Interactions Between Tamarisk, Russian Olive, Birds, and Biological Control
Sean Mahoney*1
1Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, sean.mahoney@nau.edu
Non-native plant introductions may alter the structural composition and the biotic and abiotic components within a habitat, potentially changing the relative value for the broader community. In the western US, tamarisk (Tamarix spp.) and Russian olive (Elaeangnus angustifolia) are two non-native plants that have become extensively naturalized along rivers. Tamarisk and Russian olive are hypothesized to have negative consequences for native flora and fauna and therefore, managing these non-natives is a conservation priority. Native birds may be particularly at risk, because birds disproportionately use riparian habitats. One management approach is biological control (biocontrol), which uses a natural enemy to suppress an invasive species. In the tamarisk system, the folivorous insect, Diorhabda spp., is used as biocontrol. Since the initial release, Diorhabda have spread widely, including into riparian habitat originally believed to be uninhabitable by the beetle. Understanding how tamarisk defoliation affects native birds, their arthropod prey, and abiotic factors like temperature and humidity that could affect nest success, is critical for management. Despite the potential for Russian olive establishment in new riparian habitats, much of its ecology remains unclear, in particular, how Russian olive affects native bird communities. Studies comparing bird use of native and Russian olive habitats are especially limited. Although no biological control has been released for Russian olive, a mite (Aceria angustifoliae) has been identified as a candidate, so a more complete understanding of Russian olive is important for effective management. We will present 1) data showing how tamarisk biocontrol affects native birds and 2) data that fill an important knowledge gap on bird responses to Russian olive naturalization.