Utterly unmistakable large shorebird: gleaming white adult has a black back, black flight feathers, and a very heavy dark bill, which is used to dispatch crustaceans and other invertebrates. Narrow dark smudge around the eye imparts a sleepy appearance. Juvenile similar to adult but back pale brown. Inhabits sandy beaches and shorelines, as well as coral outcrops, rocky coasts, and mangroves. Forages in flocks, often giving raucous, tern-like calls in flight.