Wordsworth and Keats both wrote poems about birds, and both imbue their birds with a mystical nature, but where Keats sees the bird as a representation of a better life, Wordsworth sees it as a mysterious presence that represents the disembodied spirit of nature.
In Wordsworth’s “To the Cuckoo” he never sees his cuckoo and had long since stopped looking for it, so the bird had become a spirit that represents the rest of nature, and like the daffodils it transcends itself. In an “Ode to a Nightingale,” Keats speaks to the nightingale as the representation of his desire for happiness — Keats feels a “numbing pain” because he is so happy that the bird is happy that it begins to work on him like a drug. He sees the nightengale, at first, as the essence of summer and the chance of a new life. However, the bird eventually loses its magic beginning first as a “light winged Dryad of the trees” and slowly transforming tin a “plaintive anthem” that fades away only leaving a dejected Keats unable to see reality.
Wordsworth never loses the mysticism of the cuckoo because he doesn’t tie temporary or seasonal ideas to it, so its magic is permanent and doesn’t end. Wordsworth ties his cuckoo to nature and the “grandeurs that are found in the beating of the heart,” so a temporary loss of the bird’s song or beauty is not a reason for dejection because beauty is temporary for Wordsworth and the beauty is in the magic not the thing itself.
Keats focuses solely on the beauty of the song, so when the song is gone, he loses his beauty and is left with his own deflated self. However, his deflate is temporary because he knows the bird and beauty will return eventually. Should the cuckoo ever lose its mystery for Wordsworth, (through him finally seeing it) he would permanently be deflated.
Wordsworth’s victories and defeats are permanent, but Keats can allow for both at the same time.