I'd appreciate it too. Found junco feathers and a dead hermit thrush so far, and there are two cats in the yard at any one time. I plan to call the city and see what they can do to enforce their bylaw; it's actually illegal for cats to be wandering freely. But short of setting up camp in my backyard I don't know how they could really make a difference.
Technically you'd be within your rights to live trap the cats and then take them to a shelter as strays. I've considered taking a pic of the dead bird, of the offending cats, and postering the neighbourhood with a mock thank you note. Anyone who lets their cat wander from dawn to dusk isn't going to feel any kind of responsibility, though. So for now I'm throwing cold water at them with little result.