Compare the two spectrograms side by side and the results are clear: No matter how hard the diligent student tries, his replications of his own syllables are wildly variable. The zebra finch’s are nearly identical. In terms of his precision, says Mooney, “the bird is like a perfect machine.” It’s what’s known as vocal consistency, the ability to perfectly replicate the acoustic features of a song—the notes, the rhythms, the pauses—from one rendition to the next. To a bird, these subtleties make all the difference.
