Magic markers can change bird testosterone levels?

Yes, it’s true – well, sort of. An interesting aspect of animal sex research is that scientists sometimes manipulate animals’ bodies (such as the color or style of birds’ feathers) to learn more about how their bodies or their display of their bodies is related to sexual behavior or mating (like how male peacocks display their marvelous fan of feathers).

In a recent study reported on by the Associated Press, scientists found that when they used magic markers to darken the feathers of male barn swallows, females were differently attracted to them and the male swallows’ testosterone levels increased too. Here is an excerpt from the article:

A little strategically placed makeup quickly turns the wimpiest of male barn swallows into chick magnets, amping up their testosterone and even trimming their weight, new research shows.

It’s a "clothes make the man" lesson that – with some caveats – also applies to human males, researchers say.

Using a $5.99 marker, scientists darkened the rust-colored breast feathers of male New Jersey barn swallows, turning lighter birds to the level of those naturally darkest.

They had already found, in a test three years ago, that the marked-up males were more attractive to females and mated more often.

Read the full AP article here.

About Dr. Debby Herbenick

Dr. Debby Herbenick

Dr. Debby Herbenick is a sex researcher at Indiana University, sexual health educator at The Kinsey Institute, columnist, and author of five books about sex and love. Learn more about her work at