But basically, he covered the surface with bottle caps and a slot they birds could knock the caps into and it would feed them. They'd knock the caps in accidentally, and get food. He learned in an earlier experiment where they had to press a button to get food that the button had to be relatively close to the food. There was an even earlier step where he just fed them randomly to get them interested in the feeder in the first place.
They're very trainable animals. Smarter than my dog it seems. They're much more willing to experiment and seem to learn very quickly. Training my current dog requires tons of patience. He experiments very little while alternately repeating a behavior I'm trying to extinguish. I have to work with him in extremely small steps. Very sweet, but oh so hard to train.