Effects of Grazing Intensity and Temporal Application of Grazing Treatments on Nongame Birds in North Dakota Mixed-Grass Prairie

Grazing occurred naturally in the northern Great Plains and influenced many natural processes in grassland ecosystems, including the habitat selection of breeding birds. Grazing, mainly for livestock production, is still an important land use practice and is one that impacts millions of hectares on both public and private land in the United States. In North Dakota alone, various grazing practices affect over 4 million hectares (10 million acres), making it one of the most important land uses, second only to cereal and oil crop production. To better understand how grazing affects nongame breeding birds, a study was conducted at Central Grasslands Research Extension Center (CGREC) to determine the effects of four levels of grazing intensity on nongame bird populations and grassland habitat. In addition, two earlier studies, conducted at CGREC were repeated, one in native prairie and the other in Conservation Reserve Program (CRP) grasslands, to determine the temporal effects of grazing systems on nongame bird populations and habitat. In addition, two earlier studies, conducted at CGREC were repeated, one in native prairie and the other in Conservation Reserve Program (CRP) grasslands, to determine the temporal effects of grazing systems on nongame bird populations and habitat. Bird surveys were conducted along permanent belt transects and during a 15 minute “walk-about” three times per year on treatment plots during the summers of 2001 and 2002. Vegetation structure was characterized from measurements taken parallel to the bird survey transects, two times per year for each treatment plot. Many species of nongame birds responded differently to the effects of grazing intensity and to the temporal effects of grazing systems in both native prairie and CRP grasslands. Overall breeding bird densities and vegetation structure were negatively affected by increasing levels of grazing intensity in mixed-grass prairie. Clay-colored sparrows, grasshopper sparrows, and savannah sparrows reached their highest densities in the light and moderate grazing intensity treatments whereas their lowest populations occurred in the high and extreme grazing intensity treatments. In contrast, densities of chestnut-collared longspurs, horned larks, and various species of shorebirds were highest in the high and extreme grazing treatment plots. Nongame bird densities and species richness during this study period were lower for all grazing treatments in native prairie and CRP grazing system grasslands when compared to earlier studies. Among grazing treatments, season-long pastures exhibited similar or slightly higher densities of nongame birds when compared to rotational grazing treatments in the native prairie and CRP study areas. However, rotational grazing treatments supported more species and are probably beneficial because they provide areas of undisturbed habitat during the breeding season. Results from this study suggest that management of grassland habitats can be manipulated to provide nesting habitat for certain species of grassland birds depending on particular management goals