Impacts of Agricultural Tillage on Grassland Birds in Western South Dakota

Xeric, mixed-grass landscapes are changing rapidly as native grasslands are converted to cropland. We surveyed birds to compare their use of grassland and cropland habitats and to evaluate whether their abundances were related to grassland fragment size. Surveys were conducted in western South Dakota at 146 sites that were stratified by habitat type, landscape composition and fragment size. The abundances of 13 of 14 species were 1.2–140 times higher in grasslands than in cropland. Greater prairie-chicken, sharp-tailed grouse, burrowing owl, Baird’s sparrow, northern harrier, and short-eared owl never occurred in cropland. Abundances of grasshopper sparrow, western meadowlark and chestnut-collared longspur were higher in grassland than in any other habitat type. A positive relationship between grassland fragment size and grasshopper sparrow abundance indicates that it may not be enough to conserve small parcels of habitat even for the most common grassland species. The future of grassland bird populations will depend on grassland habitat conservation practices because most species are grassland specialists.