According to new research published in Behavioral Ecology and Sociobiology, hummingbirds use an ill-understood sense of smell for a very practical purpose: to avoid danger.
Specifically, a research team at the University of California--Riverside found that hummingbirds use their sense of smell to detect insect and other predatorial risks near or on flowers they are hoping to collect nectar from, increasing our understanding of a key ecological concept for birds: foraging.
“Hummingbirds and insects might be competing for floral resources,” said the study’s first author “Their foraging decisions help us understand how the ecosystem functions, and any actions that ultimately might be needed for conservation.”
Researchers tagged and followed about 100 hummingbirds as they fed from two different feeders, studying which feeder the birds gravitated towards. While both feeders looked identical and contained sugar water, one feeder contained the chemical scents left behind by certain types of bees and ants, all of which can be harmful to a hummingbird. Researchers found that while hummingbirds didn’t care about the bee scents, they did avoid the ant scents. The birds specifically avoid one of the ant scents (formic acid) that can be especially dangerous for hummingbirds.
Prior to this study, it was generally believed that hummingbirds did not have a sense of smell, or that it’s role in the day-to-day activity of hummingbirds was so minuscule that it did not warrant close study. The research team reinforced this notion in their article, arguing that “avian olfaction has been considered relatively unimportant...especially in comparison to mammal or insect olfaction... hummingbirds have been assumed to not use olfaction during foraging... and comparatively little is known about the hummingbird’s ability to smell.”
Previous research on hummingbirds suggested that they instead rely primarily on vision and sound when it comes to making foraging decisions; in fact, some research suggested that hummingbirds utilize spatial memory to know which flowers they have already visited to avoid returning to flowers with no nectar, highlighting the limited role that smell has played in understanding hummingbird foraging habits.
However, a hummingbird’s olfactory nerves are still quite small, raising questions about how their sense of smell actually works. While this study suggests that researchers pay attention to hummingbird olfactory abilities, more research on the topic and its implications for ecological study is needed.