| Invisible Rail | |
|---|---|
| Invisible Rail | |
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Gruiformes |
| Family: | Rallidae |
| Genus: | Habroptila G.R. Gray, 1861 |
| Species: | H. wallacii |
| Binomial name | |
| Habroptila wallacii Gray, 1860 |
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The Invisible Rail (Habroptila wallacii) is a flightless species of bird in the family Rallidae (rails), endemic only to Halmahera, north Maluku, Indonesia, especially its swamp forests, wetlands, and forest edges. The Invisible Rail is evaluated as Vulnerable on the IUCN Red List of Threatened Species. It is the world's smallest living flightless bird.[2]
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The Invisible Rail was first classified by English zoologist George Robert Gray in 1860.[3] It is the only member of monotypic genus Habroptila.[3] It is known from only a handful of confirmed sightings and specimens—the most recent of which was in 2003.[1] This species may be related to the New Guinea Flightless Rail (Megacrex inepta).[4] Alternate names include: Wallace's Rail, Drummer Rail (Soisa), Halmahera, Râle de Wallace (in French), Trommelralle (in German), and Rascón de Wallace (in Spanish).[5][6]
It is a large, 330–400 mm (13–16 in) long, flightless rail.[3] Both sexes are similar in color, dark slate-grey with darker brown wing and tail plumage, bare red orbital skin, long reddish orange bill and legs. The undersurface is somewhat lighter in color. It makes a low drumming sound with loud screams. It is superficially similar to the Purple Swamphen (Porphyrio porphyrio) and Calayan Rail (Gallirallus calayanensis). It is different from the Purple Swamphen in its markings, which has been recently discovered to also reside in Halmahera, though is has been known to reside elsewhere for thousands of years. It is different from the Calayan Rail in that it is larger and some markings are different.[1][7] Confusion with both these species is likely. Of 26 bird species whose range is solely “Northern Maluku Endemic Bird Area”, the Invisible Rail is one of eight threatened species.[4]
The Invisible Rail is native to the remotest and densest parts of the sago swamp forests and wetlands of Halmahera, Indonesia,[6][8] favoring the edge habitats where swamp meets forests and clearings. Specific locales in that region where it has been sighted are Fanaha, Gani, Pasir Putih, Sondo, Tewe, and Weda Bay. There are also local reports of it living in the Kao sago swamp.[4] It is classified as vulnerable with an estimated population of 2500–9999. Causes of this vulnerability are ongoing habitat loss from agriculture and aquaculture, fragmentation, predation, small population size, limited range and hunting in some areas.[1][2] Its stealthy, skulking behavior and dense habitat make it especially difficult to study in the wild. Consequently, it is poorly known and may even be more numerous than believed.[1] Much of these sago swamps have been destroyed through sago extraction, predation, irrigation, conversion to wet rice fields, and fishpond development.[3] Natives hunt this bird with snares and dogs.[6]
Little is known of the Invisible Rail's life cycle. Its diet consists mainly of plant shoots, vegetation matters and insects. They also feed at open cuts of sago trunks.[4] The call is drum-like sound (hence the common name drummer) with a loud scream.[6] Flightlessness in birds is known to be related to changes in the pectoral girdle, flight feathers and body size, and was once speculated to also be related to brain size in birds. However, this has been proven to generally not be correlative to the flight capability of birds, except there is a correlation of flightlessness to small brain size in the Great Auk (Pinguinus impennis), the Kakapo (Strigops habroptilus) and some species of penguin.[9] Breeding is in pairs and 4–5 chicks are hatched. Local people feel that during the dry season this bird leaves the forest.[4]