Tamarisk Biocontrol Using Tamarisk Beetles: Potential Consequences For Riparian Birds in the Southwestern United States

Abstract

The tamarisk beetle {Diorhabda spp,), a non-native bioeontrol agent, has been introduced to eradicate tamarisk (Tamarix spp,), a genus of non-native tree that has become a dominant component of riparian woodlands in the southwestern United States, Tatnarisk beetles have the potential to spread widely and defoliate large expanses of tamarisk habitat, but the effects of such a widespread loss of riparian vegetation on birds remains unknown. We reviewed literature on the effects of other defoliating insects on birds to investigate the potential for tamarisk beetles to affect birds positively or negatively by changing food abundance and vegetation structure. We then combined data on the temporal patterns of tamarisk defoliation by beetles with nest productivity of a wellstudied riparian obligate, the Southwestern Willow Flycatcher (Empidonax traillii e.xtimus), to simulate the potential demographic consequences of beetle defoliation on breeding riparian birds in both the short and long term. Our results highlight that the effects of tamarisk bioeontrol on birds will likely vary by species and population, depending upon its sensitivity to seasonal defoliation by beetles and net loss of riparian habitat due to tamarisk mortality. Species with restricted distributions that include areas dominated by tamarisk may be negatively affected both in the short and long term. The rate of regeneration and/or restoration of native cottonwoods (Populus spp,) and willows (Salix spp,) relative to the rate of tamarisk loss will be critical in determining the long-term effect of this large-scale ecological experiment. Control Biológico del Tamarisco por el Escarabajo del Tamarisco: Consecuencias Potenciales para las Aves Ribereñas en el Sudoeste de los Estados UnidosResumen. El escarabajo del tamarisco (Diorhabda spp,), un agente de control biológico no nativo, ha sido introducido para erradicar al tamarisco (7awor/.r spp,), un género de árbol no nativo que se ha vuelto un componente dominante de los bosques ribereños en el sudoeste de los Estados Unidos, Los escarabajos del tamarisco tienen el potencial de dispersarse ampliamente y defoliar grandes extensiones del habitat del tatnarisco, pero no se conocen los efectos de una pérdida tan extensa de vegetación ribereña sobre las aves. Revisamos la literatura sobre los efectos de otros insectos defoliantes sorbe las aves para investigar el potencial de los escarabajos del tamarisco de afectar positiva o negativamente a las aves mediante el cambio en la abundancia de alimentos y en la estructura de la vegetación. Combinamos luego los datos de los patrones temporales de defoliación del tamarisco producidos por los escarabajos con la productividad de los nidos de una especie ribereña obligada bien estudiada, Empidonax trailla extimus. Simulamos las consecuencias demográficas potenciales de la defoliación de los escarabajos sobre las aves ribereñas reproductivas tanto al corto como al largo plazo. Nuestros resultados destacan que los efectos del control biológico del tamarisco sobre las aves...

Evaluation of NDVI to assess avian abundance and richness along the upper San Pedro River

“…However, willow and mesquite were also found only in small quantities at our sites, with only 40 points being 10% or more covered by willow and zero points having that much mesquite, yet the effects of these trees were still important in multiple models. Tamarisk is generally considered to have low arthropod abundance and a less diverse arthropod community compared to native vegetation (DeLay et al, 1999;DeLoach et al, 2000;McGrath et al, 2009;Yard et al, 2004), and there is still much debate over the role of tamarisk as habitat for birds (Cersale and Guglielmo, 2010;Paxton et al, 2011). Therefore, the effect of tamarisk on birds is less important than are other native plant species as has been shown on the Colorado River by van Riper et al (2008).…”

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