in particular the flight feathers are degenerate, as the barbules on many of the feathers (but not all, as has sometimes been reported) fail to interlock, giving the feathers a ragged appearance. 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 . The Inaccessible Island rail has a low basal metabolic rate (BMR), measured in 1989 at around 60–68% the rate expected for a bird of its weight. The scientists responsible for the study speculated that the low BMR was not as a result of flightlessness, which does not have this effect in other bird species, but was instead the result of the rail's island lifestyle. The island lacks predators and other competitors, and as such can be expected to be at full carrying capacity for rails. This in turn would favour energy conservation by the rails, resulting in small body size, low BMR and flightlessness. 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 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 rail is found in almost all habitats on the island and at all altitudes, from sea-level to . It reaches its highest densities in fields of tussock grass (Spartina arundinacea), with 10 birds per hectare, and in tussock grass mixed with ferns (Blechnum penna-marina) and sedges, with 15 birds per hectare. This habitat is found close to the shore and surrounds most of the island on the steep cliffs. 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