The sun went down and birds flew in ellipses around three-story brick houses. The sun caught them for part of their ellipse, and made each bird shine, making the wings shine. Then they would turn gray again as they finished the arc. I stood and watched them. It was Saturday and I was going to get some badly prepared spinach pie at the St. Claire Diner.

I thought of a computer algorithm that simulates flocking behavior. I have a copy of a program that implements it, and I brought up the birds on my screen when I went home. The birds on the screen were shapes and math. The real birds were mirrors to the sky, their bright backs catching light, grabbing the sun and pulling it through an orbit around a chimney. But the motion of the imaginary birds and the birds I remembered from the evening was exactly identical.