Red-necked Stint
Calidris ruficollis
These birds are among the smallest of waders, very similar to the little stint, Calidris minuta, with which they were once considered conspecific. The red-necked stint's small size, fine dark bill, dark legs and quicker movements distinguish this species from all waders except the other dark-legged stints. It measures 13–17 cm (5.1–6.7 in) in length, 28–37 cm (11–15 in) in wingspan, and 21–51 g (0.74–1.80 oz) in weight.
ID text from Wikipedia, CC BY-SA 4.0
Temminck's Stint
Calidris temminckii
These birds are very small waders, at 13.5–15 cm (5.3–5.9 in) length. They are similar in size to the little stint (Calidris minuta) but shorter legged and longer winged. The legs are dull yellowish or brown, and the outer tail feathers white, in contrast to little stint's black legs and grey outer tail feathers. This is a rather drab wader, with mainly plain brown upperparts and head, and underparts white apart from a darker breast. The breeding adult has some brighter rufous and/or blackish mantle feathers to relieve the generally undistinguished appearance.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
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Play BeakBrainPhotos and recordings are credited to their authors under the licence shown. Full profiles: Red-necked Stint and Temminck's Stint.