In the shadow of London’s National Gallery and the church of St. Martin-in-the-Fields lies Trafalgar Square, with bronze lions the size of our car. Now, moreover, they can be seen as intended; until a few years ago they were famously covered in pigeon poop.
My college in Missouri had this problem when I went to school there; we students loved feeding the pigeons, but they had a tendency to exert the prerogative of flying animals. The college responded, as I recall, by setting out poisoned feed, killing not only the pigeons but, presumably, every other animal that ate the feed, and every animal that ate those animals. I don’t know what kind of poison they used, but I hope it was something that breaks down quickly in the soil once all those animals died.
Londoners had a wiser solution, one that cut down on the pigeons and kept the remaining ones fit: hawks. When I passed by an excited crowd were gathered around a Mr. and Mrs. Hawk, who seemed to regard the human herd with nonchalance.