Sanderling

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. They then burrow rapidly down again as the water retreats. They leave no marks on the surface so the sanderlings hunt for them by plunging their beaks into the sand at random, consuming whatever they find. Their bills can only penetrate two or three cm and as the water swirls around and retreats, the sand is softer and this makes it easier for the birds' beaks to penetrate further. In the spring, when much breeding activity is taking place in the benthic community, there may be as many as 4000 invertebrates per square meter, but their average size is smaller than later in the year. The birds appear to rush madly around at the edge of the surf but in reality they are maximizing their chances of catching as many prey animals as possible when they are at their most vulnerable near the surface.