This is the other Tundra swan, look how much more pink is on the bill and the head looks much rounder. The pinching in of the feathering at the eye is typical for Tundra, like the eye is set on a Tee, where the Trumpeter's eye is enveloped and becomes a part of that dark area of the bill.

The nare (nostril opening) on the bill is centered on these two birds where on Trumpeter the nare is closer to the eye. On Trumpeter the distance from the bill tip to the nare is always about 2" and is a diagnostic measurement if you can hold one down long enough to measure;o)