How a naughty bird cheats with fancy feather structures

In some ways, having the excess energy to develop and maintain these feathers could actually turn out to be a honest signal. It takes protein to build them, and the bird needs to produce oils to keep them in good shape. They also require constant pruning. So if it turns out that parasites attach themselves to these microstructures more easily, it could mean that a man would even need to spend After energy grooming. “The fact that you have this time, that you have these oils, and that you had the pen in the first place, all of these could be honest signals,” Dumbacher says. Basically: Not only am I as dapper as I claim in my dating profile, but I’m parasite-free as well. Which, swoon.

But why bother to evolve elaborate feather microstructures when males already have the pigmentation to signal females? Well, that’s the literal beauty of evolution. “The evolution is quite remarkable,” says Shultz. “Men will likely find a way to develop a way around the signal to make themselves appear brighter, more elaborate, or more whimsical, without necessarily putting in the same cost. And so these males will have more mates, they will be healthier, so they will probably have more offspring. And so, thanks to natural selection, this trait will take over. “

In other words, female tanagers don’t want a scrub. If a brightly colored man is most likely to be the healthiest, evolutionarily, she wants to give him those genes. clean son. If her sons do not appear, they do not reproduce, while someone else’s more showy children continue their own genetic lineage. It’s kind of an evolving arms race. Women want the fittest men, but men are trying to play with the system. Instead of spending time and energy stuffing himself with more fruit carotenoids, the male can “cheat” using the microstructures of his feathers. Shultz and his colleagues call it the “proxy treadmill,” in which men develop tricks to signal their fitness without necessarily getting fitter.

“There’s this treadmill of these constantly changing proxies,” says Shultz. “Men and women are in this war against men who are trying to do the best they can while investing as few resources as possible, while women want to use traits that will actually be indicative of the underlying quality of their work. ‘a man. A woman cannot simply give up her preference for more showy men, as this will doom her sons to be unattractive.

It is possible that this preference for flashy males has started to evolve in tanagers as they already look for bright colors when foraging: these birds indicate the presence of delicious fruit. “If a male has a really bright red and females are already turning their heads towards that color, then that’s going to give him an advantage,” Dumbacher says. “Vertebrates develop an aesthetic sense. There are different reasons that women may prefer something. And as long as there isn’t a huge cost to liking it, it can change just because women love it.

Evolutionary biologists call this a “shift to the right.” Or at least they should.

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