That's a whole lot of surveillance right there!
The Sound Of More And More Pigeons Pecking Seed Off A Glass Plate

After setting up a glass plate with contact microphone attached and spreading birdseed on top, Libby and Marcel of Free To Use Sounds captured the surprisingly soothing sounds of an increasing number of pigeons pecking at (and walking on) the glass. It sounds like a rain storm coming! And you know how I feel about storms. “You’re only happy when it rains.” Fact! “You’re only happy when it’s complicated.” Not true, I like it simple.