Lyons store in Moncton carry the Hammerin' Crow Call, a green plastic model. (I think Better Buys has 'em too, only cheaper, just can't recall absolutely.)
Sometimes mine calls 'em in right proper.
Other times it makes them fly the other way.
I'm lucky because I know a place where a farmer buries his deadstock, only he doesn't bury it. He dumps the dead cows in a big trench and only buries 'em every few months. The place is full of crows that pick at the dead animals. My record there is 9 in one sitting, but I usually get three to five at one stand, then go for an atv ride, then return a few hours later for three or four more.
If you can find such a place, it's a guaranteed Ace in the hole.
It's also a good place where you can practice your calling in a live situation by calling and watching how the crows react.
I hunt crows quite a bit and they can be great fun.
ONce you drop one, sit still. In a few minutes, his buddy will usually come looking for him.
Don't leave your kills lying there if you plan to return. Crows are smart enough to know to skeedaddle if they see that there's a dead brother lying there.