In their tropical expeditions, European biologists Charles Darwin, Alexander von Humboldt and Alfred Russel Wallace described the very colorful richness of flora and fauna compared to the species of northern latitudes.

As you get closer to the tropics, the variety of structures, the beauty of the forms and the mixture of colors increase.marveled at the German naturalist Humboldt (1769-1859), who dramatically explored the Amazon forest.

Since then, some scientists have suspected the existence of a sort of geographical coloring pattern of the species, which varies according to latitude, but have not been able to provide proof.

To confirm the hypothesis, biologists from the British University of Sheffield studied more than 4,500 species of passerines, the largest family of songbirds (swallows, magpies, larks, nightingales, blackbirds, chickadee, paradise tanagers … .), well distributed worldwide.

They filtered the feathers of adult specimens (male and female) from the collections of the Natural History Museum in Tring, England: each was photographed on a black background, from three different angles, with and no UV filter.

Thanks to an in-depth method of analysis (one of the fields of artificial intelligence), they obtained from these photo sessions 1500 pixels per plumage. On this basis, they were able to measure a rate color of each species, then compare it to the location of the bird, with a scoring system.

The results confirmed that the closer you are to the equator, the brighter the colors, and they fade as you move away from it. A kind of biogeographic guidelinesgenerally valid for both sexes, despite slight differences.

What is the reason? Several explanations have been presented, including that of Alfred Russel Wallace, who saw in the lush vegetation of tropical forests a natural camouflage that allows the bright colors of birds to thrive throughout the year, when their companions in temperate forests need to adapt. their feathers on bare winter trees.

A prediction confirmed by the study. We found that color was higher in birds in dense habitats, such as rainforests, Christopher Cooney told AFP. Another factor presented: food, because birds that eat fruit and nectar, which are more present in tropical latitudes, have a darker color, he added.

His research also establishes a correlation between species diversity and different colors, suggesting that this may be beneficial for birds. to better identify themselves with each other in an environment full of species.