Small-Scale Woodland Reduction Practices Have Neutral or Negative Short-Term Effects on Birds and Small Mammals

Abstract

Woodland reduction has been under way for decades to improve habitat for certain wildlife species, increase forage for livestock, improve watershed function and reduce soil erosion, and increase plant community heterogeneity. Land managers have implemented a variety of techniques to reduce woodlands. Yet most studies on outcomes are observational and focus on plant communities; fewer studies experimentally compare the relative effects of woodland reduction methods on wildlife. We conducted an experiment to evaluate the effects of three mechanical tree removal methods on habitat use by native birds and abundance of small mammals in the first 2 yr after treatment. Located in the Piceance Basin, Colorado, United States, this study consisted of seven replicated 1-ha stands of pinyon-juniper woodland treated with chaining, roller-chop, hydro-ax, as well as untreated plots (n = 28 plots). We found no differences in initial bird habitat use or small mammal abundance among the woodland reduction treatment methods. However, we found evidence that habitat use was significantly lower in all woodland reduction treatment plots than in control plots for birds of dense woodland and open woodland habitats, and that use was positively associated with tree cover. Furthermore, no grassland or shrubland obligate birds used the treatment plots, suggesting that small-scale woodland reduction treatments may not provide attractive habitat for shrubland or grassland birds, at least within 2 yr following treatment. Because some bird species responded negatively to all methods of woodland reduction treatments, and no bird or small mammal species responded positively, the initial effects of small-scale chaining, roller-chop, and hydro-ax treatments on wildlife should not be overlooked.