Humans can’t hear the difference between male and female cardinals, but the birds themselves sure can. When Columbia University researcher Ayako Yamaguchi played recordings of male cardinals in a thick area of brush other male cardinals attached the shrubs. When female voices were played, other female cardinals answered the song.
Then the big question was why? Although this was discovered in 1998, I just recently became interested in the question of cardinal voices because I had been given some misinformation. I had always thought that cardinals, in addition to their monotonous whistle, “sweet, sweet, sweet,” also had a two pitched song that sounded like “teacher, teacher, teacher.” Now this is where I got confused. That is also the phrase that is ascribed to the ovenbird. I was pretty sure that I had seen cardinals singing this phrase, but a person who should know a lot more about wildlife than I do said that the “teacher” phrase was always the ovenbird.
Today, I know that I was right. I watched and listened to a female cardinal singing “teacher, teacher, teacher.” Perhaps I should say she was singing “wheeta, wheeta, wheeta.” That sent me hunting for audio files of the two species. I found some at Bird Songs of the Great Lakes. You can listen to snippets for free, or buy single files, or the entire CD. The samples were enough to confirm that the two birds sound very similar. The cardinal has two very definite syllables in this phrase. The ovenbird has a much stronger emphasis on the first syllable. I’m not sure that I’m good enough at listening to tell the difference in the woods. But at least I have more information now.
So back to the question of male and female cardinal song. It seems that once Yamaguchi had proved that the birds could tell the gender difference by song she set about to analyze why. It turns out that the females have more overtones in the sounds they make, while mature male voices are more pure. And, interestingly enough, the chemical reason is the same as the reason that human males have deeper voices than females- testosterone. She theorized that the testosterone thickened the vocal cords in the birds’ syrinx, the avian equivalent of the larynx, or voicebox, in humans.
One reason that cardinals are interesting to study is that both sexes sing. This is quite unusual in northern birds, although it is more often encountered in tropical species. There is some application to the study of how humans acquire speech. Cardinal chicks go through a babbling phase, and then proceed to the rougher voice which the female retains. As the male juveniles begin to produce androgens (the male hormones) their voices become more clear. This clarity can only be perceived by humans through electronic analysis of the sound. But the birds can tell!
One study proposed that males learned to sing from their fathers, and females from their mothers. This theory was proved incorrect when captive birds were purposely exposed to recordings of song from only the opposite sex adults. Both genders of chicks began with the songs containing overtones, but as the males matured their notes became pure, proving that the cause was something innate to the gender, not acquired through their environment or learning.
More bird calls at all-birds.com
Read Cardinals Can Recognize Gender By Song, Columbia University Biologist Finds
