Many male birds in the Galloanserae clade, which includes pheasants, peacocks, and swans, attract mates with their vibrant feathers—the more colorful the feathers, the more appealing the birds appear to potential mates. But it turns out flashier feathers don't necessarily mean birds possess better genes. 

Evolutionary biologist Judith Mank told National Geographic, “There have been lots of theories that the ornaments, the beautiful colors and big tails, are sported by the most fit males.” However, Mank and several colleagues recently analyzed genetic materials from both “drab” and “flashy” birds, and found that the flashier birds actually had mild gene mutations that could be harmful to offspring in the long run. The so-called "drab" birds, meanwhile, lacked the mutation, according to the study.

This means that, for years, birds and scientists alike have been making an incorrect assumption—that more beautiful feathers are a sign of better genes. It’s true that flashier birds are more likely to attract mates, and pass down their genes. But, as Mank explains, there’s ultimately no connection between flashiness and genetic fitness: “A male may be attractive, but he doesn’t deliver at the genetic level. In a way, it’s false advertising.”

[h/t National Geographic]