Breeding bird use of grasslands enrolled in the Conservation Reserve Program in the northern Great Plains

This dissertation examines bird use of grasslands enrolled in the Conservation Reserve Program (CRP) in four states in the northern Great Plains. Many methods are available to survey birds in grasslands, but there is no consensus as to which method is the most suitable. During two years (1995 and 2000), this study evaluated whether total-area count methodology was an effective alternative to point counts in estimating occurrence and abundance of breeding birds using CRP grasslands. Less effort was required using total-area counts than point counts. Seventeen of 26 bird species showed greater odds of detection using total-area counts than point counts; one species showed greater odds of detection using point counts. Density estimates for point counts were generally higher and more variable than density estimates for total-area counts.;Management disturbances of CRP grasslands generally are not allowed unless authorized to provide relief to livestock producers during drought and other natural disasters or to improve the quality of CRP vegetation. This study assessed the effects of haying on 20 bird species in CRP grasslands between 1993 and 2008. Breeding bird densities were compared in idled and hayed fields to evaluate changes 1-4 years after haying. Haying had either positive or negative effects on birds, depending on the species, county, and number of years after the disturbance. The responses of some species changed direction as the fields recovered from haying. This study provides important information on the strength and direction of changes in bird populations following haying.;The Brown-headed Cowbird is an obligate brood parasite. Cowbirds reach their highest abundance in the northern Great Plains. This study examines cowbird brood parasitism and densities in the northern Great Plains between 1990 and 2006. The overall rate of parasitism in 1902 passerine nests was moderate but the rate of multiple parasitism among parasitized nests was heavy. Nests found in CRP grasslands within areas of higher female cowbird abundance had higher rates of cowbird parasitism than those in areas of lower cowbird abundance. Densities of female cowbirds were positively related to densities and richness of other birds in the community.