Ask a bird lover how he keeps the squirrels off his feeder and you get a lot of expletives deleted. It's instant apoplexy, and understandably so. Americans buy half a million tons of sunflower seeds annually to fill their feeders, and spend the winter trying not to fill the birds with the bushy tails. Every time you outwit them, they retaliate with another creative compromise of the laws of physics. But in our hearts, we all agree: who would want to live in an unsquirreled world?