Tundra or trumpeter swan? Utah. Usa (1 Viewer)

[Birdwatcher814]

There has been some discussion on the Facebook pages I follow on if this is a tundra or trumpeter swan. It was seen in northern Utah on the bear river migratory bird refuge a couple weeks ago. Most say trumpeter but because of the u shaped forehead pattern I am inclined to say tundra. Any thoughts? Here is the original blog post that has 3 more images. https://bearriverblogger.com/bird-watching-tundra-or-trumpeter-swan/

 

[Bird_Bill]

Tundra swan
-Shape of the skull, compared to the slope of the upper mandible of the bill. We see a pronounced change in the taper, following the slope to skull crown. Trumpeter would not show the top radius.

-Black of the bill does not fully embrace the eye orbit, rather it's narrower than the eye diameter.

-Grin line...been my experience that tundras are more thin lipped, while the trumpeter has a larger grin showing more red.

 

[Nikolai Kolev]

https://www.birdforum.net/showthread.php?t=37199
I have the similar question, and nobody anser me.