Reclaimed Coal Mine Grasslands and Their Significance for Henslow's Sparrows in the American Midwest

Abstract

Abstract Present methods of surface coal-mine reclamation in the Midwest produce large grasslands, some of which exceed 2,000 ha in extent. Total “mine grassland” production in southwestern Indiana alone is well in excess of 70 square miles (180 km2). Our work in 19 reclaimed coal mines in southwestern Indiana indicates that mine grasslands harbor many Henslow's Sparrows (Ammodramus henslowii). We base that conclusion on point-count and line-transect surveys that yielded between 200–300 singing male Henslow's Sparrows during the 1997 and 1998 breeding seasons. Those survey results imply an uncorrected population density of ∼0.10 males per hectare, and a corrected density of ∼0.16 males per hectare (correcting for undetected males). Extrapolating this corrected density to total habitat coverage suggests an overall population of a few thousand Henslow's Sparrows in the mine grasslands of southwestern Indiana. Small-scale vegetational surveys suggest that much of the within-mine variation in Henslow's Sparrow abundance reflects local vegetative structure, with males preferring sites typically associated with that species of bird: tall, dense grass-dominated vegetation with a substantial litter layer. Management for this kind of vegetative structure could greatly increase the number of Henslow's Sparrows inhabiting reclaimed mines. Midwestern mine grasslands could play a significant role in stabilizing the populations of Henslow's Sparrows and other grassland birds.