• Effects of continuous grazing on habitat and density of ground-foraging birds in south Texas

      Baker, D. L.; Guthery, F. S. (Society for Range Management, 1990-01-01)
      We analyzed the response of the key habitat features and ground-foraging birds to 2 intensities of continuous grazing on sandy loam and clay soils in the Texas Coastal Bend during 1984-1985. Heavy continuous grazing increased the dispersion but not necessarily the availability of bare ground in comparison with moderate continuous grazing. Responses of habitat features (structure of ground cover, key food plants) depended on soil type. Seasonal densities of eastern meadowlarks (Sturnella magna) were higher on clay than on sandy loam soils and higher under moderate than under heavy grazing. Mourning doves (Zenaida macroura) were more abundant on sandy loams than on clays and more abundant under heavy than under moderate grazing. Northern bobwhite (Colinus virginianus) abundance was uniformly low, regardless of grazing intensity and soil type.
    • Evaluation of Deer Habitat on a Nutritional Basis

      Wallmo, O. C.; Carpenter, L. H.; Regelin, W. L.; Gill, R. B.; Baker, D. L. (Society for Range Management, 1977-03-01)
      Protein and energy requirements of deer and supplies of these nutrients in native forage are synthesized into a model to estimate carrying capacity of seasonal ranges of a migratory mule deer population in north central Colorado. The model indicates that summer forage will support many times the number of deer present, but winter forage will not sustain deer at any population level. Instead, duration and severity of winter determine the length of time deer can survive on these ranges. Habitat evaluation based on quantification of nutrient supplies and their availability offers a more logical alternative for evaluating deer winter ranges than traditional methods based on measurements of twig lengths of so-called "key" species.
    • In Vitro Digestion—Sources of Within- and Between-Trial Variability

      Milchunas, D. G.; Baker, D. L. (Society for Range Management, 1982-03-01)
      Procedures for, and conditions during, inoculum collection and preparation, digestion, and residue recovery stages of the in vitro digestion technique were investigated to determine sources of within- and between-trial variability in digestion coefficients for forages of different chemical composition. Digestion coefficients differed significantly among inoculum preparation times of 1, 2, and 4 hours and for a decline in rumen fluid temperature to 29° in transport. These differences were not uniform across forage species and did not correlate with forage digestibility. Digestion coefficients differed significantly among inoculums prepared from fibrous deer rumen fluids that were strained only, strained and layered, and blended in a Waring blender and filtered through glass wool but did not differ between strained-layered and blended filtered inoculums of non-fibrous rumen fluid from a fistulated cow. Forage in vitro digestion in the absence of microbial activity (by solubility alone) indicated that forages having more soluble components were least affected by inoculums of different microbial activities, suggesting that between-trial differences be adjusted by a solubility, rather than a digestibility, factor. Inoculum nitrogen concentration did not correspond to between-trial differences in forage digestibility. Size of test tube, but not centrifugation versus filtration method of residue preparation, significantly affected digestion coefficients. However, because the standard large tube size cannot be centrifuged, the two methods of residue recovery would not be comparable unless the products of digestion were transferred from large tubes to centrifuge tubes. The end products of digestion must be stored under refrigeration if filtering proceeds for extended periods of time.