The mystery shorebird is a Baird’s Sandpiper (Calidris bairdii)
This is a small, but relatively long-winged sandpiper. It is similar in size and appearance to the White-rumped Sandpiper (Calidris fuscicollis), but is buffier and has a dark rump. The two species share an elongated form, due to the long wing projection beyond the tail.
A key feature in the mystery photo is the dark rump—a White-rumped Sandpiper in this pose would show at least a hint of a white rump. The brownish upperparts (as opposed to grey), fine bill, and lack of streaking along the flanks also point to Baird’s Sandpiper.
If you answered correctly, congratulations! Don’t forget to check out WHSRN on Facebook for more shorebird fun this weekend!