Semipalmated sandpiper

The semipalmated sandpiper (Calidris pusilla) is a very small shorebird. The genus name is from Ancient Greek kalidris or skalidris, a term used by Aristotle for some grey-coloured waterside birds. The specific pusilla is Latin for "very small".

It is sometimes separated with other "stints" in Erolia, but, although these apparently form a monophyletic group, the present species' old genus Ereunetes had been proposed before Erolia.

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".