All of the following Red-throated Loon images were on the order of a 1/4 mile away, and are extremely marginal.

In this shot, you can see how far back towards the nape that the light area on the neck extends; much more than on Common or Pacific. This is a 1st-winter bird, though from even longer range when I 1st saw it I thought it was a white-throated adult. This bird has a very light grayish wash on the foreneck, and contrasts slightly in this photo to the white of the face.