I dunno, maybe they are really happy or don't have opposable thumbs so they can't snap their little fingers.
My question is why do birds always poop on my favorite light colored jeans every time I hang them out to dry? I have 20 feet of space and if they are the only thing drying, those little creatures will land and let go. Out of 10 other items all from the same wash they still choose my fav's to foul up. Maybe Alfred Hitchcock knew something I don't.......

Have a great day in San Pedro and Merry Christmas where ever you are.

Speaking of Hitchcock
http://gadgets.boingboing.net/2008/06/19/the-birds-barbie-dol.html

If the culprits are Grackles, they do it out of sheer meanness.

i used to feed them on my deck for photos.
not any more.

This is the nerdy answer. I used to work for US Fish and wildlife and the National Zoo doing research on birds. There was this wonderful guy named Gene (Morton, I think) who studied why they sing. They sing as early in the day (Oh-dark-thirty) to announce they are on their territory, attract females, and to challenge those that want to fight for both. They sing certain songs certain times of year because of day length and temperature. They are sorta hard wired. He also studied how they sing, which is even nerdier. Isn't it wonderful that someone could make a living having a passion about birds singing?

could one consider the spine tingling, ear piercing, nails-on-the-chalkboard racket the Chachalacha's spew forth at 0600, singing?

Why do birds sing? Because they'd have to have lips to hum or whistle!

But they do whistle...sorta. Chachalakas just squawk...loudly!

Well, they don't have lips or teeth, they just have peckers. That keeps them happy with something to sing about.

no Chicken Lips?