Livestock grazing can degrade riparian vegetation, altering habitat for many species of declining migratory breeding birds. At Hart Mountain National Antelope Refuge in southeastern Oregon, cattle were removed from riparian areas in 1990 after 120 years of grazing.
This offered an opportunity for USGS researchers to evaluate whether passive habitat restoration on riparian breeding grounds resulted in increases of migratory bird species. Overall avian abundance increased 23 percent during the 12 years after removal and remained consistent from then through year 24. Of the 20 focal species studied, birds that depended on riparian trees or shrubs were most positively affected by cattle removal, increasing in abundance and contradicting regional declining trends. Cavity nesting birds decreased in abundance locally, likely reflecting the lack of mature, rot-infected trees that were scarce because of decades of grazing. Restoring riparian ecosystems by removing livestock appeared to benefit many declining populations of migratory birds of conservation concern in the arid western United States.
Poessel, S.A., Hagar, J.C., Haggerty, P.K., Katzner, T.E., 2019, Removal of cattle grazing correlates with increases in vegetation productivity and in abundance of imperiled breeding birds: Biological Conservation, v. 241, p. 108378, https://doi.org/10.1016/j.biocon.2019.108378.