I've been a falconer for 14 years, you certainly can use raptors to control some crop predators. But, it's a lot more complicated than just having them around. There's some good info here:
http://oregonfalconers.com/index.php/falconry/bird-abatement What kind of bird you use depends on what kind of problem you have. Harris hawks are great for controlling rabbits and sparrows/starling/pigeons at night and in enclosed spaces but they aren't very effective for controlling small birds eating your blueberries, cherries, etc. You need a falcon for that. All of which is stringently controlled by federal and state regulations (even in Canada you have to have permits to keep most birds of prey). You can't leave them alone, you can't correct them for killing a chicken, some species will nest on platforms but most won't, owls can't control avian farm pests, and you will never lose the "self-fry gene". The electrical companies can modify their setups to prevent electrocutions from happening though. If you see a bird get electrocuted on a pole or transformer you should contact the electrical company and ask them to fix it. Not only is it bad for wildlife, it can cause the neighborhood power outages. It's in their own best interest to fix the problem.
