I’ve written about it before: a block from my house there’s a playground with a soccer field where cattle egrets forage. As the big riding lawnmower makes its rounds there, they follow it, pacing off the greenness in silent, dignified strides.

As I was picking up my newspaper this morning, I heard a loud noise, looked up from the lawn, and saw that I was abreast of a semi-trailer hauling the lawnmower away. Behind and above the trailer, flapping hard, followed one of the egrets, keeping up as best he could. For about a block more he continued, but then the truck picked up speed and left him behind.

Alone, the bird made a turn, soared to treetop level, and rose, white into white-clouded blue. I remembered what I had learned about Pavlov’s dogs and Lorenz’s geese and nature’s school where we learn motive and desire, but the white arc hinted that there may always be an unknown, somewhere in the air, to fill us with surprise and love.