There is a new article that just came out in Arizona Birds on swan
identification.
Pierre Deviche contacted me almost two years ago regarding swan ID for a
juvenile swan found in Arizona. It turned out to be a tundra swan. Then
another juvenile swan showed up this year. The controversy over Trumpeter
or Tundra raged for a bit. I spend considerable time honing my skills on
Tundra vs Trumpeter juvenile ID, all kinds of characteristics and looking
at many photos. It was a great learning opportunity. Then, Dr. Deviche and
Doug Jeness wrote a paper on swan ID as it relates to the Arizona
geographic area. It is worth the time to read and the photos are useful.

https://arizonabirds.org/journal.html

Martha Jordan
Everett, WA