Sedgwick and Knopf found that breeding densities of the migratory birds, in the study area, were not influenced by a seasonal, short-duration cattle (Bos taurus) grazing system. Sedgwick and Knopf note that birds dependent on overstory coverage may be influenced by the long-term effects of grazing on seedling survival and overstory tree species regeneration, since even moderate grazing can alter overstory composition, density, and demography. Avian productivity may also be reduced by the effects of grazing, even though avian densities in the short-term are seemingly unaffected. Since the common yellowthroat (Geothlypis trichas) and yellow-breasted chat (Icteria virens) selected habitats with the most vegetation coverage and density, they seem to be most impacted by herbage removal from grazing. American robins (Turdus migratorius), that choose habitat with less vegetation coverage and density, were least impacted by herbage removal from grazing. These results suggest that the common yellowthroat and yellow-breasted chat would be the best grazing pressure indicators for this study area.
Citations and enhanced abstracts for journals articles and documents focused on rangeland ecology and management. RSIS is a collaboration between Montana State University, University of Idaho, and University of Wyoming.