Many birds have beautiful calls, and some -- like the North American hermit thrush -- produce something that sounds an awful lot like human music. Just listen to the video above: When the bird's song is slowed down, it sounds remarkably like human compositions for the flute. Since the early 20th century, ornithological studies have claimed that the hermit thrush actually follows the same melodic rules that humans do. But for the first time, researchers have produced proof. According to a study published Tuesday in the Proceedings of the National Academy of Sciences, these birds select notes that are related by the same simple mathematical ratios that humans use to create harmony. From Motherboard:

Music is simpler than most band class teachers would have us believe. Every sort of musical scale, Western and non-Western, is harmonic. What that means is every note, or acoustic frequency, is a whole number multiple of some base note (or frequency). So, if you have some note x, the next highest note is simply 2x. The next highest after that: 3x. And so forth.

When the researchers analyzed 71 different songs produced by the hermit thrush, they found that most of them (57) used the same musical math that we do. It's possible that female hermit thrushes pick their mates based on their ability to sing according to these scales. It's also possible that they (like humans) find it easier to remember melodies made by these rules, and build their songs around them so they're easier to learn and recognize. We don't know that there's something inherently pleasing about this way of creating music -- in fact, previous studies on other species of musical birds have failed to find evidence of this harmonic similarity to humans. Just because they follow our rules doesn't mean that hermit thrushes are doing so consciously, so we might not actually be singing the same tunes.