What season is the scenery written by Wang Wei in Bird Watching Creek?

Wang Wei's Birding Creek describes the scenery of this season in autumn. The whole poem is as follows: In the Tang Dynasty, birds were singing in the brook, osmanthus flowers fell leisurely, and the mountains were empty at night when spring came. When the moon comes out, birds are singing in the spring stream. Autumn night is silent, and osmanthus falls unconsciously. Silence makes the mountains in autumn night feel more. ...