Most Microbes in Hummingbird Feeders Do Not Pose Health Hazard

Feeders or Flowers? Researchers Compare Microbes

Reading Time: 2 minutes

We enjoy setting up hummingbird feeders in our yards to nurture and watch these high-energy pollinators.

But did you ever wonder if the sugar water we provide is impacting these tiny feathered friends?

The University of California, Davis is one of the first to address the potential for sugar water from hummingbird feeders to act as a vector for avian — or even zoonotic — pathogens.

Not a Significant Health Hazard

The study found that the majority of microbes growing in feeders do not likely pose a significant health hazard to birds or humans.

Scientists explored the microbial communities that dwell in sugar water from feeders and compared them to those found in flower nectar and samples from live hummingbirds.

If you provide hummingbird feeders be sure to to clean them regularly and avoid cleaning feeders in areas where you prepare food
If you provide hummingbird feeders be sure to to clean them regularly and avoid cleaning feeders in areas where you prepare food

Rachel Vannette, community ecologist, co-author, and assistant professor in the UC Davis Department of Entomology and Nematology says that although they found high densities of both bacteria and fungi in sugar water samples from feeders, very few of the species found have been reported to cause disease in hummingbirds.

She says that a tiny fraction of those microbes have been associated with disease.

“So we encourage everyone who provides feeders for hummingbirds to clean their feeders regularly and to avoid cleaning feeders in areas where human food is prepared,” Vannette adds.


Ruby-throated Hummingbird on its nectar feeder
Ruby-throated Hummingbird on its nectar feeder

Diet Affects Microbes

The UC Davis scientists conducted their research at a private residence in Winters, California, attracting two hummingbird species, Calypte anna (Anna’s hummingbird) and Archilochus alexandri (black-chinned hummingbird) to drop-net feeder traps.

They assessed how water type influences microbial growth.

When feeders were exposed to birds, they found that deionized water supports the most fungal growth while tap water or bottled water supports the most bacterial growth.

They also found that birds, feeder sugar-water, and flowers hosted distinct bacterial and fungal communities.

“The microbes that hummingbirds are eating depend a lot on bird diet — if they have access to feeders or are just consuming floral nectar,” says Vannette.

Vannette says the scientists don’t know what the consequences are for bird health or gastrointestinal flora.

But they think that there should be more studies examining this, as many, many people use feeders, and the birds are opportunistic and drink from feeders.

The best food source for hummingbirds is floral nectar
The best food source for hummingbirds is floral nectar

Avian Pollinators

Hummingbirds (family Trochilidae) are one of the world’s few avian pollinators.

Nearly 15 percent of hummingbird species are threatened or endangered.

Lisa Tell, co-author, and professor in the UC Davis School of Veterinary Medicine’s Department of Medicine and Epidemiology says that although the study does not directly inform hummingbird health outcomes, shifts in microbial composition in bird diets may influence bird microbiomes as a consequence.

“In the future, it will be important to understand how consumed microbial populations could potentially influence the health of free-ranging hummingbirds, particularly with regards to human-caused effects on wildlife,” shel adds.

Tell says the best food source for hummingbirds is floral nectar.

If you put out hummingbird feeders for these high-energy pollinators, sherecommends making it a routine to thoroughly clean your feeders so that you don’t have harmful residues.

Read the University of California, Davis research published March 6 in the Proceedings of the Royal Society B.


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