For the male canary, the ability to sing a pitch-perfect song is critical to wooing female canaries. As the seasons change, so does song quality and frequency. The hormone testosterone plays a role in this changing song behavior.
Researchers at The Johns Hopkins University have found that introducing testosterone in select areas of a male canary's brain can affect its ability to successfully attract and mate with a female through birdsong. They also found that enhancing song activity based on testosterone in one brain area can change the size of a separate brain area that regulates song quality. These findings could shed light on how testosterone acts in the human brain to regulate speech or help explain how anabolic steroids affect human behaviors.
In a paper recently published in the journal Proceedings of the National Academy of Sciences, graduate student and lead author Beau Alward along with senior author Gregory F. Ball, vice dean for science and research infrastructure and professor in the Department of Psychological and Brain Sciences in the Zanvyl Krieger School of Arts and Sciences, found that when male canaries received testosterone in a specific area in the brain, the frequency of the song increased. However, the quality of songs sung did not change in comparison to the male birds that received testosterone throughout the brain.
Hormones such as testosterone coordinate several areas of the avian brain to produce a physiological response, such as birdsong, said Alward. To determine how testosterone influences birdsong, Alward and Ball divided 20 canaries into two groups to receive a hormone implant.
One group received the testosterone injection in a specific area of the brain, the medial preoptic nucleus, or POM, which controls sexual motivation in many animals as well as in humans. The second group was received with testosterone that acted throughout the brain. A third group received no hormone treatment at all.
Alward said both groups of birds that received testosterone treatment sang but the researchers noticed in some cases the canaries' songs were sung poorly. The birds that only received testosterone to the POM sang at high rates, but could not produce high quality song that is most attractive to females.