News Animals Hummingbirds Are Able to Smell Danger Vultures aren't the only birds who recognize odors, study finds. By Mary Jo DiLonardo Mary Jo DiLonardo LinkedIn Twitter Senior Writer University of Cincinnati Mary Jo DiLonardo has worked in print, online, and broadcast journalism for 25 years and covers nature, health, science, and animals. Learn about our editorial process Updated September 9, 2021 01:06PM EDT Fact checked by Haley Mast Fact checked by Haley Mast LinkedIn Harvard University Extension School Haley Mast is a freelance writer, fact-checker, and small organic farmer in the Columbia River Gorge. She enjoys gardening, reporting on environmental topics, and spending her time outside snowboarding or foraging. Topics of expertise and interest include agriculture, conservation, ecology, and climate science. Learn about our fact checking process Share Twitter Pinterest Email Tongho58 / Getty Images News Environment Business & Policy Science Animals Home & Design Current Events Treehugger Voices News Archive Glittery and graceful, hummingbirds hover and flit in midair as they gather nectar. But it’s not just their athleticism that helps them source food. New research finds that these tiny birds have a great sense of smell that helps them detect potential danger when they are hunting for nectar. “In the last 10-15 years, researchers have just now begun to realize the importance of smell in birds in general. For a very long time, it has been known that some birds, such as vultures, have a keen sense of smell and use it to find food,” study co-author Erin Wilson Rankin, an associate entomology professor at the University of California Riverside, tells Treehugger. “However, the role of olfaction in most birds has only been recently recognized. That may be in part because many birds do not appear to use odor to help them locate food.” In earlier studies, researchers were unable to show that hummingbirds preferred the smell of flowers that contained nectar. Also, flowers that have been pollinated by birds don’t have strong aromas, like those that have been pollinated by insects. That’s why scientists didn’t believe that birds had the ability to smell odors. But with this new study, researchers believe otherwise. For their experiment, Rankin and her colleagues observed more than 100 hummingbirds in the wild and in aviaries. The birds were given the choice between feeders that contained just sugar water, or sugar water with the addition of one of several chemicals with a scent that meant there was an insect present. The feeders otherwise looked exactly the same. The scents included one deposited on flowers by European honeybees, a chemical produced by Argentine ants, and formic acid, which is released defensively by some formica ants and can injure birds and mammals. “If a bird has any exposed skin on their legs, formic acid can hurt, and if they get it in their eyes, it isn’t pleasant,” Rankin said in a statement. “It’s also extremely volatile.” In the experiments, the hummingbirds avoided the feeders with the sugar water that contained the ant-derived chemicals. They didn’t react to the sugar water with the honeybee scent, even though it’s been known to keep other bees from visiting flowers. To make sure the bees weren’t avoiding the feeders due to a fear of a new smell, the researchers performed an extra test with sugar water and ethyl butyrate, which is a common additive in human food. “It smells like Juicy Fruit gum, which is not a smell known in nature,” Rankin said. “I did not enjoy it. The birds did not care about it though and didn’t go out of their way to avoid it.” The results were published in the journal Behavioral Ecology and Sociobiology. Avoiding Danger For hummingbirds, recognizing smells isn’t just about finding a meal. They use their sense of smell much differently than vultures. These birds use the massive olfactory bulb in their brain like an “airborne bloodhound” to detect decaying carcasses. Instead, hummingbirds use their excellent vision to locate flowers from which they collect nectar. “Flowers, while specific species may be patchy in distribution, are much more common and numerous than the animal carcasses that vultures rely on. Thus, it is not surprising that vultures use their sense of smell to find carcasses which they then scavenge,” Rankin explains. Hummingbirds use their ability to smell in a different way. “Rather than using odors to find flowers, they will avoid flowers or feeders that have specific insect odors on them, such as formic acid or an Argentine ant aggregation pheromone. A hummingbird can use the chemical cues associated with ants to help them determine if the hummingbird should feed from there, or avoid it because it's already occupied by ants, which can drink the nectar first or potentially harm them,” Rankin says. “Ants are also very hard for hummingbirds to see until they are up close, so being able to smell them even when they are hidden deep in a flower could be advantageous. By avoiding defensive chemicals, hummingbirds can avoid interactions with ants and focus on feeding at safer food resources.” View Article Sources Kim, Ashley Y., et al. "What is That Smell? Hummingbirds Avoid Foraging on Resources with Defensive Insect Compounds." Behavioral Ecology and Sociobiology, vol. 75, no. 9, 2021, doi:10.1007/s00265-021-03067-4 Bernstein. Jules. "Hummingbirds Can Smell Their Way Out of Danger." University of California, Riverside, 2021. study coauthor Erin Wilson Rankin, an associate entomology professor at the University of California Riverside Barrat, John. "Scientists in Awe of Huge Olfactory Bulb Found in Turkey Vulture Brain." Smithsonian, 2017.