A canary’s song sounds sweet and innocent, to us anyway. But for male birds, music is actually part of a testosterone-fueled mating ritual.
So what’s the pathway from hormone to harmonics?
It was thought that male canaries became motivated to sing when testosterone hit the specific brain region normally responsible for mating behavior. It’s called the medial preoptic nucleus, or POM.
To find out, scientists first gelded some unfortunate individuals. Some of these canaries received doses of testosterone to the POM only. Others got broad testosterone exposure throughout the brain.
After treatment, both groups of canaries began singing. Although they sang roughly the same amount, the birds receiving broad hormone doses made music that was louder and of higher quality. They also sang more while potential mates were present. The study is in the Proceedings of the National Academy of Sciences. [Beau A. Alward, Jacques Balthazart and Gregory F. Ball, Differential effects of global versus local testosterone on singing behavior and its underlying neural substrate]
So testosterone in the POM does inspire mating behavior. But the hormone must act more globally to create a proper performance. Quality courtship requires a complete bird brain.
[The above text is a transcript of this podcast.]