Sanderlings are medium-sized “peep” sandpipers recognizable by their pale non-breeding plumage, black legs and bill, and obsessive wave-chasing habits where they run back and forth on the beach, picking or probing for tiny prey in the wet sand left by receding waves.
You’ll most often see Sanderlings in non-breeding plumage, when they are very pale overall: light gray above and white below, with a blackish mark at the shoulder.
In spring and summer, Sanderlings are spangled black, white, and rich rufous on the head, neck, and back.
At all times, their legs and bills are black.
In flight, white wingstripes contrast with their dark wings.
These extreme long-distance migrants breed only on High Arctic tundra, but during the winter they live on most of the sandy beaches of the world.

1st photo: Schiermonnikoog, The Netherlands, 17 February 2007
2nd & 3rd photo: Texel, The Netherlands, 19 October 2018
4th photo: Egmond aan Zee, The Netherlands, 29 May 2021
5th photo: Brouwershaven, The Netherlands, 24 October 2018