During the past week a familiar and ethereal song has been emanating from nearby woodlands. Male Hermit Thrushes have returned, as have their flute-like songs. These songs are made with a syrinx (not a larynx like humans have), an organ unique to birds. It is not much bigger than a raindrop in most birds and is extremely efficient, using nearly all the air that passes through it. (A human creates sound using only 2% of the air exhaled through the larynx.)
The syrinx is located where the trachea splits into two bronchial tubes. In songbirds, each side of the syrinx is independently controlled, allowing birds to produce two unrelated pitches (one from each half of its syrinx) simultaneously. Hermit Thrushes can produce rising and falling notes at the same time, creating the melodious and haunting song that greets our ears early in the spring. This renowned songster can be heard at https://www.allaboutbirds.org/guide/Hermit_Thrush/sounds
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