The largest number of grassland species are found in the northern Great Plains, especially in the Dakotas, Montana, and adjacent Canadian provinces. The fewest species are found from the Rocky Mountains westward and in most of eastern North America.
Grassland birds show the most consistent declines of any group of birds monitored by the BBS. Fewer than 30 % of the species show increasing populations. Declines prevail throughout North America. Areas with increasing trends are generally small and localized.
Most grassland birds have been constantly declining since the BBS was initiated in 1966, and were probably declining during the decades preceding the BBS. Factors responsible for this decline include the destruction of suitable habitats as well as increased mowing of remaining grasslands for hay production. Since the mid- 1980s, the Conservation Reserve Program (CRP) has been responsible for the creation of millions of acres of grasslands across the United States. Some grassland birds have benefitted from the habitats created by the CRP (Johnson and Schwartz 1993, Reynolds et al. 1994), reducing the rates of decline or even reversing the declining trends for some species. Despite these short-term benefits from the CRP, the long-term prospects for most grassland birds remain bleak.
Johnson, D.H., and M.D. Schwartz. 1993. The Conservation Reserve
Program and grassland birds. Conserv. Biol. 7:934-937.
Reynolds, R.E., T.L. Shaffer, J.R. Sauer, and B.G. Peterjohn.
1994. Conservation Reserve Program: benefit for grassland
birds in the Northern Plains. Trans. No. Am. Wildl. &
Natur. Resour. Conf. 59: 328-336.