Seed Thief

I know for a fact that my squirrel-proof bird feeder is squirrel proof because I've seen squirrel after squirrel try and fail to get feed from the feeder on countless occasions. But this evening I was surprised to notice a chipmunk perched on the seed tray and helping himself to the seed. He had figured out how to climb the shepherd's hook and then jump over to the seed tray. He's just light enough that the seed tray doesn't give way like it does for heavier birds or squirrels. So, he had found his very own "fast food drive thru". It was dusk, so this picture didn't turn out very clear, but his cheek pouches were so full of seed that I don't know how he could have possibly found room for any more seeds. I don't know that there's anything I can do to keep him away, but if he tells all his friends I'm sure the seed will start disappearing rather quickly.