The cinnamon bittern or chestnut bittern (Ixobrychus cinnamomeus) is a small Old World bittern, breeding in tropical and subtropical Asia from India east to China and Indonesia. It is mainly resident, but some northern birds migrate short distances.

It is a small species at 38 cm (15 in) length, though it is one of the larger Ixobrychus bitterns. Possessing a short neck and longish bill, the male is uniformly cinnamon above and buff below. The female is similar but her back and crown are brown, and the juvenile is like the female but heavily streaked brown below. When surprised on its nest or concerned, it assumes the characteristic attitude of bitterns, termed the on-guard. The neck is stretched perpendicularly, bill pointing skyward, while the bird freezes and becomes very hard to see among the surrounding reeds.

Source: Wikipedia