Inaccessible rail  (Atlantisia rogersi)

The Inaccessible rail is classified as Vulnerable (VU) on the IUCN Red List (1).

The Inaccessible rail (Atlantisia rogersi) is the smallest flightless bird in the world. It is characterised by the rusty-brown plumage of its upper body, dark grey underparts and the white barring on its flanks and belly. It also has grey legs, a short, black bill and red eyes. The juvenile Inaccessible rail typically has a brown body and dark eyes (2).

This species generally has a loud, quavering call, as well as other varying calls including a loud, harsh ‘chip’ alarm call (2).

The Inaccessible rail is aptly named after the isolated island where it is found, occurring only on Inaccessible Island, Tristan Da Cunha (2). Located approximately 1,700 miles away from South Africa, Tristan Da Cunha is the remotest group of islands in the world (3).

The Inaccessible rail occupies virtually the whole of the volcanic Inaccessible Island. It can be found in most vegetation types, at different elevations and even on very steep slopes (4). However, it is most abundant in tussock grassland, further away from cliffs and in the open fern-bush on the plateau (2). The Inaccessible rail also tends to inhabit areas where it can take shelter in tunnels when breeding, such as among boulders and lowland vegetation (5).

The Inaccessible rail is a monogamous species, which breeds between October and January (2). This species lives in family groups within small territories, consisting of approximately 10 to 15 birds per hectare (5).

Built beneath a dense cover of vegetation, the Inaccessible rail’s nest is intricately woven from surrounding vegetation, and accessed via a track extending for up to half a metre (4). This species usually has a clutch of two eggs (2).

The Inaccessible rail has an extensive diet, feeding on a wide range of invertebrates, berries and seeds (4).

Despite its abundance, the Inaccessible rail has been classed as Vulnerable on the IUCN Red List since 1994, largely due to its restricted island distribution. Small islands are at permanent risk from chance events such as the accidental introduction of alien species from neighbouring islands, as well as disease and natural disasters (2).

Chick mortality as a result of predation by the Tristan thrush (Nesocichla eremita) is relatively common; however, it does not pose a major threat to the Inaccessible rail population. There is, however, significant risk of Inaccessible Island being colonised by other predators such as the black rat (Rattus rattus) from Tristan Da Cunha, which could have a dramatic effect on the Inaccessible rail population (2).

The island on which the Inaccessible rail occurs is a designated nature reserve, and has restricted access (5).

Various conservation measures to protect the Inaccessible rail have been proposed, including surveys to obtain a current population estimate, in conjunction with monitoring of population trends. More research into the main causes of mortality is required, and strict controls need to be applied to visits to the island to minimize the risk of colonisation by introduced species (2).

Finally, it would be beneficial to promote awareness about the dangers to the Inaccessible rail of introducing alien species through inter-island transfers (2).

View information on this species at the UNEP World Conservation Monitoring Centre.

Learn more about the conservation of species on Inaccessible Island:

• RSPB - Inaccessible Island Seabird Monitoring Manual:
  https://www.rspb.org.uk/Images/InaccessibleIslandseabirdmon_tcm9-181044.pdf