Idea: Cheap, safe long-term city-wide rodent control.

Problem. We have a lot of mice and rats in urban areas such as Boston and New York. Pest control is expensive and uses poisons.
Possibilities: Natural extermination/pest control. There are virtually no mice or rats in certain areas of London (near Crystal Palace Park) or Bangalore, India. Why? Simply because the foxes in Crystal Palace Park and the stray dogs & crows (which are raptors or birds of prey) in Bangalore pretty much decimate the rodent population. The only rat I ever saw in Bangalore was the silhouette of the tail and the rear end of one flying away as the rest of it was in the maws of a flying crow. Kinda disgusting but cool. Unscientifically confirmed my hypothesis that Rentokil would go out of business if we brought this concept to the US.
Solution: have stray cats & crows in the city. Stray dogs can get dangerous and foxes don't seem to be a good solution for cities. They appear to be wild and stay away from humans unlike dogs. Cats appear to be a good solution: stray cats will thrive on the rodent population, won't attack people and self-regulate their population (more rodents, more cats; less rodents, less cats).

Note: Since I wrote this, I have read that cats do bite people sometimes. The incidence seems to be a lot less than dog bites, though. If cats were bred for rodent control, spayed/neutered and sent out to hunt, monitored via GPS and given rabies shots, it might work better. Would that still be cost-effective?