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Non-native plants can impact riparian ecosystem function through diverse terrestrial and aquatic pathways, with cascading effects on food webs. Invasion-mediated vegetation changes can depress terrestrial arthropod communities and alter arthropod flux across the aquatic-terrestrial interface. We investigated the effects of a non-native woody plant, Robinia neomexicana, on insect contributions to riparian songbird diets. This plant was introduced over 100 years ago to the Clear Creek drainage in northwestern Colorado (USA) from its native range, which extends into southern Colorado. We used stable isotope analysis of insects and avian feces to 1) assess whether the relative contributions of aquatic- and terrestrial-derived arthropod prey differed between reference sites and sites invaded by R. neomexicana, and 2) quantify the amount of aquatic- and terrestrial-derived resources consumed by an insectivorous songbird assemblage. Two species of insectivorous songbirds consumed more aquatic insects in invaded sites compared to reference sites. This change in terrestrial- and aquatic-derived prey in bird diets in response to a near-range plant invasion suggests that the introduction of novel species from more distant native ranges could produce similar or stronger effects. Overall, the songbird community consumed approximately 34% aquatic resources, which highlights the importance of these subsidies to riparian consumers. Our investigation of insect subsidies demonstrates how introduced species can indirectly affect food webs and provides insight into the plasticity of riparian consumer responses., Competing Interests: This research was financially supported by Chevron Corporation, Colorado Field Ornithologists, the Warner College of Natural Resources, and the Graduate Degree Program in Ecology at Colorado State University. Funding provided by these partners does not alter our adherence to PLOS ONE policies on sharing data and materials. We have no opposition to or conflicts with editorial board members, nor any further conflicts of interest to disclose.