Date of Award
Doctor of Philosophy
David Buehler, Joseph Clark, Andrew Griffith, Travis Mulliniks
Eastern grassland bird populations have been declining since the Breeding Bird Survey was initiated in 1966. The cause of the decline is the near-complete loss of their native grassland habitats. A driver of the loss of native grasslands in the East is the conversion of native grasses to the introduced species tall fescue (Lolium arundinaceum). Tall fescue, a cool-season grass, provides livestock forage during fall and spring, but does not provide habitat for most grassland bird species due to its dense, sod-forming structure. Wildlife biologists have recommended the incorporation of native warm-season grass (NWSG) pastures into grazing systems as a solution to the grassland bird decline that will also benefit beef cattle producers. However, little data exists on the efficacy of this practice for grassland bird conservation or beef cattle production when pastures are managed the way a typical producer is likely to manage them, with continuous, season-long (May – August) grazing. I designed an experiment to compare grassland bird density and nest survival in NWSG cattle pastures among two continuous, season-long stocking strategies: continuous (CONT) and heavy-early (HEAVY), and traditionally-managed tall fescue pastures (FESCUE) during summers 2015 – 2017. Animal performance of weaned steers, pasture production, and sward sustainability were recorded throughout the study. I developed an enterprise-level economic model to determine the impact of incorporating the perennial warm-season grasses switchgrass (Panicum virgatum) and bermudagrass (Cynodon dactylon) on profitability of beef cattle operations in the Fescue Belt. Grasshopper sparrow (Ammodramus savannarum) density was three times greater in NWSG (0.30 males/ha) than FESCUE pastures (0.11 males/ha), and both species selected to nest in NWSG and selected against nesting in FESCUE pastures. Average daily gain of steers was similar between CONT (0.98 kg/d) and HEAVY (0.89 kg/d) and was comparable to other NWSG grazing studies, and both stocking strategies were sustainable over the study period. Incorporating switchgrass into simulated tall fescue forage systems increased profitability over 100% fescue systems by 1,070% and 42% for spring- and fall-calving herds, respectively. The results of my study indicate that continuously-grazed NWSG pastures in the Fescue likely contribute to both grassland bird conservation and beef cattle production.
Brazil, Kyle, "Avian Density and Nest Survival and Beef Production on Continuously-Grazed Native Warm-Season Grass Pastures. " PhD diss., University of Tennessee, 2019.