Anyone who puts out food for wild birds quickly learns that the squirrel food alert network is very efficient. Within hours, often before the birds find your new feeders, the squirrels are on site, shoveling sunflower seeds into their mouths as fast as they can. That’s pretty fast.
Some people actually like squirrels. That’s fine with me. If they want to feed expensive seeds and nuts to squirrels, let them go right ahead. Of course, their largess will encourage the production of more squirrels….
On the other hand, most bird feeders want to feed birds, not rodents. Banging on the window and waving your arms may alarm the neighbors, but it won’t faze the squirrels for long. So what’s a frustrated bird lover to do?
Sex in your Garden, by Angela Overy

I recently read a book that I just have to recommend.