The amazing eye of a hummingbird is able to distinguish colors that people do not see. New studies show that the visual apparatus of these birds has a special additional cone that a person does not possess. The ability to distinguish non-spectral colors helps that bird species in their behavior, reproduction, feeding and salvation from predators. Unlike the human beings who have three components in the visual organ, birds have four of them and all of them help to perceive a trichromatic color.
It consists of mixing different colors, namely a mixture of red, green and blue. Due to that factor, the human brain perceives, for example, the violet color as homogeneous, and not as a mixture of red and blue.
But in hummingbirds, their additional component gives a greater number of spectral waves and they see colors that are inaccessible to the human eye. Mary Caswell Stoddard of Princeton University says that people are color blind compared to hummingbirds and some other bird species.
The fourth component of the color cone expands visual capabilities to ultraviolet light, which allows birds to perceive a combination of ultraviolet colors. The scientists decided to verify that fact and conducted an experiment by creating a model of LED tubes "bird's eye".
All of them are programmed to display a number of colors, including non-spectral ones. Then these devices were placed next to drinking bowls with water. Some bowls had sweet water that birds liked. Another bowls had a simple water.
Then the bowls were swapped and the scientists observed whether birds could use a color indicator to determine where the tasty water was. In a series of experiments over the course of three years, it turned out that the birds distinguish excellently both colors and color shades, preferring sweet water to simple.