Josh Klein developed a machine that trains crows to trade coins for peanuts. Literally, for peanuts.
So you fill this thing with peanuts and set it out, say, in a public park, and the crows will scour the ground for loose change, carry it to the machine, and drop it in a slot in exchange for food.
The project, dubbed “CrowBox,” made a big splash when he unveiled it back in 2007.
Complete plans for the CrowBox freely available online so you can roll your own. Link to MakeZine.