Definition of "birdsong" [birdsong]

• A musical sound made by a bird. (noun)

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• "While struggling to read a short story one afternoon, I get fixated on the word birdsong."
• "The purity of birdsong is owed in large part to rapid, controlled changes in the shape of the birds 'upper vocal tracts, according to a new study of Northern Cardinals by scientists at Indiana University Bloomington, Purdue University and Australian National University."
• "I dearly love those weeks in spring when it's cool enough to sleep with the windows open, and early enough in the year that noisy birdsong is all the alarm clock that I need."