Bittern is a common name given to birds belonging to the subfamily Botaurinae of the heron family Ardeidae. Bitterns tend to be shorter necked and more secretive than other members of the family. The genus Ixobrychus contains mainly small species: Australian little bittern, Ixobrychus dubius; Black bittern, Ixobrychus flavicollis; Cinnamon bittern, Ixobrychus cinnamomeus; Dwarf bittern, Ixobrychus sturmii; Least bittern, Ixobrychus exilis; Little bittern, Ixobrychus minutus; Schrenck's bittern, Ixobrychus eurhythmus; Stripe-backed bittern, Ixobrychus involucris; Yellow bittern, Ixobrychus sinensis.
The genus Botaurus is the larger bitterns: American bittern, Botaurus lentiginosa; Australasian bittern, Botaurus poiciloptilus; Eurasian bittern or great bittern, Botaurus stellaris; South American bittern, Botaurus pinnatus.
Finally, there is the Zigzag bittern /heron, Zebrilus undulatus.
See: Black bittern, Great bittern, Little bittern.