What is the word used to describe the sound of "bird songs"?

The word used to describe the sound of bird songs is "birdsong" or "birdcall."

I'm actually referring to the actual sound that a bird song creates or makes,what is the right sound word used to describe it?

The word used to describe the sound of bird songs is "warbling."

Define warbling?

Warbling refers to the melodic and continuous singing or modulation of pitch in a quavering or vibrato manner, often produced by birds in their song. It typically involves rapidly changing pitch and volume, creating a rich and varied sound pattern.