The bird is a creature that has a very special feeling of trust in the external world, as if she knew that she is one with its deepest mystery. That is why she sings in it as if she were singing within her own depths; that is why we so easily receive a birdcall into our own depths; we seem to be translating it without residue into our emotion; indeed, it can for a moment turn the whole world into inner space, because we feel that the bird does not distinguish between her heart and the world’s.

(Rilke to Lou Andreas-Salome, February 1914)