"A long, dark, endless ribbon" of migrating birds in time dwindles to less than a hundred because townspeople who disliked their noise and germs set about to be rid of them.
In lyrical language filled with sensory images, a father describes to his son his experience as a young boy watching the migration of "a long, dark, endless ribbon" of birds (probably starlings and grackles). He explains that the townspeople, who complained about the noise and germs, scattered bitter seed (poison) to feed the birds and the vast numbers were diminished to tiny hurried flocks. He is still hoping that they might see "the Black Sky River flow again".
I miss the mystery, the wondering of things without beginning, without end.
The lovely oil paintings enhance the melancholy mood of the story.