The Semipalmated Sandpiper, Calidris pusilla is a very small shorebird.
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".
They are long distance migrants and winter in South America with some going to the southern United States. They migrate in flocks which can number in the hundreds of thousands, particularly in favoured feeding locations such as the Bay of Fundy. This species is a rare but regular vagrant to western Europe.
These birds forage on mudflats, picking up food by sight. They mainly eat aquatic insects and crustaceans.