Forster's Terns are very common in my neck of the woods (NC) in the winter. They are super easy to ID when in non-breeding plumage as they are the only tern that has a black patch completely isolated.
They have a really weird looking migration map, see below from the Cornell Website. How do the birds that are migrating from NC get to breeding locations? And where do the migrants that go through NY come from?? Strange.