A virtuoso of a bird, I just stood there recording in wonder as it went through its impressive catalog of impressions of Carolina Wrens, Blue Jays, cardinals, and more. The only other birds vocalizing here are House Sparrows chirping near the beginning, and I think a starling made a noise sort of near the end. Sadly it was right next to a road, but you can still hear the song over the passing cars.

My analysis of the birds mimicked in the song:

Starts with a titmouse scold, then a single Blue Jay call, then several different Carolina Wren songs in a row (which is interesting to me - did it hear them all together from one bird, or does it somehow know all those come from one species? That seems unlikely, but… ?)
:08 I don’t know those trilling calls, and then it makes what I consider its own noises.
:15 Red-bellied Woodpecker sounds, followed by maybe flicker sounds?
:24 quiet House Finch sounds and some odd metallic peeps, rolling directly into
:27 Carolina Wren
:36 “whinnying” - not sure what this is
:37 one quick Red-bellied Woodpecker “kwirr”
:38 Northern Cardinal
:43 Blue Jay
:44 House Finch
:45 Tufted Titmouse
:47 American Robin
:48 Carolina Wren
:52 Grey Catbird “meow”
:53 mockingbird sounds
:54 Flicker (I think) “wika-wika”
Then some high-pitched sounds I can’t ID
1:04 Carolina Wren

I encountered two on manzanita, and this one was very clearly sticking its rostrum into a marginal leaf gall (Tamalia?). Perhaps it was predating insect larvae within the gall, because these galls tend to be hollow without much juicy stuff to suck on.