Researchers at Johns Hopkins University divided the 20 male canaries into three groups. One group was given testosterone injections in one specific area of the brain -- the medial preoptic nucleus, or POM, which affects sexual motivation.
The second group was given testosterone that acted throughout the brain and the third group was given no testosterone.
The birds that received targeted testosterone sang at a higher rate, but some sang very poorly, and the quality in others was not different from the the birds that received no testosterone. The findings are published in the Proceedings of the National Academy of Sciences.
"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. 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," said lead author Beau Alward, in a statement.
Meanwhile, the canaries who received testosterone throughout the brain displayed high-quality vocalization behavior, suggesting the hormone acts on multiple parts of the brain, which coordinate to produce a higher-quality birdsong.
The canary is considered a good model for brain study due to its adaptive neural pathways, and the researchers hope to study how testosterone acts in the human brain and how anabolic steroids may affect human sexual behaviors.