Hummingbirds have a voracious appetite for nectar, the sugary fluid secreted by flowers. To survive, they usually drink between five and fourteen times their weight in nectar every day. Finding all that nectar isn’t easy. Some flowers may have already been emptied of nectar by other visitors, or might be occupied by dangerous insects such as ants.
Biologists want to understand how hummingbirds use their senses to find the right flowers to feed at. They have long known that these tiny birds can locate flowers by vision. Although vultures are known to use the sense of smell to detect the corpses of dead animals, smell didn’t seem to play a role in the foraging behavior of hummingbirds. Earlier studies, for example, found no evidence that hummingbirds could use smell to tell whether or not a flower contained nectar.
In 2021 a team of researchers from California published the first evidence that hummingbirds do use smell to avoid danger. The researchers showed that hummingbirds could detect and avoid the smell of a chemical secreted by Argentine ants to attract other ants, and the smell of a defensive chemical released by some other ant species.
The researchers allowed more than one hundred hummingbirds to choose between two feeders. One contained sugar water alone, and the other contained sugar water scented with one of the ant chemicals. The hummingbirds specifically avoided the chemicals secreted by dangerous ants, but didn’t avoid harmless smells. They ignored the scent of a common food additive not found in nature, and the smell of European honeybees. The finding helps biologists better understand how animals use their senses during the complex task of foraging for food.
