Evaluation of patch-burn grazing on species richness and density of grassland birds
Document Type: Thesis
Author(s): David J. Stroppel
Publication Year: 2009

Cataloging Information

  • fire
  • grassland
  • grassland birds
  • grazing
  • Great Plains
  • Missouri
  • patch burn grazing
  • species density
  • species richness
Record Maintained By:
Record Last Modified: November 12, 2015
FRAMES Record Number: 18051


When European settlers arrived in North America they found large, unfragmented, tallgrass prairies. This historic presettlement prairie ecosystem in Missouri has been described as a tallgrass plant community that was subject to frequent fire and grazing with few trees and shrubs (Kurz 2003, Nelson 2005). Mechanized agriculture converted much of the prairie into crop fields, fragmenting the prairie, reducing the prevalence of fires and shrinking the tallgrass prairie to 5% of its presettlement range (Sampson and Knopf 1994). Today, only about 36,000 hectares (90,000 acres) of Missouri's original 6 million hectares (15 million acres) of prairie still exist (Kurz 2003). Along with the loss of the tallgrass prairie, grassland bird populations have undergone dramatic declines in spite of management efforts. The North American Breeding Bird Survey data show that 70% of the 29 bird species characteristic of North American prairies declined between 1966 and 1993. These grassland bird species are declining faster than any other guild of terrestrial birds on this continent (Knopf 1994). This suggests that techniques currently used to manage rangelands may be insufficient to maintain biological diversity (Holecheck et al. 1998). To reverse this decline, the remaining tracts of tallgrass prairie must be managed in a way to provide the diverse habitat needs of the avian community. The presence of grazing during the evolution of prairie ecosystems helped promote biodiversity. This suggests that biodiversity could be enhanced on today's grasslands by mimicking the temporal and spatial grazing patterns of presettlement prairies (Fuhlendorf and Engle 2001). Heterogeneity when defined as variation in vegetation structure, composition, density and biomass, influences species diversity, habitat variety and ecosystem function (Christensen 1997, Wiens 1997, Bailey et al 1998). Many species depend on the interspersion of diverse habitat types scattered throughout a heterogeneous landscape (Fuhlendorf and Engle 2001). Heterogeneity leads to biodiversity and should serve as the framework for ecosystem management (Christensen 1997, Ostfeld 1997, Wiens 1997). The variation in habitat requirements of grassland birds shows us that heterogeneity is important. The structure of grassland avian communities is influenced by the structural heterogeneity of the plant communities (Wiens 1974). Certain bird species require specific structural characteristics in grasslands (Cody 1985). The variation in habitat requirements of coexisting grassland bird species supports the necessity of heterogeneous grasslands for maintaining diverse avian communities (Fuhlendorf and Engle 2001). For example, Greater Prairie Chickens (Tympanuchus cupido) need short, sparsely vegetated ground for courtship displays, sites with residual vegetation for nesting, and, in general, little woody vegetation (Johnson et al. 2004). Upland Sandpipers (Bartramia longicauda) use short vegetation for foraging, short to medium height vegetation for brood rearing, and taller vegetation for nesting (Johnson et al. 2004). Grasshopper Sparrows (Ammodramus savannarum) prefer short to intermediate height, clumped grasslands interspersed with patches of bare ground for foraging and for nesting they require moderate amounts of litter (Bent 1968, Blankespoor 1980, Vickery 1996). The Eastern Meadowlark (Sturnella magna) prefers intermediate height grasslands with a moderate amount of forbs and little woody vegetation. The meadowlark forages for insects on the ground or in the soil and nests on the ground within short grasslands that are moderately to heavily grazed (Skinner et al 1984). These species, and others, prefer different habitats for different stages of their life cycle, and often they need these habitats in close proximity to one another. To achieve this mix of habitats, juxtaposed in such a way as to benefit several different species; a mix of management techniques is needed that mimic the interaction of historic processes that shaped prairies. The eastern tallgrass prairie community evolved under the interactive effects of climate, topography, soil types and conditions, fire, and grazing (Axelrod 1985). The combined effects resulted in diverse plant communities of grasses and forbs in different successional stages scattered across the landscape. Today, large contiguous tracts of native prairie are rare, and managers are trying to replicate the interaction of fire and grazing on relatively small, isolated patches of native and restored prairie. These smaller prairies may function differently than larger prairies of presettlement times, but the historical processes of fire and grazing are still necessary to maintain functioning prairie systems. One promising prairie management technique is patch-burn grazing (PBG). PBG mixes annual burning with summer grazing to increase vegetation heterogeneity. This technique may help create the mix of plant communities similar to what occurred historically. PBG created diverse plant structure scattered across the landscape (Fuhlendorf and Engle 2001) and has potential for enhancing grassland bird populations. The benefits of PBG to grassland bird populations versus burning alone have not been tested in Missouri. It has been investigated in other states with promising results. Our overall objective was to conduct a confirmatory analysis of the effects of PBG on species richness and density of grassland birds. The diversity in vegetative structure created by PBG, should lead to greater species richness, and higher densities for some species (e.g. Grasshopper Sparrow). We expect estimated density will be greater in the control unit for the DICK and HESP and greater in the grazing unit for EAME and GRSP. We will use a student's t-test to check for significant differences in mean estimated density. It is the goal of this study to determine where avian species richness and density is higher relative to the treatment effects from grazing, years since burning and the interaction of grazing and years since burning. This information could prove valuable to managers who wish to provide habitat conditions for a large suite of grassland birds but are concerned about making the lands they manage unsuitable to the species that are currently present or to species of conservation concern.

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Link to this document (1.4 MB; pdf)
Stroppel, David J. 2009. Evaluation of patch-burn grazing on species richness and density of grassland birds. Master of Science. Columbia, MO: University of Missouri-Columbia. 40 p.