Here's a short poem by Christina Rossetti. A dirge that references the end of summer "when lithe swallows muster for their far off flying from summer dying..."
Summer won't be dying here for several more weeks, but some of the "lithe swallows" are already gathering. Purple Martins, for example. They are among the earliest of our summer birds to arrive, in late January or early February, and the earliest to leave, often in early July.
Last week, though, I still heard some late-goers flying about in my neighborhood, gathering for their long journey south, reluctant, perhaps, to say a final good-bye to summer's abundance.