Another photo of hostile architecture in San Francisco. These nasty looking spikes are designed to keep pigeons from roosting wherever they are installed. I do believe they worked, but sadly nearly every pigeon I saw in SF had mangled, deformed feet. Many of them were missing toes and hobbled around when they walked. It was messed up.
I recently listened to a story about London's attempt to keep pigeons out of a famous public square (the name escapes me). Anyway, they hired falconers to hang out with their hawks every day and this kept the pigeons away. This may not be practical for every city, but it sure beats maiming birds!