My office is an 'L' shaped building with a chain link fence around the parking lot, tall trees around the perimeter, a block from the beach - every Monday morning there's seagull feathers and bird poop on the ground where the falcons swoop in and eat some dumbass seagull that was scavenging in our trash. I find bird heads with the spinal column attached, bones picked clean and mystery organs all the time. Very cool birds (the falcons). Never caught one in the act of pigeon or seagull murdering, but the feathers, bird parts and poop are a pretty sure sign of what's happening.