All good ideas!
And I've thought about the idea that the ground coulb be transmitting some kind of vibration from the feeder. But for the life of me I can't hear it making any noise in the minute before it goes off even when I'm right next to it. They certainly know to come to the sound of a 4-wheeler or my old jeep (because I always feed them extra).
I guess I'm going to go with the plankton count idea.
Hmmmmm... they must carry little calculators as well.
