Charlie, crows have pretty keen attention to detail. I have shot crows over home made sillouettes and I have had them flare over the same. You don't need a lot of crow decoys to be successful, 1/2 dozen will do. Get some good full body decoys. The new Carry-Lite's are too big and bulky, stay away from them. Flambeau is about the best out there for the money.
This is a good price, buy the dozen and you can then sell 6 on Ebay.
http://www.wingsupply.com/decoys-acc...w-decoy-dozen/