Inaccessible Island rail

Although the Inaccessible Island rail may have been known to the Tristan Islanders who visited the island annually to hunt seals, the species first came to the attention of scientists during the Challenger expedition of 1872–1876. When the expedition visited the island in October 1873, Sir Charles Wyville Thomson learned of the species and recorded observations made by two German brothers, the Stoltenhoffs, who had been living on the island for the last two years. Thomson was unable to collect a specimen. Another attempt was made to collect a specimen by Lord Crawford on his yacht Valhalla in 1905. A final attempt was made during the Shackleton–Rowett Expedition, which passed by in April 1922 on its way back to Britain. This visit also failed, but members of the expedition left collecting material with a Rev. H. M. C. Rogers, then chaplain on Tristan da Cunha. The following year two study skins arrived in the Natural History Museum, London, followed soon after by another skin and a specimen in spirits. Physician Percy Lowe was then able to use the skins to describe the species. He did so, briefly, at a meeting of the British Ornithologists' Club, in 1923. ==Evolution and taxonomy==

Prior to its collection it had been assumed by Thomson that the species was close to the other "island hens" known in the Atlantic, possibly a gallinule, The generic name Atlantisia was named for the mythical island of Atlantis, destroyed by a volcano. The specific name rogersi honours the Rev. Rogers, who collected and sent the first specimens of the species to Lowe. In his 1928 paper on the species, Lowe thought the Inaccessible Island rail was the descendant of flightless ancestors which had reached Inaccessible Island via a land bridge or sunken continent such as Lemuria. Land bridges were commonly invoked to explain biogeographical distribution patterns before the development and acceptance of plate tectonics. By 1955 it was understood that the rail was the descendant of ancestors that had flown to Inaccessible Island. It was also presumed that, like most other land birds of the Tristan Archipelago (except the Tristan moorhen Gallinula nesiotis and the Gough moorhen G. comeri), it had probably reached the island from ancestors in South America. The most recent comparative morphological study to include the genus, in 1998, placed it in a subtribe Crecina of the crakes. Its exact position could not be determined, but it was suggested to perhaps be the sister taxon to the genus Laterallus, a genus of small crakes found mostly in South America. Two extinct flightless species of rail were at one time placed in the genus Atlantisia with the Inaccessible Island rail. The Ascension crake (Mundia elpenor) and the Saint Helena swamphen (Aphanocrex podarces) were once considered congeners of A. rogersi. The Ascension crake disappeared some time before 1700 but was briefly mentioned and described by traveller and hobby naturalist Peter Mundy in 1656. The Saint Helena swamphen disappeared before 1600 and has never been encountered alive by scientists. In 1973 Olson synonymised the genus Aphanocrex with the genus Atlantisia, and described the Ascension crake as being congeneric. Stervander et al. (2019) resolved the taxonomic affinity and evolutionary history of the Inaccessible Island rail by phylogenetic analyses of the DNA sequence of its full mitochondrial genome and a handful mitochondrial and nuclear genetic markers. According to this study, the Inaccessible Island rail belongs to a clade comprising its sister species, the dot-winged crake, the black rail (Laterallus jamaicensis) in America, and most likely the Galápagos crake (Laterallus spilonota), therefore suggested referring the Inaccessible Island rail to the genus Laterallus. It colonized Inaccessible Island from South America c. 1.5 million years ago. ==Morphology==

The Inaccessible Island rail is the smallest living flightless bird in the world, measuring . Males are larger and heavier than females, weighing , average , compared to , average , in females. It is dark chestnut-brown above and dark grey on the head and below, with degraded white barring on the flanks and belly, and adults have red eyes. The female is similar to the male but with paler grey and a faint brown wash on the underparts. It has a black bill, which is shorter than the head. The wings are reduced and weak, and smaller than same-sized flying relatives, as is the sternum. The tail is short, in length, and the and are nearly as long as the tail . A comparison of flighted and flightless rails, including the Inaccessible Island rail, found that rails that lose the ability to fly also have low BMRs. ==Distribution and habitat==

The Inaccessible Island rail is endemic to the uninhabited Inaccessible Island in the Tristan da Cunha group in the mid-Atlantic Ocean. The island is in area and has a temperate wet oceanic climate with high rainfall, limited sunshine and persistent westerly winds. The Inaccessible Island rail can also be found in upland fern-bush heath, dominated by wind-stunted tree-ferns (Blechnum palmiforme) and in the island forest in the central plateau which is dominated by Island Cape myrtle (Phylica arborea)—which can reach where sheltered—and Blechnum palmiforme. In both these habitats the population is estimated to be two birds per hectare. It will also forage among boulders on the beaches, but has not been found in the short dry grasses on the cinder cones (the scientists making the observations cautioned that this does not mean that they never use the habitat). It frequently uses natural cavities among boulders or tunnels through grasses created by frequent use to move around while concealed. ==Behaviour==

The Inaccessible Island rail is territorial, and the territories they defend are tiny. The territories in the tussock grass habitats around Blenden Hall, where the population densities are highest, extend to . The small size of the territories makes encounters between families and individuals frequent, and confrontations and territorial calling are common. On meeting, confrontations start with loud trills or twittering, then birds may face off, standing very close to each other and displaying ritually with their heads lowered and their bills pointed towards the ground. They may circle, and continue displaying until one bird slowly retreats or a quick skirmish ensues and one bird is driven off. The incubation period for the species is not known, but both sexes incubate the clutch, although the males incubated for longer in the observations that have been made. Both sexes bring food to their partner that is incubating, which is either consumed on the nest or close to the nest. Changeovers of incubation details are preceded by "chip chip chip" calls, which become louder and more frequent the longer its takes the partner to respond. The eggs hatch within between 23 and 32 hours of each other and can be preceded by the chick in the egg calling for up to 45 hours before hatching. One hatching was recorded as taking 15 hours to complete. Newly hatched chicks are covered by downy black plumage, the legs, feet and bill are black, and the mouth is silvery. ==Ecology==

Lowe speculated in his 1927 paper that, in the absence of mammalian predators on the island, the brown skua would be the Inaccessible Island rail's only predator. After hearing another rail make an alarm call, adult Inaccessible Island rails become alert, while chicks fall silent. Adults are rarely preyed upon, but the mortality of chicks is high and predation by Tristan thrushes is a major cause of death. but were later lumped into the widespread species in 1974. ==Threats and conservation==

of the Inaccessible Island rail The Inaccessible Island rail has a tiny global range with a single population. Though still common within its tiny range, with around 5,600 adult birds in the world, Insular rails, particularly flightless species, are vulnerable to extinction. House mice, feral cats and brown rats, all of which would be a serious threat to this species, are not present on the island, nor have they ever been, but are present on nearby Tristan da Cunha, and could reach the islands via fishing vessels or other boats visiting the island (mice have been found on boats visiting the neighbouring Nightingale Island). Several conservation measures have been undertaken or proposed to protect this species. Inaccessible Island was once suggested as a site for agriculture for Tristan Islanders, which would have reduced habitat and risked the introduction of invasive species. Introduced New Zealand flax has been removed from the island, and the island now has a management plan. Other suggestions for securing this species' future include increased education on biosecurity for the local community, and potentially setting up a captive population. It has also been suggested that backup populations be established on other secure islands, for example Nightingale Island, in case predators reached Inaccessible Island, but this may have negative impacts on the endemic invertebrate faunas of these islands. ==See also==