If you build it, who will come? Landbird response to riparian restoration at the San Joaquin River National Wildlife Refuge

Biodiversity loss under human landscape alteration is often sought to be reversed through ecological restoration. Most restoration projects focus on restoring habitat by reintroducing elements of the native flora, letting the remaining plant and animal species from the native community return on their own. Research / monitoring efforts therefore emphasize rapid recovery of ecosystem processes, and have only recently begun addressing recovery of functional groups and community assembly. Such engineered habitats are an underexploited opportunity for ecologists to understand the basic processes underlying community assembly, and to follow a community’s long-term trajectory. Here we examine avian responses, specifically community assembly, to riparian restoration along the San Joaquin River in the Central Valley of California. We use point counts and vegetation assessment to investigate bird habitat relationships and seasonal habitat use patterns. Preliminary results from 2006 (four years post restoration) show increases in vegetation height, cover, and structural complexity, and that cultivated riparian forests appear to be supporting a diverse avian community. Bird species richness ranges from 6 to 13 (total of 23) in the summer and 3 to 12 species per point in the fall (total 21). In the summer the most abundant functional groups were ground granivores and insectivores, followed by foliage insectivores, bark insectivores, aerial insectivores, and generalist omnivores. In the fall ground granivores were the most abundant functional group followed by bark insectivores, aerial insectivores, ground insectivores, foliage granivores, and generalist omnivores. Results from our ongoing study provide a baseline for monitoring the reassembly of this riparian forest community, now likely to experience greater management inputs under new agreements to restore the San Joaquin River, and provide insights into the process of community assembly in engineered habitats.