This is really a question to further my own learning: I think I see black on the back of the head of the birds in flight in shots 1 and 3. Does the black on a non-breeding Forster's actually wrap around the back head like that? I thought the black on FOTE was generally restricted to big eye patches, creating the impression of a mask.
I get that FOTE is less uncommon inland (and an ebird search bears this out). So could it just be incomplete molt on the bird in flight, with it's wrap-around black head and white crown?