Siegfried Sassoon - Thrushes

Tossed on the glittering air they soar and skim,
Whose voices make the emptiness of light
A windy palace. Quavering from the brim
Of dawn, and bold with song at edge of night,
They clutch their leafy pinnacles and sing
Scornful of man, and from his toils aloof
Whose heart's a haunted woodland whispering;
Whose thoughts return on tempest-baffled wing;
Who hears the cry of God in everything,
And storms the gate of nothingness for proof.

Siegfried Sassoon

http://www.poemhunter.com/poem/thrushes-2/