Visible Bird Song

Hugh Lofting's Dr. Dolittle, beloved by children and by parents who read to children, trained a chorus of singing birds and let the birds themselves compose the music. He and the audience noticed that the canaries sometimes went through the motions of singing although they were making no audible sound. The birds were singing ultrasonically, and if Dr. Dolittle could go to Ohio State University this week, he would see the ultrasonic bird songs that he could not hear.

Professors Donald J. Borror and Carl R. Reese borrowed an elaborate audio-spectrograph from the university's astronomical observatory (where it was used to study the scintillations of stars), and used it to analyze bird songs recorded in the fields and woods. It could hear notes much higher than the human limit (about 18,000 cycles a second), and it could catch and write down on its paper tape the fastest variations in the songs.

The visual recordings show that most birds' songs are not intended for clumsy human ears. A few of them (e.g., the songs of whippoorwills and song sparrows) can be heard complete, but others contain many parts that are too high-pitched. When heard by human ears, the golden crowned kinglet's song, for instance, must be a pale shadow of what it sounds like to another golden crowned kinglet, which can appreciate all of its highest notes.

Birds' ears must also be quicker than human ears. Some of the songs of warblers, for example, are full of musical phrases set so close together that they cannot be heard separately. Even apparently simple songs contain quick musical details that slip past human ears. On studying the visual records, the scientists found that many birds are musical gymnasts, playing on their vocal organs as if they were string quartets. The blue jay, for instance, can sing what amounts to a major chord, holding a low note and a high note simultaneously; then after a hundredth of a second, he adds a middle note. The wood thrush can hold as many as four simultaneous notes.

The scientists do not know how the birds manage these musical stunts, which are far beyond the capabilities of human singers. Their next project is to find out.

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