I shot several shots of the flock as it lifted off once, just to see what I might find or find any additional Lesser Black-backs. I didn't see this possible adult Thayer's Gull at all. The outstretched wing with very limited black in the primaries appearing as just streaks is a typical Thayer's pattern. NOTE: a very small proportion of Herring in the east can show a very similar pattern (seems to be more prevalant in the extreme NE), I haven't seen a Herring in the mid-south with this pattern but possible.