I watched this the other night:
It is freaking amazing; you will never look at those obnoxious black birds the same way. In the opening scene, the narrator (Sigourney Weaver!) explains that the town in Canada had a crow problem, so they held a contest to see who could shoot the most as y of dealing with the problem. They managed to kill a single crow before the rest figured out how high to fly to avoid being shot, then told their friends.
It turns out that crows have developed smarts for much the same reason we did; they are omnivores and opportunists, just like humans. That lifestyle requires that you learn multiple methods for obtaining food, and to be good at all of them. Along with that comes the necessity of communal living, which means that communication becomes important.
They have also evolved tool use, and are actually much more impressive about it than monkeys and apes. They have been shown to memorize truck routes and traffic light patterns, all to ensure they get the good food.
So the next time you see a large, black, beady eyed bird watching you, it likely is plotting something against you. Maybe even to kill you (or at least your livestock.)