0–7 years to examine the influence of prescribed fire on grassland-nesting passerines that overwinter in pine forests of central Louisiana, USA. We modeled occupancy and abundance of Bachman’s sparrows (Peucaea aestivalis), Henslow’s sparrows (Ammodramus henslowii), and sedge wrens (Cistothorus stellaris) in relation to stand type, years since burn, and site-scale vegetation conditions. We also used analysis of variance to compare vegetation conditions across study sites and detection points for these three species. Bachman’s sparrow occupancy was 3.7 times greater in longleaf stands compared to loblolly stands and decreased 30 % with every 10 % increase in canopy cover. We also found a positive relationship between Bachman’s sparrow density and the density of herbaceous plants in both stand types. Henslow’s sparrows used herbaceous vegetation within longleaf pine stands burned 0–2 years ago that was significantly taller than what we observed at the site scale, but the best fit models for Henslow’s sparrow occupancy (maximum vegetation height, bare ground, herbaceous cover) had overlapping confidence intervals. Henslow’s sparrow density was positively associated with bare ground and negatively associated with litter depth. Sedge wren occupancy decreased 50 % with every 10 % increase in canopy cover. Sedge wren density increased with increasing percent herbaceous cover, however, the 95 % confidence intervals for this relationship largely overlapped. Our study reiterated the importance of frequent (<3 years) prescribed fires to maintain habitat used by grassland-nesting passerines that overwinter in southeastern pine forests.