PEW PEW PEW

It took me a long time to figure out what that "pew-pew-pew!" noise was in the back yard. I heard it nearly every night, and it would get faster and faster until it turned into a sort of hysterical whistling and shrieking. I always assumed it was a particularly irritating sort of bird, but I could never see what it was.

I know what it is now. It's a squirrel.

This is a particularly aggressive red squirrel who loves to chase off any birds who try to get at "his" food source, the two bird feeders, plus any fallout on the ground. He also "owns" the very desirable real estate in the corner of the yard, a clump of bushes and trees which he often has to defend against those evil warlords of suburban wildlife, the Black Squirrels. 

This squirrel gets so worked up, I fear for its mental health at times. Maybe that's where the expression "squirrely" comes from.