That Really Hums: How Hummingbirds Can Avoid Predators By Smelling Them

Hummingbirds can catch a whiff of danger in a split second, allowing the hovering nectar addicts to dart to safety before being attacked, a study has found

Researchers from the University of California-Riverside found that despite what was previously thought, hummingbirds have a keen sense of smell which they use to sniff out potential threats.  The study was published in the journal Behavioral Ecology and Sociobiology on Sept. 3.

“This is pretty exciting, as it is the first clear demonstration of hummingbirds using their sense of smell alone to make foraging decisions and avoid contact with potentially dangerous insects at a flower or feeder,” said Erin Wilson Rankin, associate entomology professor and study co-author.

The 100 hummingbirds used in the study were given the choice of feeding at two feeders, one of which contained sugar or sugar water and one that contained formic acid, which is carried by ants that are known to harm hummingbirds.

“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.

The hummingbirds in the study avoided the feeders that contained the formic acid and chose the feeders with the sugar and water.

The researchers wanted to ensure that the birds weren’t simply avoiding the formic acid because it was a new smell, so they set up the experiment using ethyl butyrate, a common additive in human food, instead of the acid.

“It smells like Juicy Fruit gum, which is not a smell known in nature,” Rankin said. “The birds did not enjoy it. But they did not care about it and didn’t go out of their way to avoid it.”

The researchers believe that the study raises new questions about the underrated importance that scent plays in birds’ foraging decisions and specifically, hummingbird foraging.

“Hummingbirds and insects might be competing for floral resources,” Rankin said. “Their foraging decisions help us understand how the ecosystem functions, and any actions that ultimately might be needed for conservation.”

There are almost 340 species of hummingbirds, and all are found solely in the Americas, ranging from Argentina’s Tierra Del Fuego to southern Alaska, according to the Smithsonian’s National Zoo and Conservation Biology Institute.

Hummingbirds’ saber-like wings beat about 70 times per second in direct flight, and more than 200 times per second while diving, the institute said.

Edited by Judith Isacoff and Matthew B. Hall