PS 2-22
Arthropods in restored riparian zones: the lower Colorado River and suitability for Southwestern Willow Flycatcher
The southwestern willow flycatcher (Empidonax traillii extimus) is a generalist insectivore that visits the Southwest USA during the summer for nesting. This small bird is a species of concern in the American southwest, and was listed as endangered in 1995. The flycatcher has been one of the main species of concern in restoration programs such as that of the lower Colorado River Multi Species Conservation Program, which has been establishing willow-cottonwood plantations to provide native habitat for threatened and endangered species. Because of flow regulation, channel incision, and levees, these floodplain plantations are disconnected from the river and plantings are sustained through irrigation. Nesting flycatchers have not been found in the restoration sites. We tested if these constructed riparian habitats had a similar insect community as river-formed reference riparian habitats where the flycatcher does nest. We implemented sticky trap sampling over the summer of 2013 at thirteen locations along the lower Colorado River (restored and not restored) and Bill Williams River (natural riparian habitat) in Arizona.
Results/Conclusions
We found higher densities of aquatic arthropods (such as dipterans, trichopterans, and ephemeropterans) at sites closest to the water, as well as higher densities of arthropods in general. Our results indicate that the flycatcher may not be nesting at restoration sites because of a lack of preferred prey, and previous studies have documented that nestlings rely on a larger portion of aquatic insects (especially dipterans). Considering many of the recent riparian restoration sites are well over 100m from the river’s edge, and that these sites have not been successful nesting sites, our results suggest that future restoration projects should consider prey availability and proximity to the river in order to achieve functional habitat.