Dunlin
Calidris alpina
Measurements: Length: 16–20 cm (6.3–7.9 in) Weight: 34–77 g (1+1⁄4–2+3⁄4 oz) Wingspan: 38–43 cm (15–17 in) An adult dunlin in breeding plumage shows the distinctive black belly which no other similar-sized wader possesses. In winter, dunlins are greyish-brown above and white below. Juveniles are brown above with two weak whitish "V" shapes on the back, though less obvious than the same feature on little stint and some other species in the genus. They usually have black marks on the flanks or belly. All ages show a narrow white wingbar in flight. The legs and slightly decurved bill are black.
ID text from Wikipedia, CC BY-SA 4.0
Semipalmated Sandpiper
Calidris pusilla
It is a small sandpiper, 15–18 centimetres (6–7 inches) long and weighing around 18–51.5 grams (0.63–1.82 ounces). Wingspan ranges from 13.8 to 14.6 in (35 to 37 cm). Adults have black legs and a short, stout, straight dark bill. The body is dark grey-brown on top and white underneath. The head and neck are tinged light grey-brown. This bird can be difficult to distinguish from other similar tiny shorebirds, in particular the western sandpiper; these are known collectively as "peeps" or "stints". Jonsson, Lars & Peter J.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
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