It is a very small bittern; at 27–36 cm in length, 40–58 cm wingspan and 60-150 g weight. The smallest specimens are perhaps the smallest herons on earth. It has a short neck, longish bill and buff underparts. The male's back and crown are black, and the wings are black with a large white patch on each wing. The female has a browner back and a buff-brown wing patch.
