カワアジサシ Sterna aurantia

Widespread inland tern of South and mainland Southeast Asia. Breeding adults have full black cap and pale gray wings; white belly, larger size, and heavier structure distinguishes this species from the less common Black-bellied Tern where their breeding ranges overlap. Non-breeding adult has patchy black on the head instead of a full cap, and juvenile has mottled brownish-gray back with a partial black “mask”. Favors freshwater sites, breeding on sandy islands. Gives a grating “kYYEER” note.