Look for any visible field marks, including bill shape and body shape, and pay attention to where it is, what it's doing. Consider the lighting and don't assume coloration based on oddly lit photos.
I'll post answers and better photos in a week or so. In the meantime, enjoy!
|1. January 2022, Arrowhead Marsh, Oakland, CA|
|2. January 2022, Berkeley, CA|
|3. March 2022, Inverness, CA|
|4. March 2022, Inverness, CA|
|5. March 2022, Inverness, CA|
|6. May 2022, Tigard, OR|