Invisible Rail
A species of Habroptila Scientific name : Habroptila wallacii Genus : Habroptila
Invisible Rail, A species of Habroptila
Botanical name: Habroptila wallacii
Genus: Habroptila
Content
Description General Info
Description
The invisible rail is a large, 33 to 40 cm (13–16 in) long, flightless bird. The adult has a mainly dark slate-grey body, dark brown plumage on the lower back, rump and wings, and a black uppertail. Its underparts are slightly paler slate-grey than the back, and the bare skin around the eye, the long, thick bill and the strong legs are bright red. It has a small spine at the bend of the wings. The sexes are identical in appearance; the plumage of fledged immature birds has not been described. The invisible rail is superficially similar to the purple swamphen, Porphyrio porphyrio, which has recently been found in Halmahera, but that species is larger, with a short, thick red bill and a red forehead shield; it also has purple underparts and a white undertail. The invisible rail is different from the Calayan rail, Gallirallus calayanensis, in that it is larger and lacks the barred plumage of that species; there is no overlap between the ranges of the two species. The call is a low drumming, accompanied by a tuk, tuk, tuk made with the wings. The nature of the vocalisation led to a local legend that the sound is made by the bird beating on a hollow tree or branch with its feet. Gerd Heinrich noted the local name "soisa", meaning drum, and described the call as being a subdued drumming purre – purre – purre – purre – purre which sometimes ends in a loud shrill scream. The bird also produced a dull hum similar to the voice of the banded pig (Sus scrofa vittatus) and reminiscent of the call of the snoring rail (Aramidopsis plateni). Calling is most frequent in the early morning or late evening, and a human tapping a sago stem with a machete may elicit a response from the bird. A quieter version of the call is given at the nest. Other sounds attributed to this rail, such as loud screams, may be incorrect, since they are like those produced by the pale-vented bush-hen (Amaurornis moluccana). 
Size
35 cm
General Info
Behavior
The difficult habitat and retiring nature of the invisible rail mean that information on its lifestyle is sparse, and there are few confirmed sightings. Recorded food items include sago shoots and insects. It also feeds at cut sago plants, although it is unclear whether it is eating the decaying plant or searching for other edible items. It swallows small stones, as do all rails, to help break up its food in the gizzard. The invisible rail is thought to be monogamous, but little else is known of its courtship behaviour prior to nesting. A report of 4–5 striped chicks was long thought to be incorrect, since such a plumage is not normal for rails. In this family, chicks are typically precocial, downy and black, with any ornamentation confined to the head, bare flesh, or specially modified plume feathers. The issue was resolved in November 2010 when a nest was found in the top of a rotting tree stump, 1 m (39 in) above ground level and 46 m (151 ft) in from the edge of a dry swamp forest in Aketajawe-Lolobata National Park. The nest depression was 15 cm (5.9 in) in depth, with a lower layer of small wood chips at its base and a lining of dead leaves. The egg shells were brownish-white with dark brown and black markings of different sizes. The two very young chicks were entirely covered in black down, contrasting with a white pollux (the equivalent of the thumbnail on a human hand) and pink index nail. The bill was black with a white tip, and the legs were black-streaked brown. The eyes had grey irises and blue pupils. Rail chicks leave the nest soon after hatching, so the chicks were assumed to be only a day or two old.
Distribution Area
The invisible rail inhabits the dense, spiky sago swamps of Halmahera, particularly where forest adjoins the boggy areas. Claims that the rail occurs in alang-alang grass are thought to have arisen from confusion with the pale-vented bush-hen. German ornithologist Gerd Heinrich, who prepared for his Halmahera trip by rolling in stinging nettles, wrote of the sago swamp habitat in the 1930s: I am solidly confident no European has ever seen this rail alive, for that requires such a degree of toughening and such demands on oneself as I cannot so easily attribute to others. Habroptila is shielded by the awful thorns of the sago swamps... In this thorn wilderness, I walked barefoot and half-naked for weeks. Sightings of the rail from 1950 to 2003 were from a restricted area of West Halmahera Regency, at the base of the western peninsula of the island, but it was recorded prior to 1950 as far as the southern point of Halmahera. More recent records showed that it is still present in a significantly larger area, including the northeast of the island, and locals claim that it also occurs in the swamps near Kao, in the northwest.
Species Status
Bird species with a restricted range are especially vulnerable to human activities, and eight of the 26 bird species occurring only in the Northern Maluku Endemic Bird Area are threatened, including the invisible rail. Almost a quarter of all rail species have conservation concerns, and flightless island species are particularly at risk, at least 15 species having become extinct since 1600. The estimated population of the invisible rail is 3,500–15,000 birds, and its restricted range and small population mean that the species is classified as vulnerable by the International Union for Conservation of Nature (IUCN), although this rail is so poorly known that it may be more common than the estimates suggest. Habitat loss has occurred through commercial harvesting of the sago, or conversion to rice cultivation and fishponds. The rail is a prized food for local people who catch it with traps made from strings of bark and hunt it with dogs. The only described nest was in an area well-used by local villagers, and the rail may be more adaptable to habitat changes than had been thought. There were also several sightings in northeast Halmahera in 2008 and 2011, extending the area in which this bird has been seen in recent years.
Scientific Classification
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