Thanks for the comments all. I looked through more pictures in the same sequence of the shoot. I can't tell for sure, but I think I posted the same bird in the foreground and one from the background. Part of why I'm sticking with the ID is that some very good birders were at this location in Hamilton NJ as it drew the crowd for a Little Blue Heron and a Snowy Heron. They posted both the Least Sandpiper and Semipalmated Sandpiper. (In addition to a Solitary and Spotted -- but those I've seen and can ID).
So even these two pictures below. They look like different birds, unless they are at different stages. They both have yellow legs, although the one with more brown on it's back has yellower legs.
Then again, I'm lightening up the pix because of the shadows. Maybe they both are Least Sandpipers, and even around other birders telling me where the Semipalmated was, I'm just taking pictures of the wrong bird?