Native Bird Responses to Tamarisk (Tamarix Spp.) Biological Control: Implications for Southwestern Riparian Habitat and Management
Sean M. Mahoney1*, Matthew J. Johnson2, Jennifer A. Holmes3
1Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, USA; Sean.Mahoney@nau.edu
2Colorado Plateau Research Station, Northern Arizona University, Flagstaff, AZ, USA; Matthew.Johnson@nau.edu
3Colorado Plateau Research Station, Northern Arizona University, Flagstaff, AZ, USA; Jennifer.Holmes@nau.edu
Tamarisk (Tamarix spp.) are among the most successful non-native invasive plants in southwestern United States riparian systems and tamarisk control has become a high management priority in the southwest. In 2001, the tamarisk leaf beetle (Diorhabda carinulata) was released as a biological control agent to control tamarisk. Since 2001, tamarisk leaf beetles have spread throughout the southwest including riparian habitat previously thought to be inhospitable. The primary effect of tamarisk leaf beetles on tamarisk is defoliation, and this can potentially change habitat structure and insect food base for riparian nesting birds. Unfortunately, little information is available on how birds respond to the tamarisk leaf beetle and the changes it causes to riparian areas, but these data could be important for management purposes. During the summer of 2013 and 2014 we used point counts to quantify avian abundance, density and richness in areas that varied in the amount of native vegetation and tamarisk defoliation along the Virgin River. We found bird abundance, density and richness were positively correlated with percentage of native vegetation cover and were negatively correlated with percentage of tamarisk defoliation. Our results highlight the need for active restoration in areas where tamarisk defoliation has occurred to maintain bird abundance, density and richness along riparian systems in the southwest.