Hummingbird feeders are a popular way for people to attract and observe these energetic pollinators. However, the sugar water provided in these feeders may have an impact on the health of these tiny birds. A recent study from the University of California, Davis, is among the first to investigate the potential for sugar water to act as a carrier for pathogens affecting birds and potentially humans. The research indicates that while microbes are present, most do not appear to pose a significant health risk.
The study, published in the Proceedings of the Royal Society B, examined the microbial communities found in hummingbird feeder sugar water and compared them to those in natural flower nectar and samples taken directly from hummingbirds.
“While we discovered high concentrations of both bacteria and fungi in the sugar water from feeders, only a small number of these species have been documented as causing illness in hummingbirds,” stated Rachel Vannette, an assistant professor at UC Davis and co-author of the study. “Nevertheless, a small fraction of these microbes have been linked to diseases. Therefore, we strongly advise anyone providing feeders for hummingbirds to clean them regularly and to avoid cleaning them in areas where human food is prepared.”
The research, conducted at a private residence in Winters, California, focused on two species of hummingbirds: Calypte anna (Anna’s hummingbird) and Archilochus alexandri (black-chinned hummingbird). Scientists used drop-net feeder traps to capture the birds for sample collection.
The scientists investigated how different water sources affect microbial growth. They observed that when feeders were frequented by birds, deionized water fostered the most fungal growth, while tap water or bottled water supported the highest levels of bacterial growth.
Furthermore, the study revealed that birds, the sugar water in feeders, and natural flowers all hosted distinct bacterial and fungal communities.
“The type of microbes that hummingbirds consume is heavily influenced by their diet, specifically whether they rely on feeders or solely on floral nectar,” Vannette explained. “The long-term health implications for birds and their gastrointestinal flora remain unknown, but we believe further research is warranted given the widespread use of feeders and the opportunistic feeding habits of these birds.”
Understanding Avian Pollinators
Hummingbirds, belonging to the family Trochilidae, are among the world’s few avian pollinators. It is noteworthy that approximately 15 percent of hummingbird species are currently facing threats or are endangered.
“Although our study doesn’t directly address the health outcomes for hummingbirds, alterations in the microbial composition of a bird’s diet could potentially impact their microbiomes,” noted Lisa Tell, a professor in the Department of Medicine and Epidemiology at the UC Davis School of Veterinary Medicine and a co-author. “Moving forward, it will be crucial to understand how the microbial populations ingested by birds might influence the health of wild hummingbirds, especially considering human-induced environmental changes affecting wildlife.”
Tell emphasized that natural floral nectar is the optimal food source for hummingbirds. When feeders are provided, it is essential to adhere to best practices, which include routine and thorough cleaning to ensure no harmful residues are left behind.
This research paper, titled “Microbial Communities in Hummingbird Feeders Are Distinct from Floral Nectar and Influenced by Bird Visitation,” was authored by Casie Lee, a student at the UC Davis School of Veterinary Medicine, Tiffany Hilfer, an undergraduate student majoring in global disease biology, along with Tell and Vannette.
Casie Lee spearheaded the field experiment, conducted bird observations, and performed laboratory analyses as part of a summer project funded by the Students Training in Advanced Research (STAR) and Merial Veterinary Scholars Programs, under the mentorship of Vannette and Tell.
Regular cleaning of hummingbird feeders is paramount to ensure the birds’ health. By maintaining clean feeders and prioritizing natural nectar sources, we can help support these vital pollinators.
