Who does the Swan represent in Leda and the Swan?

The bird described in the narrative is never actually identified as a swan. To fully grasp this poem, it is of tremendous help to be acquainted with some knowledge of ancient Greek mythology. Into that mythology was written the story of the conception of the woman who would become known as Helen of Troy. Unless one is familiar with the story of Zeus transforming into a swan to rape Leda, Helen’s mother, it would likely be not just impossible to determine that the swan is a symbol of Zeus but that the bird is even a swan. It gets even more complicated: swans are a favorite animal for Yeats to work into his verse as a symbol of inscrutable passion and desire.