In the last 2 weeks or so, I’ve been hearing a really loud bird singing - but he (I’ll assume it’s a he) starts his song right around sunset. It’s a fairly complex song, at first I wasn’t sure it was even a bird. I’ve never really noticed birds singing at night, is this some sort of spring time mate finding plan, perhaps? Normally, the singing begins almost exactly as the sun completely disappears on the horizon, but a few times there have been bursts of song at 2 or 3 in the morning.
FWIW, I’m in the Bay Area.
Perhaps there are some ornithology enthusiasts here that could ID this little musical guy?
Probably a mockingbird. They will sing anytime.
I think that’s it!
I found this page with a song sample, and it’s pretty much it:
http://www.learnbirdsongs.com/birdsong.php?id=4
As an added bonus, playing the song on that page made my dog go crazy. He was desperately trying to flush out the rascally bird that had clearly hidden in the laptop. 
They can be annoying, and can keep you up at night. Oh, sometimes you just want to kill a mockingbird!
Yes I also hear those guys occasionally in the middle of the night. I wonder who they’re talking to & what they’re saying.
If you can catch it, you can make a tasty margarita, otherwise called a “Tequila Mockingbird.”
They crack me up. Like nature’s little car alarms.
Tomorrow’s dinner.
I played that and now my cat is all freaked out looking for a bird in the sofa cushions next to me.
I played it for mine, and she just looked at me like I was fucking nuts. Didn’t even get out of bed.
Aha. A proper cat.
I love this place!
The thread started with vague question, received a factual answer right away, degraded into puns, and finally, wrapped up with a comparison of everyone’s cat’s reactions to bird songs.
If that’s not the SDMB in a nutshell, I don’t know what is! 
Thanks!
You may have found your bird, but I’ll mention that we have a robin who begins singing at about 4:00 AM, quite loudly and pretty much until the sun is all the way up.
Nice wordplay.
Could also be a whip-poor-will or chuck-will’s-widow, both nocturnal birds. I had a few of the latter sing in the field outside my old house, bugged me the first time, but once I found out what they were they ended up serenading me to sleep.
You mean mimus pollyglottos. Give the bird its due.
Don’t forget to “knick-knack” and “paddywhack” before you do that.