I am in an urban neighborhood in central San Diego, CA, and for the past couple weeks (late April, early May 2020) I have been hearing this (attached) bird just about every morning. I've never been able to locate it, so have not seen it. In fact, as soon as I step outside my house, it goes quiet.
It reminds me of a bobwhite! (I'm from the midwest) but we shouldn't have them here in San Diego.
Song Sleuth is not helpful at all because of the chatter of the other birds in the background.
New Recording 5.m4a