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SFS Annual Meeting

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Stable isotopes reveal invasion-mediated changes in aquatic subsidies provided to riparian songbirds

Non-native plant introductions can impact riparian ecosystem function through diverse terrestrial and aquatic pathways, resulting in cascading effects throughout food webs. Invasion-mediated vegetation changes have been shown to depress terrestrial arthropod communities and alter arthropod flux across the aquatic-terrestrial interface. We investigated the effects of a non-native woody plant, New Mexico locust (Robinia neomexicana), on insect contributions to riparian songbird diets. Using stable isotope analyses of insects and avian feces, we found the riparian songbird community consumed approximately 34% aquatic resources, highlighting the importance of aquatic resource subsidies to riparian consumers. Additionally, we found evidence that two insectivorous bird species consumed more aquatic insects in invaded sites, but these invasion-mediated diet shifts differed among years. Our detection of changes in terrestrial- and aquatic-derived prey in bird diets in response to a near-range plant invasion suggests that the introduction of invasive alien species from more geographically isolated native ranges could produce similar or stronger effects. Resource subsidies hold great potential as a means of understanding indirect consequences of invasion for riparian consumers.

Hannah Riedl (Primary Presenter/Author),;

Lani Stinson ( Co-Presenter/Co-Author);

Liba Pejchar ( Co-Presenter/Co-Author), hidsodhf;