Charrán de Sumatra Sterna sumatrana

A medium-sized, long-winged, long-tailed tern of warm tropical seas. Adults appear snow-white except for a thin black nape stripe that extends from the eye (often not very visible from a distance), black outer edge to outermost primary, and thin, long black bill. Hovers frequently while foraging and dips down daintily to pick prey from just below the water's surface. Flies quickly and lightly, often associating with Bridled, Roseate, and Crested terns. Breeds colonially on rocky oceanic islands and headlands. Call a grating “grrri.”