G'day again,I probably should have explained that the Australian Swan, cygnus atratus has black plumage, not white, so Harrington is simply writing about experience, not what might seem to be a fantasy to non-antipodeans.
Although Western Australia has adopted the Black Swan as its state avian emblem, they are found all over Australia and were first seen by Abel Tasman in Tasmania right at the bottom of the east, where they are commemorated by the town names Cygnet (nice folk/world music festival in mid January - high summer, locally) and Swanport (on the Swan River, of course).
Harrington's reference to them flying westward at sunset suggests he is on the east coast, as they fly inland to sheltered waterways for overnight rest.
Regards,
Bob Bolton