Microbial communities in hummingbird feeders are distinct from floral nectar and influenced by bird visitation

Human provisioning can shape resource availability for wildlife, but consequences for microbiota availability and exchange remain relatively unexplored. Here, we characterized microbial communities on bills and fecal material of two hummingbird species and their food resources, including hummingbird feeders and floral nectar. We experimentally manipulated bird visitation to feeders and examined effects on feeder microbial communities and sucrose solutions. Birds, feeders, and flowers hosted distinct bacterial and fungal communities. Flowers and feeders hosted remarkably different bacterial communities; Proteobacteria comprised over 80% of flower bacteria but feeders contained high relative abundance of Proteobacteria, Firmicutes and Actinobacteria. Birds hosted both bacterial taxa commonly found in other bird taxa, novel genera including Zymobacter [Proteobacteria], and Ascomycete fungi. In feeders, bird-visited and unvisited solutions both accumulated abundant microbial populations tha...