If You See Mold on Your Hummingbird Feeder, This Is What to Do

There may be no sweeter sight than watching a tiny, iridescent hummingbird feast on sugar water at your backyard feeder. If there’s mold on your hummingbird feeder, though, you might unknowingly harm the very birds you’re trying to attract. Here’s how to recognize whether you have a mold problem — and how to fix it.

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What Mold on a Hummingbird Feeder Looks Like

Irenesidoti1 — Courtesy Irene Sidoti
If you see black or green buildup, empty the feeder and clean it immediately.

Mold in hummingbird feeders is usually black, green, or gray. It frequently shows up as little dots or slimy residue, although it can float in the nectar itself. You might also spot it around the feeding ports and along any grooves or seams. This buildup usually won’t rinse away easily; it’ll require some careful attention and extra work to keep it in check. Have questions about feeding hummingbirds? Check out our expert-approved hummingbird feeding FAQ!

What Causes Mold to Form in Hummingbird Feeders?

stop hummingbird feeder from leaking — Courtesy Mariah Wilder
There doesn’t appear to be mold on this feeder, but it’s a good idea to know what to look for.

Molds of all kinds love warm, damp environments. Hummingbird feeders are full of sugar water, which provides an excellent environment for certain types of mold to grow. Since hummingbirds are summer visitors in most places, warm weather, crevices in the feeders, and the presence of sugar water combine to provide perfect conditions for mold.

When weather gets hot, mold grows even faster — especially in feeders hung in sunny spots. Hummingbird feeder mold can appear in just a day or two, especially in warm conditions. The longer sugar water remains in a feeder, the more likely it is to show up.

Never add these foods to your hummingbird sugar water.

Can Mold Make Hummingbirds Sick?

hummingbird photos — Courtesy Vanessa Woodlock
The photographer of this image noted that this hummingbird’s tongue appeared for only a second — but a dirty hummingbird feeder might mean the bird would be unable to retract it.

Unfortunately, it can. Mold causes candidiasis, a fungal infection that affects a hummingbird’s tongue. Candidiasis causes the bird’s tongue to swell. If the swelling becomes severe enough, the bird might be unable to retract it. Affected birds become unable to feed, and they can starve to death.

How to Clean Mold on Hummingbird Feeders

If you notice mold on your feeder, take it down immediately. Empty out the spoiled nectar — and preferably down a drain rather than outside, where the mold can harm other animals or birds. For your safety, clean your sink well afterwards. Take your feeder apart completely, including any removable ports. Rinse or wipe off visible residue.

From there, there are several ways to thoroughly deep-clean your feeder:

Scrub your feeder with hot water and mild dish soap, using small brushes to get into tiny crevices, holes, and grooves.
Make a bleach solution from 1 part bleach to 9 parts water, or a vinegar solution from 1 part vinegar to 2 parts water. Soak the feeder parts for about an hour, then scrub out all crevices, holes and grooves.
Run your feeder through the dishwasher. Before taking this step, check the instructions for your specific feeder to ensure it can be safely placed in the dishwasher.

Rinse your feeder thoroughly to remove soap, vinegar, or bleach residue, which can also make birds sick. Once it’s completely dry, check it over one last time to check for any stubborn mold you might have missed.

Check out the best ways to clean your birdbath.

How to Prevent Mold on Hummingbird Feeders

feeding hummingbirds — Courtesy Kimberle Glidden
Make sure you’re keeping your feeders clean and providing fresh sugar water.

Mold can be hard to get rid of once it appears, so it’s better to prevent it. Try these tips to avoid mold in hummingbird feeders:

Clean feeders regularly. This means cleaning them at least once a week in cooler weather (early spring and late fall) and twice a week when it’s warmer. When temps surpass 90°F, you should clean your feeder daily.
Keep your nectar fresh by replacing it every two to three days. You can make your sugar water in advance and keep it in the fridge to make this process quick and easy. If birds aren’t emptying your feeder quickly, consider buying a smaller feeder.
Hang feeders in shaded locations to slow fermentation and mold growth. Protecting feeders and nectar from the hot afternoon sun can be especially helpful.

Here’s what to do if your hummingbird feeder is leaking.

What Does It Mean If Hummingbird Nectar Is Cloudy?

Cloudy nectar is spoiled nectar. Sugar water ferments quickly in warm weather, which makes it unsafe for birds. If you notice cloudy nectar in your hummingbird feeder, empty and clean it, then fill it with a fresh batch of homemade nectar.

There are several reasons to avoid using red dye in sugar water for hummingbirds. One reason is that the red coloring may make it harder to see when the solution turns cloudy, or when mold begins to form.

Sources

VCA Animal Hospitals, “Candida Infections in Birds“
National Audubon Society, “Hummingbird Feeding FAQs“
Vox, “You Might Accidentally Be Killing Hummingbirds“

Author

Jill Staake

During the 14 years she's written for Birds & Blooms, Jill Staake has relied on the expertise gained during her time as Assistant Curator of outdoor exhibits at the Museum of Science & Industry, Tampa. There, she helped grow gardens full of host and nectar plants for more than 20 species of native butterflies, raised from caterpillars to sh...

Reviewer

Kenn and Kimberly Kaufman

As a teenager in the 1970s, Kenn Kaufman hitch-hiked all over North America in pursuit of birds, an adventure later chronicled in his cult-classic book Kingbird Highway. After several years as a professional nature tour leader, taking groups to all seven continents, he transitioned to a career as a writer, editor, and illustrator. His 14 books incl...