The flutelike songs of the male hermit thrush (Catharus guttatus) are some of the most beautiful in the animal kingdom. Now, researchers have found that these melodies employ the same mathematical principles that underlie many Western and non-Western musical scales—the first time this has been seen in any animal outside humans. The scientists analyzed the spectrograms (barcodelike representations of the frequencies in a sound) of 71 songs containing 10 or more notes made by 14 of the birds; the songs were collected across North America over more than 50 years by various individuals. Their statistical models showed that 57 of these songs closely resembled what musicians term a harmonic series—that is, the pitches of the notes follow a mathematical distribution known as integer multiples. Human musical scales are governed by these same mathematical constraints. It’s doubtful that the similarity is due to the physics of the birds’ vocal tract, the team reports online today in the Proceedings of the National Academy of Sciences. Rather, it seems male hermit thrushes choose to sing notes from these harmonic series. It may be that such notes are easier for the males to remember, or provide a ready yardstick for their chief critics—female hermit thrushes. The study adds to other research indicating that human music is not solely governed by cultural practices, but is also at least partially determined by biology.