Removal pattern mitigates negative, short‐term effects of stepwise Russian olive eradication on breeding birds

Abstract

Abstract Invasive species can have disastrous ecological consequences, and management is often required to control these invasions and mitigate the damage. Yet in many systems, biological invaders can serve critical ecological roles, particularly where they have been long‐established or effectively replaced functionally similar native species. In such cases, eradicating invasions can have unintended consequences on other components of the ecosystem, and potential control measures must be viewed within an ecosystem‐wide context to ensure they do not cause more harm than good. On the lower Snake River in eastern Washington, invasive Russian olive (Elaeagnus angustifolia) comprises 90% of the woody riparian vegetation in some areas. In this study, we experimentally removed half of the Russian olive from 0.5‐ha plots using three configuration patterns that varied in the amount of interspersion of remaining vegetation (n = 9 replicates) to evaluate the short‐term impact of a stepwise restoration strategy on breeding bird communities. We monitored plots for 5 yr and found that Russian olive removal on low interspersion treatments negatively affected occupancy rates for 50 of 52 species (96%) and significantly reduced richness by up to 2.41 (95% credible interval [CI] = 0.73, 4.14) species relative to control plots. These effects dampened with increasing interspersion, and occupancy rates of only 41 (79%) species decreased on high interspersion treatments, leading to non‐significant richness reductions of only 0.99 (95% CI = −0.70, 2.75) species. Given the dominance of Russian olive in this region, removing it eliminates critical habitat for birds that require woody structure for nesting and foraging. Thus, we caution managers to consider the potential short‐term negative impacts to the local fauna when planning invasive control efforts. However, we found that several riparian‐dependent species known to breed in the region were noticeably absent from our study plots, and short‐term losses in avian habitat may be tolerable where restoration of native vegetation supports greater diversity in the long term. In such restoration efforts, managers may be able to mitigate the negative effects of invasive shrub control by maintaining high interspersion among unmanipulated vegetation while waiting for native vegetation to re‐establish.

Keywords

• avian diversity
• breeding birds
• community occupancy model
• ecosystem perspective
• Elaeagnus angustifolia
• invasive plant control