One of the drawbacks of using shelled peanuts is that most birds love them - including pigeons. At the moment I have primarily pigeons coming to the feeder. A few of them seem to understand a bit what needs to happen to get food. A couple of them even found a way to cheat by jumping from the railing tot he platform and landing hard, to shake a peanut loose. They would do this over and over, though it only works once or twice. They were even jumping in pairs for extra impact. I had to steady the platform with a bucket of water. They still try it from time to time, but that loophole has been closed :)

Peanuts in the shell would be better since corvids love them, but pigeons can't open them up to eat them. I still put out some peanuts in the shell to attract jackdaws, and they seem to prefer them to shelled peanuts.

I am thinking of building another feeder that works with in-shell peanuts. The feed container and dispense mechanism would have to be significatly bigger, maybe made entirely from PVC pipe bits or a small bucket instead of a jar. The rest should work as-is. In-shell peanuts are much less dense than shelled, but can get jammed more easily due to more irregular shapes and surface friction.