Friday Flash - Impacts of historical disturbance regimes
on avian conservation in eastern tallgrass
prairies

JFSP PROJECT ID: 20-1-01-24

Researchers: Antonio Del Vallé & Holly P. Jones (Northern Illinois University) 

Grazing from native herbivores such as bison, in combination with prescribed fire, are applied to tallgrass prairies by managers to recreate important disturbance regimes in this ecosystem. Bird communities may be indirectly impacted by these disturbances, as bison and prescribed fire alters the structure of critical breeding habitat for grassland birds. The objectives of this research are to determine the impacts that bison and prescribed fire have on grassland breeding birds in two tallgrass prairie preserves, Kankakee Sands and Nachusa Grasslands. Bird communities, vegetation structure, bison activity and prescribed fire history were surveyed systematically at these two preserves in 2020 and 2021. Researchers found that disturbance regime type impacted bird community composition more than interannual variation or preserve location. Bird species richness was highest within management units that were unburned, regardless of bison presence, in comparison to burned units without bison. Vegetation structure had the largest impact on grassland obligate bird abundances, with grazing and fire disturbances having larger impacts than restoration planting age and spatiotemporal factors. Researchers also found that the interactive grazing patterns of bison in response to prescribed fire (pyric herbivory) may be impacting two grassland bird species in ways that have not been previously described. These results highlight the importance of applying varying levels of grazing and fire disturbance in order to provide a heterogeneous landscape with variable vegetation structure to accommodate the life history preferences of a diversity of grassland bird species. Species-specific preferences of disturbance intensity and vegetation structure may be used to manage for particular species of conservation concern at these preserves and throughout the region.