Date of Award
Master of Science
The once vast grasslands of the Northern Tallgrass Prairie region have undergone substantial modification since European settlement. Concomitantly, grassland birds have experienced drastic population declines. Since 1996, the United States Department of Agriculture (USDA) has actively promoted conservation buffers through its Continuous Enrollment Conservation Reserve Program (CCRP). A particularly popular buffer practice in the Midwest, filter strips are 6-36 m wide strips of herbaceous vegetation established along waterways to reduce soil erosion and improve water quality. Created in 1997, the Conservation Reserve Enhancement Program (CREP) provides opportunities to widen filter strips and diversify seeding mixtures. Understanding how filter strip design influences bird use of these habitats can provide conservation partners with information on how to better accommodate grassland bird species of concern into management objectives. During 2003 and 2004, 1 sampled 39 filter strips in southwestern Minnesota in order to assess the local- and landscape-level characteristics influencing bird use of USDA filter strips. I also investigated the local-level characteristics influencing arthropod occurrences in filter strips; emphasis was placed on taxa important to breeding bird diets. Arthropod richness, abundance, and drymass were negatively correlated with standing dead vegetation. Filter strip width, vegetation vertical density, and forb cover were not as important in my arthropod models as I had predicted. A nested analysis of local habitat variables showed that filter strip width, standing dead vegetation, forb cover, and vegetation vertical density were important in explaining variation in bird abundance and species richness, but adding arthropod drymass variables improved most models. Separate landscape models showed that bird occurrences were positively associated with herbaceous cover but negatively associated with developed areas and the density of herbaceous habitat edges in the 1 km radius surrounding filter strips. Logistic-exposure models showed that daily survival rates of songbird nests were negatively affected by filter strip width and standing dead vegetation. Adding arthropod information did not improve nest models. Predation was the major cause of nest failure for all nesting species. Though the primary purpose of filter strips will remain soil conservation, several opportunities exist for incorporating grassland bird conservation objectives into filter strip design.
Nicole Marie Davros
Davros, Nicole Marie, "Grassland bird and arthropod responses to USDA filter strip characteristics in southwestern Minnesota" (2005). Retrospective Theses and Dissertations. 18930.