Grassland bird response to patch burn-grazing in a sand sagebrush-mesquite rangeland
Yancey, Sean R.
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Wildlife in the Great Plains evolved with fire and grazing interacting spatially and temporally to create a shifting mosaic landscape comprised of severely disturbed habitats, undisturbed habitats, and patches that vary in time since the most recent disturbance. When given the choice, bison grazed on the most recently burned areas, much as they were suspected of doing prior to European settlement of the Great Plains. Currently, rangeland managers try to achieve uniform cattle distribution or uniform coverage by prescribed burning in an effort to utilize their resources as efficiently as possible. Additionally, these 2 types of disturbance are nearly always used apart from each other. This traditional rangeland management promotes homogeneity of vegetative communities and may have a critical impact on biodiversity and wildlife habitat. With the increased interest in using prescribed fire to manage Rolling Plains rangelands for wildlife and livestock we propose the effects of patch burning and grazing in sand sagebrush (Artemisia filifolia)-honey mesquite (Prosopis glandulosa) grassland will positively impact the diversity and abundance of grassland birds, particularly northern bobwhites (Colinus virginianus). This study was conducted within the Matador Wildlife Management Area (WMA), located in Cottle County, Texas approximately 10 km north of the town of Paducah, Texas in the Rolling Plains ecoregion from 2009-2011. My study site consisted of 619-ha of contiguous sand sagebrush-mesquite rangeland in the Entrance and Headquarters pastures of the Matador Wildlife Management Area (34.117721, -100.356536). The Entrance pasture was subjected to patch-burning with grazing as well as rotational grazing. The Headquarters pasture was subjected to patch-burning only. Vegetation and grassland birds were monitored throughout the entire study site, with northern bobwhites monitored for survival, home range, and nest success. Due to severe drought effects during the duration of the study, grass and forb cover was reduced from 2009 to 2011. Grassland bird species richness and abundance declined from 2009 to 2011. Northern bobwhite survival from 2009-2011 was 19%, 5%, and 36%, for respective years. Northern bobwhites did not use treatments proportionately more than what was available during any year. Mean home range size did not differ among years (P=0.0298). Pooled nest survival was calculated using ProgramMARK for the 24 day incubation period and was observed at 29%. The model with the covariates of percent residual cover at nest site, percent shrub cover at nest site, and proximity to edge resulted in the strongest model (AICc=0.0000). Patch burning-grazing did not positively benefit grassland birds or northern bobwhites. Consideration for drought conditions should be applied when trying to implement a patch burning-grazing system.