And then they all shut up at once? I just moved, and there’s a huge tree right outside my window which I think is a resting ground for every sparrow that’s not busy picking up fries over at Disneyland. They all chirp and once and make a lot of noise, then suddenly they’ll all just stop!! Not little by little, they just all are silent at exactly the same time. Weird. Anybody know why?
SW
Go rent Hitchcock’s The Birds. It explains everything.
PS- You don’t live next to a gas station, do you?
Interesting question, MrsB! I never noticed the singing thing, but I’ve always been fascinated by the way a flock of starlings can all simultaneously change direction, as if there were a “flock-leader” somewhere directing the aerial ballet.
I don’t know why fortune smiles on some and lets the rest go free…
T
MrsBWayne,
What about the parrots? I’ve seen them in O.C. for about a decade, and now I’m seeing them at home in L.A. Anyway, they seem to squak noisily for an hour, then fly off somewhere else.
Nope, don’t live next to a gas station. What does that have to do with it?
At least they sleep at night.
I haven’t seen any parrots around. Maybe I’ll take a closer look up in that tree… well, maybe not. 
Most birds will cease singing and “freeze” when a threat seems apparent. They are quiet for two reasons:
Thus, when one bird shuts up in response to a possible threat, the others will follow suit. A cat walking by, a hawk flying over, or just the sound of a dog barking excitedly nearby is enough to trigger the phenomenon.
FixedBack
“When learned men begin to use their reason, then I generally discover that they haven’t got any.”~~*G.K.Chesterton 1908 *
I can bet you find your birds are most active singing out their little hearts around dawn or predawn. I don’t know the details, but birds tend to be most active at this time and then the hubbub dies down. (Of course, we had one dumb mockingbird who started at 3am! Must have been that proverbial “early bird”!)
Supplemental WAG: Their chirps may be just hunger cries. The husband bird is begging the wife to get up and fix some breakfast while the wife bird is telling him to get his lazy, fat tail feathers up and fix his own @&%*$ breakfast!
Sorry, lame joke on my part. There is a scene in The Birds* where a rampaging flock of birds actually blows up a gas station. There are also scenes where the birds will stop squawking just before attacking someone. Very creepy!
Don’t tell Krispy; but they are responding to the alien signals coming from behind the clouds! 
Bird vocalize for mating or territorial reasons.
So they are not “singing,” they are actually cussin’ and talking dirty.
Just like heavy metal rock singers?