There is a bird in the poplars!
It is the sun!
The leaves are little yellow fish
swimming in the river.
The bird skims above them,
day is on his wings.
It is he that is making
the great gleam among the poplars!
It is his singing
outshines the noise
of leaves clashing in the wind.
- William Carlos Williams
Yes, another poem by the same poet under the same title. Strange but true. For more by Williams, check out Sour Grapes. Public domain.
Throughout this poem, Williams has created a sense of urgency, of fun. Exclamation marks are used frequently for its shortness, and the extended metaphor of the bird works well, effectively linking images in the reader's mind. Another metaphor concerns leaves, turning them into little yellow fish, something which is easy to imagine, given their flitting, indecisive nature.
"Phoebus", of course, refers to the classical god of the sun (ie, Apollo), and links the bird in the sky to the sun. The final lines are somewhat obscure, in the tradition of Williams: "It is his singing/outshines the noise/of leaves clashing in the wind." Singing outshining noise? An abstract concept, perhaps, but one that works well - an intensity of light from a radiant being that renders all else duller.