The Chatham rail (Cabalus modestus) is an extinct flightless species of bird in the family Rallidae. It was endemic to Chatham, Mangere and Pitt Islands, in the Chatham archipelago of New Zealand.[1] The Chatham rail was first discovered on Mangere in 1871, and 26 specimens collected there are known from museum collections. Its Māori name was "mātirakahu".
The Chatham rail and the Dieffenbach's rail, both extinct and flightless, were sympatric on the Chatham Islands. Their sympatry suggests parallel evolution after separate colonisation of the Chatham Islands by different rail ancestors.[2] A genetic analysis from 1997 suggested that the two were sister taxa.[3] However more recent genetic analysis finds them to not be closely related within the Gallirallus radiation, with a 2014 analysis finding the Chatham rail being sister taxon to the possibly extinct New Caledonian rail instead.[4]
It became extinct on the island between 1896 and 1900. The species is also known from 19th century bones from Chatham and Pitt Islands. It is likely to have occurred in scrubland and tussock grass. Its extinction was presumably caused by predation by rats and cats (which were introduced in the 1890s), habitat destruction to provide sheep pasture (which destroyed all the island's bush and tussock grass by 1900), and from grazing by goats and rabbits. On Chatham and Pitt Islands, Olson has suggested that its extinction resulted from competition with the larger Dieffenbach's rail (also extinct), but this has been refuted later when the two species have been shown to have been sympatric on Mangere.[5] [6]