Here's something from John Gross that I enjoyed reading.
"Hi, Paul. You recently ran a question from a reader regarding whether and how to confront bird feeders, people feeding white bread to the ducks at Manito. I had a girlfriend that could answer this question perfectly. She was fearless and quite pleasant. Qualities singularly suited for this question. If she saw you toss a butt, this in a time when people smoked and tossed butts, she'd pick it up and hand it back, 'Here, you dropped this.' If we were stopped at a light and you pulled up in your pickup with the dog in back...school's in session.
"She and I are no longer together but your reader's question brought back the memory. On the issue of feeding empty calories to wild birds, like your reader, I've seen this a number of times. The bird feeders are always enjoying the experience, invariably there are kids involved. My typically dour countenance does not lend itself to effective communication in this situation. What I've taken to doing is wandering over to one of the 'Don't feed the birds' signs. They're always close. I spend time pondering the sign, maybe glance over at the white bread party, and then move on. My old girlfriend would call that weak sauce and she'd be right."