This was first found in mid-December, 2019, at the South Coast Botanic Gardens, but was unidentified. Photos were missing critical views of the undertail. It was found again a couple weeks later, identification confirmed, then was seen by many in the following few weeks.
More photos, different angles
Identifying Myiarchus flycatchers is a challenge, with voice often being the best and final decider. Between Brown-crested and smaller Ash-throated Flycatchers (in adults, anyway) look for the rufous-brown color extending the full length of the outer tail feathers, all the way to the tip. Ash-throated has a darker brown tongue that wraps around cutting the rufous off. Check out the photos below of the Brown-crested Flycatcher to see what I'm talking about.
Perched and facing away.
In flight with tail spread.
Perched. Tail color pattern visible.
Perched in profile.