"Spring" is a poem by William Shakespeare that documents various spring activities, but focuses on the Cuckoo birds that tell the married men how 'Cuckoo' those men are. This is a poem from the play, Love's Labour's Lost. The theme of this particular poem would be that new life mocks married life, which is a cynical view of marriage. The other various activities are all full of freshness, and they contrast starkly with the sometimes worn nature of marriage. The bird is mocking the men for their lack of newness.

Mocks married men, for thus sings he: 'Cuckoo!'

This poem is paired with another poem called "Winter." This poem also features a bird responding to various activities. In this one, the bird is an owl singing a "merry note," while the other birds, people, and objects live in a sorrowful, frozen state.

I have read a lot of Shakespeare over the years but I have never heard of a poem by Shakespeare titled "Spring." I note that nobody has tried to answer this question since it was posted on October 16, 2011. I suspect this is because nobody can identify such a poem. If there were such a poem by Shakespeare, I would guess that the theme of "Spring" would be the beauty, the delights of spring and how a young man's fancy turns to thoughts of love. Could you please clarify?