I've observed several non-breeding plumaged, Black-bellied Plovers on the causeway the last few days and have seen reports, with pictures, that they are seeing American Golden Plovers. From what I've recently seen on the causeway, I'm wordering if what they are seeing black-bellies in non-breeding plumage. The easiest way for me to tell is to wait for them to fly and check for black axillaries (wing pits).