What is the purpose of the third stanza of “auspex”

The third stanza contrasts the image of the birds from the first stanza.

Explanation:

The poem "Auspex" by James Russell Lowell tells of how the speaker's heart is like that of a songbird. Passion had left his heart just as a songbird had left it's home.

The first stanza tells of his loss of passion just like the bird leaving the home. The bird is the imagery of the lost passion or love of the poet.

Second stanza reveals his wish that if only the songbird was instead a swallow, then it would have stayed longer. And this will in turn make his love also remain longer with him.

Third stanza rejects the whole idea of the birds being a symbol of passion or love. Instead, the birds in this stanza stands as a contradiction or contrasting of the first stanza image of birds. Here, they are just a cause of "confusion' to him.