Birds are more colorful near the equator

Whether the father of The Origin of Species Charles Darwin, German explorer Alexander von Humboldt and British biologist Alfred Russel Wallace were all dazzled by the vivid colors of the flora and fauna during their tropical expeditions in the 1800s, especially compared to what they used to see in northern Europe.

Now, reports the site Phys, a study published on April 4 in the journal Nature Ecology and Evolution “confirms the theory of Darwin and others that the closer birds are to the equator, the more vivid colors they have, and the farther away they become, the duller they become”.

To reach these conclusions, the researchers studied more than 4,500 passerine species from around the world, specimens of which are particularly well preserved at the Tring Natural History Museum in the United Kingdom. They took pictures from different angles, in visible light and in ultraviolet light, of the birds’ plumage. Then, “Using deep learning – an artificial intelligence technique – to extract data from image pixels, they identified the color of 1,500 different parts of each bird’s plumage,” describe Phys.

Size, climate, diet and sexual character

From there, the scientists categorized the birds based on their color and compared them based on their geographic origin. Result, reveals the Swiss site The weather :

“There is indeed a color gradient related to latitude.”

Scientists have also highlighted other factors related to color, such as size, climate or diet. The smaller a bird is or the smaller it is in a warm and humid environment, the more colorful its plumage will be. Finally, the dissimilarity between male and female seems to play a particularly important role.

“It is the female who chooses the male”, explains to the Swiss daily Iliana Medina Guzman, evolutionary biologist at the University of Melbourne, Australia, who did not participate in this work. “The more competition there is between the males, the more colorful these are.”

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