Just when I thought we'd foiled old Procyon lotor (better known as the Common Raccoon) he switched the focus of his nocturnal mischief to our other bird feeder.
Adding a 5 pound weight to one of the bird feeders prevented him from pulling it up into the tree and dumping out the seeds.
He just scampered over to the next branch, pulled up the other feeder and dumped it out. Wikipedia says that their natural predator is the cougar. I called Petsmart, but they're fresh out of mountain lions so I'll have to keep trying on my own.
Edited to add: This post was written by Dan who was also the mastermind behind adding the weight to the bird feeder. I gotta admit, I was pretty impressed.