Hummingbirds See Tons Of Colors Invisible To The Human Eye

Hummingbirds make decisions on a variety of topics based on the colors they see, with many of such hues invisible to human eyes. A new study concluded that the flying jewels could see a range of non-spectral colors or hues emitted by largely distinct sections of the color spectrum. Humans, on the other hand, can see only one non-spectral color, and that is purple.

A Fourth Cone

The human eye can detect purple color when the long-wave red and short-wave blue cones in the eyes are stimulated. However, human eyes are unable to detect the third green medium-wave cone. The hummingbird has a fourth cone that allows them to detect ultraviolet light. This four-color cone vision is known as tetrachromatic. Recently, researchers studied the reaction of wild broad-tailed hummingbirds to these colors.

According to Mary Caswell Stoddard, while biologists have long believed that birds can see a series of diverse non-spectral colors, the results of their study confirmed this is really true in the case of hummingbirds. Dr. Stoddard is an assistant professor in the Princeton University department of ecology and evolutionary biology and is the lead author of the study. “Our results are consistent with the idea that birds have tetrachromatic (four color cone) vision and can see a vast range of colors we humans can only imagine,” she wrote in an email.

Special Gears

The study was published Monday in the Proceedings of the National Academy of Sciences journal. Researchers conducted their experiment at the Rocky Mountain Biological Laboratory located in Gothic, Colorado. They set up outdoor gears for their experiments and trained some hummingbirds to use them. They used hummingbirds that prefer to breed at high-altitude alpine meadows. Researchers performed the experiments during summertime for three years.

The scientists used a custom LED device that shows two distinct colors on circular platforms next to two hummingbird feeders. One of the feeders contains a reward such as sugar water, while the other is filled with plain water. Researchers would change the positions of the LED devices regularly so the flying jewels would not be able to relate a color with a particular reward. In a matter of hours, the birds learned which of the colors are associated with a reward. “Hummingbirds are smart, inquisitive birds — they learned new color associations very quickly,” Stoddard said.