Got out on the boat for a half day today. It wasn't quite calm enough to be able to find a lot of loons on the water; we had considerably more success chumming in the gull flocks. One contained an adult Thayer's Gull. It made a number of circles around the boat.
The eye in full sun in the photos is flecked smoky gray, though appeared dark in the field.
The bird stood out most as being a white-winged gull on the underside of the wings.
Here's the famous Venetian blind pattern to the upper primaries. Per the books Kumlien's and Kumlien's-Thayers integrades generally do not have a completely black leading edge to P9, and most lack any black on P5. This one has more black on the leading edge of P9 than our Thayer's gull at Tiscornia this winter.
Juvenile/first winter plumaged birds are the other most common age group to see. Here's a first cycle Thayer's with a first cycle Great Black-backed at Tiscornia from a week or so ago.