The black bittern (Ixobrychus flavicollis) is a bittern of Old World origin, breeding in tropical Asia from Pakistan, India, Bangladesh and Sri Lanka east to China, Indonesia, and Australia. It is mainly resident, but some northern birds migrate short distances. It is a fairly large species at 58 cm in length, being by some margin the largest bittern in the genus Ixobrychus. Compared to related species, it has a longish neck and long yellow bill. The adult is uniformly black above, with yellow neck sides. It is whitish below, heavily streaked with brown. The juvenile is like the adult, but dark brown rather than black. They can be difficult to see, given their skulking lifestyle and reed bed habitat, but tend to fly fairly frequently when the all black upperparts makes them unmistakable.