The species differs from the slightly smaller nominate form through its paler upperparts, brown-tinged underparts and a brown stripe through the eye.

As indicated above, it has different vocalisations to the other forms, and is now usually given full species status, although its behaviour, nest and eggs are identical to those of other subspecies of water rail.

[5] It was restored as a full species, the eastern water rail, R. indicus, by Pamela Rasmussen in her Birds of South Asia (2005).

[8] A 2010 study of molecular phylogeny further supported the possibility of specific status for R. a. indicus, which is estimated to have diverged from the western forms around 534,000 years ago.

[5] The breeding birds on the Japanese island of Hokkaido mostly migrate well south including to Korea but a few remain during winter in the coastal marshes of Honshu.