The tiny humming-bird to hover, those who come to drink the nectar of the flowers, flapping its wings so quickly that they are barely noticeable, have another secret. They can distinguish between a world that’s invisible to us.
A recent study shows that these hummingbirds use their ability to see in the ultraviolet for food, reports the New York Times. An ability that also serves as their breeding.
From the point of view of the bird, many plants, and even feathers are of a rich colour that is invisible to the human eye. They live in a world more colorful than ours, the researchers found the Rocky Mountain Biological Laboratory, which tested 19 pairs of colors. Their study was published in the Proceedings of the National Academy of Sciences.
The perception of color, among them as among us, is based on photoreceptor cells (or cones) in the retina of the eye, are dedicated to the detection of color — each responding to different wavelengths of light. For example, when the light is reflected on an apple, a leaf or a field of daffodils, this sends signals that the brain generates the perception of red, green, or yellow.
Humans have three types of photoreceptor cells. Most birds have four, one of which is sensitive to ultraviolet light : it is said that they are tétrachromates, such as most reptiles, amphibians and like some fish.
Researchers have long known that colors UV are widespread in the animal world. But the hummingbird, and, more broadly, the birds, are not among the most generously endowed of this type of cell : the shrimp-mantis, or squille of the Great barrier reef, in Australia, would have 12 ” cones ; which, surprisingly, does not give a vision more subtle colors.
The authors of the new research, led by biologist Mary Caswell Stoddard, of Princeton University, have spent three summers in a mountain meadow in Colorado, to observe hundreds of hummingbirds and attempt to determine how these birds use colors UV in their daily lives. In particular, researchers planted in the nature of a small structure with two tripods, each crowned with a saucer filled with liquid and a light colored.
These lights seemed to be identical to the human eye, but one of the two was incorporated, in addition to the lights, ” visible “, UV light.
The researchers have received nearly 6,000 visits of hummingbirds who come to taste the nectar. By changing the positions of the tripods, it quickly became evident that the hummingbirds were beautiful and well the difference.
At the same time, experiments with thousands of samples of feathers and plants reveal that the pairs of colors are not all easy to differentiate for all the birds. The researchers suspect a link with the colors that are more present in their environment. The week, for example, hatching of the flowers of Gilia scarlet, the hummingbirds that distinguish more particularly the red color could better enjoy their nectar.