How Do Hummingbirds Collect Nectar... Perceiving 'Colors Beyond the Rainbow' Invisible to Humans

Bird Eyes with One More Receptor Than Humans... Also Detect Ultraviolet Rays
Distinguish Thousands of Wildflower Colors to Collect Nectar

Birdie / Photo by Pixabay

[Asia Economy Intern Reporter Lim Juhyung] A study has revealed that hummingbirds can perceive colors invisible to the human eye.

A research team led by Professor Mary Caswell Stoddard of Princeton University announced on the 15th (local time) in a paper published in the scientific journal 'Proceedings of the National Academy of Sciences' (PNAS) that "hummingbirds can see ultraviolet light, which humans cannot perceive, through a fourth receptor."

According to the research team, the human eye has three receptors that receive light, allowing us to recognize so-called 'spectral hues' that belong to the colors of the rainbow.

However, birds' eyes have one more receptor than humans, totaling four, enabling them to see 'non-spectral hues' that do not belong to the rainbow.

To verify these findings, Professor Stoddard's team set up an experimental environment at the Rocky Mountain Biological Laboratory in Colorado, USA.

First, the team placed two feeders in an alpine meadow frequently visited by hummingbirds searching for food. One contained sugar water, and the other contained regular water.

The researchers installed LED devices emitting light on both feeders, with the LED on the sugar water feeder displaying non-spectral hues.

Birdie / Photo by Yonhap News

Over three years of experiments, hummingbirds learned that the feeder with the LED emitting non-spectral hues contained sugar water. Later, when the team displayed ultraviolet+green (a non-spectral hue) and regular green LEDs, the hummingbirds accurately distinguished the ultraviolet+green.

Additionally, hummingbirds were found to recognize various non-spectral hues such as ultraviolet+red, ultraviolet+yellow, and purple.

Professor Stoddard, who led the experiment, said, "We felt thrilled when we discovered that hummingbirds could distinguish two colors that appear identical to us. Hummingbirds are intelligent and curious, quickly learning new colors. This makes sense as they evolved to collect nectar from flowers of various colors."

According to the research team, there are 3,315 feather and plant colors in nature, of which 30% of feathers and 35% of plant colors are non-spectral hues indistinguishable by the human eye. Hummingbirds were shown to be able to distinguish each of these hues.

David Inouye, a co-author of the study and professor of biology at the University of Maryland, USA, added, "It is truly amazing to imagine how wildflowers appear to birds that can perceive colors one level beyond humans."

This content was produced with the assistance of AI translation services.