Effects of Intercropping Switchgrass in Loblolly Pine Plantations on Bird Communities

Intercropping switchgrass (Panicum virgatum) between tree rows within young pine (Pinus spp.) plantations is a novel method to generate lignocellulosic biofuel feedstocks within intensively managed forests. Intensively managed pine supports diverse avian assemblages potentially affected by establishment and maintenance of a biomass feedstock. I sought to understand how establishing switchgrass on an operational scale affects bird communities within intercropped plantations as compared to typical intensively managed loblolly pine (Pinus taeda) plantations. I conducted breeding bird point counts, nest searching and monitoring, and coarse woody debris (CWD) surveys following establishment of intercropped switchgrass stands (6 replicates), traditionally-managed pine plantations, and switchgrass-only plots (0.1 km2 minimum) in Kemper Co., MS from 2011 to 2013. I found establishment of intercropping did not affect downed CWD, but reduced standing snags and green trees. I detected 59 breeding bird species from 11,195 detections and modeled nest survivorship for 17 species. Neotropical migrants and forest-edge associated species were less abundant in intercropped plots than controls for two years after establishment, and more abundant in year three. Short distance migrants and residents were scarce in intercropped and control plots initially, and did not differ between these treatments in any year. Species associated with pine-grass habitat structure were less abundant initially in intercropped plots, but converged with pine controls in subsequent years. Switchgrass monocultures provided minimal resources for birds. There was no evidence supporting an effect of intercropping on songbird nest survivorship. I found evidence for dominance of one species, yellow-breasted chat (Icteria virens), over another, indigo bunting (Passerina cyanea) in competition for nest sites, which illustrates how songbirds competing for nest sites can coexist in sympatry without the dominant species driving subordinate competitors to local extirpation. This dissertation, and related publications, are among the earliest research on wildlife response to intercropping. Forest managers implementing intercropping within pine plantations where vertebrate conservation is a management priority should be aware of potential changes to snag-utilizing species from reductions in green trees and snags. Songbird populations may lag behind traditional management for up to two years following establishment of switchgrass. Intercropping neither positively nor negatively affected songbird nest survival