Hummingbird feeders are hard to miss. They're designed that way to entice hummingbirds to visit.

But it's easy to forget about maintaining the feeder. Sure, you refill it, but do you clean it? If not, are you doing more harm than good for the tiny birds?

Rest a little easy if you're lax about cleaning it. A study led by researchers at the University of California, Davis, finds that hummingbird feeders probably aren't the source of pathogens that could harm the birds or even other animals, but you should still clean the feeder on a regular basis.

Microbes everywhere

Microbial communities, like groups of pathogens, are everywhere, and they vary from location to location and body to body. In this case, the birds themselves, the feeders we put out for them and the flowers they seek out all have unique microbial communities of bacteria and fungus. The communities interact with each other as the birds move from source to source.

For this study, researchers attracted two different hummingbird species — Anna's hummingbird (Calypte anna) and black-chinned hummingbird (Archilochus alexandri) — at a private residence in Winters, California, to determine how different types of water influenced microbial growth. They found that deionized water in feeders resulted in more fungal growth, while tap and bottled water encouraged bacterial growth.

Hummingbirds and flowers tended to retain microbes often found with their respective species. So hummingbirds had bacteria on their beaks or in their fecal matter that were found in other birds. Flowers demonstrated the same kind of species-specific consistency.

According to researchers, the bacteria and fungal communities that researchers found in feeders aren't the kind that result in illnesses for the tiny birds.

An Anna's hummingbird drinks nectar from a Nectar from flowers is best for the hummingbirds, but sugar water feeders won't hurt them, either. (Photo: Becky Matsubara/Wikimedia Commons)

"Although we 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," Rachel Vannette, assistant professor in the UC Davis department of entomology and nematology and co-author of the study, said in a statement. "However, a tiny fraction of those microbes has been associated with disease, so we encourage everyone who provides feeders for hummingbirds to clean their feeders on a regular basis and to avoid cleaning feeders in areas where human food is prepared."

Vannette explained that these microbes are influenced heavily by the birds' diet, but that the impact of the microbes isn't understood yet.

"We don’t know what the consequences are for bird health or gastrointestinal flora," she said, "but we think that there should be more studies examining this, as many, many people use feeders, and the birds are opportunistic and drink from feeders."

Vannette and her fellow researchers published their findings in the Proceedings of the Royal Society B.

If you have hummingbird feeders, keep them clean. If you'd rather rely on the natural habitat instead, grow plants that hummingbirds like. We have recommendations for both of those scenarios. In What hummingbirds want, MNN's Tom Oder explains everything from how and where to set up feeders properly to what kinds of plants to grow and more.

Are hummingbird feeders safe for the birds?
A study led by the University of California, Davis, found that hummingbird feeders aren't vectors for harmful pathogens, but they do need cleaning.