Testosterone Injections Help Male Birds Sing Better, Woo Mate

The discovery that injecting testosterone in areas of the male canary's brain affects its ability to attract a mate through singing could help explain the effects of human steroid use on sexual behavior, according to researchers at Johns Hopkins University.

Published in the journal Proceedings of the National Academy of Sciences, the study revealed how introducing testosterone to a specific area in male canaries' brains caused the frequency - but not the quality - of their song to increase.

Hormones like testosterone play a key role in coordinating areas of birds' brains to create physiological responses like birdsong. In order to better understand exactly how the hormone affects a male bird's singing, the researchers divided 20 canaries into two groups. One received a testosterone injection in a part of the brain called the medial preoptic nucleus (POM), which controls sexual motivation, while the other received an injection that acted throughout the brain. A third received no treatment.

According to graduate student and lead author Beau Alward, those birds whose POM was treated sang at high rates, but were unable to sing at the quality most attractive to females. In contrast, the canaries that received testosterone throughout their brains experienced an increase in song quality - a finding consistent with the belief that the hormone works on different parts of the brain to regulate birdsong.

"Our data suggests that testosterone needs to act in different areas of the brain to regulate the specific components of this complex social phenomenon," Alward said.

"It appears that, like in so many other species, testosterone in the POM can regulate an animal's motivation, in this case, the motivation to sing," he added. "However, singing and courting a female is more than just motivation. There is the quality of the song that is required to successfully attract a mate and then the process of attending to the female, or singing to her, when she is there which requires the coordination of multiple brain regions."

Because the hormones studied are the same as those found in humans, the researchers argue the implications go far beyond canaries, offering insight into how steroid use in humans affects sexual behaviors.