I mentioned the difference in color on Bonaparte's gulls. Here are a few pics. Note that in our area we are more likely to see just the black dot on the head, which may help you to distinguish them from other gulls.
This pic represents what you are more likely to see, right now.
Some videos of these birds feeding, etc........
This is of Bonaparte's gulls on the water. You can see most of them have molted and are most easily identified by the black spot behind the eyes.
Loon looking for food......to me, they are one of our most interesting looking Winter birds....