Influence of Tamarisk Invasion on Bird Populations

Authors: Harmon, Daniel - Dan; Young, James; Longland, William - Bill

Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/25/2006
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Determining the effects of exotic species invasion on native plant and animal communities is of great value for land and wildlife managers. With limited resources always a concern, defining the greatest threat of an invasion is important. In desert environments of the Great Basin, riparian woodlands are ecologically unique in an otherwise treeless environment. Tamarisk (Tamarix ramosissima Ledeb.), also known as saltcedar, is an exotic and invasive plant that has invaded thousands of hectares of riparian habitats in the western United States. After tamarisk establishment, the regeneration of native tree species critical habitat is often absent. Our purpose was to examine whether or not tamarisk supports similar bird communities when the native plant communities are invaded and converted to tamarisk dominance. We measured bird abundance and species richness over 2 years in paired native and tamarisk dominated desert riparian woodlands along two Great Basin river systems that have been treated with a biological control agent. In general, as one might predict, increases in the disparity of plant community structure between sites resulted in a greater difference of abundance and species richness of birds between the sites. Interestingly, comparing bird guilds, native plant dominated habitats harbored more foliage foraging, seed eating species, while tamarisk preferentially harbored more ground foraging, grassland, and shrub nesting species. Commonly observed human commensal species, such as the American crow (Corvus brachyrhynchos), black billed magpie (Pica pica) and the mourning dove (Zenaida macroura) significantly occurred more often in tamarisk habitats than native habitats. In native habitat, many riparian thicket nesting species, such as the red-winged blackbird (Agelaius phoeniceus) and yellow warbler (Dendroica petechia) occurred more often. The most conspicuous difference was a lack of large raptor and cavity-nesting species relating to the lack of a larger tree stem diameter in tamarisk habitat.