I live in the south bay area of Los Angeles. As long as I have been alive the little sparrows were everywhere. You could not go outside without the chirping just being part of the background noise.
I have not seen a single one around here in over 2 months now?? Nothing on the internet I can find, I do see them still a little north and a little south but not in the numbers I used to see them. It would ne nice if they were gone but I still have to wonder why they are disappearing. I may have posted on this a couple of months ago. Any theories? I do know that in recent years the last of the open spaces have disappeared this may be all there is to it. We also had a west nile die off of crows in the area recently.