Why do birds sing in the morning? It’s the triumphant shout: “We got through another night!”

Enid Bagnold (1889-1981) English writer

(Attributed)

Unsourced in this form.  In her 1969 autobiography she writes:

I hear that waking before dawn, that sentinel cry; and in thicket and thorn up comes the music. I hear it in the pillow; it intoxicates me. Why do they do it? I have never been taught about birds. Is it the triumph-shout -- "We have got through another night!" It may be.