Battle of the Squirrel

Squirrels love my bird feeder. Inevitably, birdseed only lasts a few hours in the feeder before they scoop it all out onto the ground. Then a few birds come and eat off the ground, but squirrels get most of it. I'd like to use nicer seed occasionally to attract more exotic birds, but it would disappear long before they arrived.

I've checked the local stores, and no one carries anything to keep squirrels out of birdseed. Then I read that plain old cayenne pepper would work, because birds don't sense spiciness like mammals do. So this weekend, I mixed some in with the birdseed and put it in the feeder with great expectations. But as you can see, it didn't slow this guy down at all. :( Any advice?