The area enrolled in the Conservation Reserve Program in the Great Plains is enormous: nearly 18 million acres, or more than 7 million hectares, in Montana, North Dakota, South Dakota, Wyoming, Nebraska, Colorado, Kansas, Oklahoma, and Texas. This change in land use has had a huge influence on grassland bird populations. Many, but certainly not all, grassland species flourish in CRP habitats. Responses to the program vary not only by species, but by region, year, vegetation composition in a field, and whether or not a field was hayed or grazed. Further, the large scale of CRP has allowed researchers to begin to address other important conservation questions, such as the effect of the size of habitat patch and the influences of landscape features. Although the CRP provisions of farm bills have been beneficial to grassland birds, it is critical that gains in grassland habitat induced by the program not be offset by losses due to sodbusting.