Photograph by Joel Sartore, National Geographic
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After studying both colorful and drab males in the avian clan Galloanserae, biologist Judith Mank concluded that “there’s no link between flashiness and fitness.”

Photograph by Joel Sartore, National Geographic

Why Flashy Male Birds Aren't Really What They Seem

Among peacocks, swans, pheasants, and other birds, males’ better looks don’t necessarily mean better genes.

As might be true in any big family, the Galloanserae clan has some gorgeous and some plain-looking members, some promiscuous and some monogamous ones.

The avian superorder includes common pheasants, peacocks, and swans among the 452 species of game and waterfowl.

But the most colorful and randy Galloanserae males may not be passing on the best genes to offspring, according to a recent study. (Read "Feathers of Seduction" in National Geographic magazine.)

“There have been lots of theories that the ornaments, the beautiful colors and big tails, are sported by the most fit males,” says evolutionary biologist Judith Mank of University College London. “We were explicitly testing that theory” in the study, published earlier this year in the Proceedings of the National Academy of Sciences.

Mank and her colleagues analyzed genetic materials from six species of birds of both dispositions. In the flashy birds they found a rapidly evolving genome marked by mild gene mutations; in the drab ones they didn’t find that. (Also see "Flashier Great Tits Produce Stronger Sperm, Bird Study Shows.")

When females mate with flashy males, genetic flaws are passed on that may affect the species’ prospects in the future.

The study confirmed that “there’s no link between flashiness and fitness,” says Mank. “A male may be attractive, but he doesn’t deliver at the genetic level. In a way, it’s false advertising.” 

The feature Basic Instincts: A genteel disquisition on love and lust in the animal kingdom appears every month in National Geographic magazine.