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
Sanderling
Calidris alba
The sanderling is a small plump sandpiper, 18–20 cm (7–8 in) in length. Its weight ranges from 40–100 g (1+1⁄2–3+1⁄2 oz). The winter bird is very pale, almost white apart from a dark shoulder patch. This is the source of the specific name, alba, which is the Latin for "white". Later in the summer, the face and throat become brick-red. The juvenile bird is spangled black and white, and shows much more contrast than the adult.
ID text from Wikipedia, CC BY-SA 4.0
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