Anti-pigeon devices on top of billboards

Dear Matthew: Please, help. It’s driving me crazy. What the heck are those things on top of some billboards around town? You know, the things going around that look like radar or some kind of wind exercise. — Ron Fitzgerald, San Diego

Okay. I give. Here it is again. The single most asked question in the M.A. mailbag for the last several years. And the most answered (twice), despite my resolve not to repeat myself. So Ron, all the rest of you who have nothing to do but stare at the propellers on billboards — the whirly things are pigeon chasers. Keeps the birds off the billboards and the bird doo off the advertising. I’m sure I’ll be answering this one again in a year or so. Perhaps we can change it from a persistent aggravation into a cherished “Straight from the Hip" tradition.