Sexes alike. Very light grey above; jet-black cap and nape, when breeding; white below; narrow, pointed wings; deeply-forked tail; bright yellow, pointed beak and red legs diagnostic. In winter, black on crown and nape reduced to flecks. Solitary or small flocks, flying about erratically; keeps to riversides, calm waters, large tanks; scans over water, plunging if possible prey is sighted; rests on river banks, noisy and aggressive, especially at nesting colonies (March to mid-June).