The hermit-thrush can be considered the Maria Callas of the world of birds due to extremely tuned melodies which sings, reveals a new study. Scientists have discovered that this American bird sings in the harmonic series. The human singing and the sounds emitted by musical instruments are also based on the harmonic series system, which are developed from a base note and multiple frequency higher notes from the original note. According to the study, 70% of corner of this bird follows this harmonic pattern. Robins-male hermits can sing between six to ten types of different sounds, almost always in high frequencies and a fast pace. Emily Doolittle, composer at Cornish College of Arts in Seattle, and Tecumseh Fitch, a biologist at the Univeristy of Vienna, analyzed 144 different types of songs issued by 14-male hermit thrushes. "To hear the melodies of the thrushes-hermit to a normal speed, the sounds are quite attractive, but we had no suspicion that we were going to hear a series of harmonics", indicates Emily Doolittle to the Daily Mail. To reduce the playback speed of the melodies of the birds, the harmonic series patterns became clear and it was possible to analyse the choices of notes that Robins used the melodies. About 70% of the analyzed melodies were composed by 7% and harmonic intervals included notes at random without any harmonic referential. Researchers are particularly interested in how these birds sing because the vocal tract of birds is not designed to produce specific notes within the harmonic series. One of the researchers ' hypothesis for this phenomenon might be the fact that the female song Thrush Hermit choose a male for their harmonic precision. Doolittle indicates that birds do not comprise deliberately their melodies through scales, but acknowledges that other species of birds also like the intervals used in human music.