Sanderling
The Sanderling, is a small wader. It is a circumpolar Arctic breeder, and is a long-distance migrant, wintering south to South America, South Europe, Africa, and Australia. It is highly gregarious in winter, sometimes forming large flocks on coastal mudflats or sandy beaches.
Sanderlings feed on invertebrate prey buried in the sand in the upper intertidal. In North America this largely consists of the isopods, Excirolana linguifrons and Excirolana kincaidii, and the mole crab, Emerita analoga. When the tide is out these crustaceans live in burrows some way beneath the surface. When the tide comes in, they move into the upper layers of sand so as to be able to feed on the plankton and detritus that washes over them with each wave.
The Sanderling breeds in the High Arctic areas of North America, Europe and Asia. In North America it breeds in the Canadian Arctic Archipelago, Nunavut, Greenland (and to a lesser extent Alaska), in Eurasia it breeds Spitsbergen, and areas of northern Russia from the Taymyr Peninsula to the New Siberian Islands. In the northern winter it has a nearly cosmopolitan distribution across the world’s marine coasts. It is a complete migrant, traveling between 3,000 to 10,000 km from its breeding grounds to its wintering sites. Birds that travel further also arrive later and leave sooner. The majority of adults leave the breeding grounds in July and early August, whereas juvenile birds leave in late August and early September. The northward migration begins in March at the southern end of their winter distribution.
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Text excerpts © Wikipedia – Photographs © H.J. Ruiz – Avian 101
H.J. Ruiz - Avian101 
Could these be in Hawaii? They look very familiar?
They are part of the Sandpiper family which are very similar. 🙂