Invisible rail

The invisible rail, Wallace’s rail, or drummer rail(Habroptila wallacii) is a large flightless rail that isendemic to the island of Halmahera in North Maluku,Indonesia, where it inhabits impenetrable sago swampsadjacent to forests. Its plumage is predominantly darkslate-grey, and the bare skin around its eyes, the long,thick bill, and the legs are all bright red. Its call is a lowdrumming sound which is accompanied by wing-beating.The difficulty of seeing this shy bird in its dense habitatmeans that information on its behaviour is limited.Recorded dietary items include sago shoots and insects,and it also swallows small stones to help break up its food.It is apparently monogamous, but little else is known ofits courtship behaviour. The only known nest was a shal-low bowl in the top of a rotting tree stump that was linedwith wood chips and dry leaves. The two young chickswere entirely covered in black down typical of precocialnewly hatched rails. The estimated population of 3,500–15,000 birds and the restricted range mean that the in-visible rail is classified as Vulnerable by the InternationalUnion for Conservation of Nature (IUCN). Habitat losshas occurred through the harvesting of sago and conver-sion of the wetlands to rice cultivation, and the rail iseaten by local people. The described nest was in an areafrequented by local villagers, so the rail may be moreadaptable to habitat changes than was previously thought.

1 Taxonomy

The rails are a large and very widespread family, withnearly 150 species. They are small to medium-sized, ter-restrial or wetland birds, and their short bodies are oftenflattened laterally to help them move through dense vege-tation. Island species readily become flightless; of 53 ex-tant or recently extinct taxa restricted to islands, 32 havelost the ability to fly.[2]

The invisible rail, first classified by English zoologistGeorge Robert Gray in 1860, is the only member of themonotypic genus Habroptila.[1] The genus name Habrop-tila derives from the Greek habros, “delicate, pretty,splendid” and ptilon, “feather, wing";[3] wallacii com-memorates British zoologist Alfred Russel Wallace.[4]Local names include “soisa”, “tibiales” and “rèie”.[5]

This rail is related to the New Guinea flightless rail,Megacrex inepta, and the chestnut rail, Eulabeornis cas-taneoventris, all three Australasian genera probably beingderived from Amaurornis ancestors.[1][6] Storrs Olson ar-

gued that the genusMegacrexwas so similar toHabroptilathat Megacrex should be considered a junior synonym ofHabroptila, resulting in two species in the genus.[7] Thiswas further lumped in Sidney Dillon Ripley's 1977mono-graph of the Rallidae; he included Habroptila within thelarge genus Rallus. This suggestion was, however, notaccepted by Gerlof Fokko Mees, who pointed out dis-tinct differences in the shape and structure of the bill.[8]Amolecular phylogenetic analysis based on mitochondialDNA sequence similarity found that Habroptila is part ofevolutionary radiation within the broad genus Gallirallusthat took place around 400,000 years ago in the region.[9]

2 Description

Habroptila wallacii on a 2012 Indonesian stamp

The invisible rail is a large, 33 to 40 cm (13–16 in) long,flightless bird.[1] The adult has a mainly dark slate-greybody, dark brown plumage on the lower back, rump andwings, and a black uppertail. Its underparts are slightlypaler slate-grey than the back, and the bare skin aroundthe eye, the long, thick bill and the strong legs are brightred.[10] It has a small spine at the bend of the wings.[11]The sexes are identical in appearance; the plumage offledged immature birds has not been described.[10]

The invisible rail is superficially similar to the purpleswamphen, Porphyrio porphyrio, which has recently beenfound in Halmahera, but that species is larger, with a

1

2 4 BEHAVIOUR

short, thick red bill and a red forehead shield; it also haspurple underparts and a white undertail.[10] The invisiblerail is different from the Calayan rail, Gallirallus calaya-nensis, in that it is larger and lacks the barred plumage ofthat species; there is no overlap between the ranges of thetwo species.[12]

The call is a low drumming, accompanied by a tuk, tuk,tuk made with the wings.[10] The nature of the vocalisa-tion led to a local legend that the sound is made by the birdbeating on a hollow tree or branch with its feet.[5] GerdHeinrich noted the local name “soisa”, meaning drum,and described the call as being a subdued drumming purre– purre – purre – purre – purre which sometimes ends ina loud shrill scream. The bird also produced a dull humsimilar to the voice of the banded pig (Sus scrofa vittatus)and reminiscent of the call of the snoring rail (Arami-dopsis plateni).[13] Calling is most frequent in the earlymorning or late evening, and a human tapping a sago stemwith a machete may elicit a response from the bird.[10] Aquieter version of the call is given at the nest.[14] Othersounds attributed to this rail, such as loud screams, maybe incorrect, since they are like those produced by thepale-vented bush-hen (Amaurornis moluccana).[10]

3 Distribution and habitat

The invisible rail inhabits the dense, spiky sago swampsof Halmahera, particularly where forest adjoins the boggyareas. Claims that the rail occurs in alang-alang grassare thought to have arisen from confusion with the pale-vented bush-hen.[10][15] German ornithologist Gerd Hein-rich, who prepared for his Halmahera trip by rolling instinging nettles, wrote of the sago swamp habitat in the1930s:[16]

I am solidly confident no European has everseen this rail alive, for that requires such a de-gree of toughening and such demands on one-self as I cannot so easily attribute to others.Habroptila is shielded by the awful thorns ofthe sago swamps... In this thorn wilderness, Iwalked barefoot and half-naked for weeks.

Sightings of the rail from 1950 to 2003 were from a re-stricted area of West Halmahera Regency, at the base ofthe western peninsula of the island, but it was recordedprior to 1950 as far as the southern point of Halmahera.[6]More recent records showed that it is still present ina significantly larger area, including the northeast ofthe island,[14] and locals claim that it also occurs in theswamps near Kao, in the northwest.[6]

Sago palms

4 Behaviour

The difficult habitat and retiring nature of the invisi-ble rail mean that information on its lifestyle is sparse,and there are few confirmed sightings.[17] Recorded fooditems include sago shoots and insects. It also feeds at cutsago plants, although it is unclear whether it is eating thedecaying plant or searching for other edible items.[6] Itswallows small stones, as do all rails, to help break up itsfood in the gizzard.[18]

The invisible rail is thought to be monogamous, but littleelse is known of its courtship behaviour prior to nesting.A report of 4–5 striped chicks was long thought to beincorrect, since such a plumage is not normal for rails.[6]In this family, chicks are typically precocial, downy andblack, with any ornamentation confined to the head, bareflesh, or specially modified plume feathers.[19]

The issue was resolved in November 2010 when a nestwas found in the top of a rotting tree stump, 1 m (39 in)above ground level and 46 m (151 ft) in from the edgeof a dry swamp forest in Aketajawe-Lolobata NationalPark. The nest depression was 15 cm (5.9 in) in depth,with a lower layer of small wood chips at its base anda lining of dead leaves. The egg shells were brownish-white with dark brown and black markings of differentsizes. The two very young chicks were entirely coveredin black down, contrasting with a white pollux (the equiv-alent of the thumbnail on a human hand) and pink indexnail. The bill was black with a white tip, and the legs wereblack-streaked brown. The eyes had grey irises and blue

3

pupils. Rail chicks leave the nest soon after hatching, sothe chicks were assumed to be only a day or two old.[14]

5 Status

Bird species with a restricted range are especially vulner-able to human activities, and eight of the 26 bird speciesoccurring only in the “Northern Maluku Endemic BirdArea” are threatened, including the invisible rail.[6] Al-most a quarter of all rail species have conservation con-cerns, and flightless island species are particularly at risk,at least 15 species having become extinct since 1600.[20]The estimated population of the invisible rail is 3,500–15,000 birds,[17] and its restricted range and small pop-ulation mean that the species is classified as Vulnerableby the International Union for Conservation of Nature(IUCN),[1] although this rail is so poorly known that itmay be more common than the estimates suggest.[6]

Habitat loss has occurred through commercial harvest-ing of the sago,[6] or conversion to rice cultivation andfishponds.[1] The rail is a prized food for local peoplewho catch it with traps made from strings of bark andhunt it with dogs.[10] The only described nest was in anarea well-used by local villagers, and the rail may be moreadaptable to habitat changes than was previously thought.There were also several sightings in northeast Halmaherain 2008 and 2011, extending the area in which this birdhas been seen in recent years.[14]

6 References[1] BirdLife International (2012). "Habroptila wallacii".

IUCN Red List of Threatened Species. Version 2013.2.International Union for Conservation of Nature. Re-trieved 26 November 2013.

[2] Hoyo, Josep del; Elliott, Andrew; Sargatal, Jordi; Christie,David A; de Juana, Eduardo (eds.) (2013). “Rails,Gallinules and Coots”. Handbook of the Birds of theWorld Alive. Barcelona: Lynx Edicions. Retrieved 13April 2014. (subscription required)

[3] ἁβρός, πτίλον. Liddell, Henry George; Scott, Robert; AGreek–English Lexicon at the Perseus Project.

[4] Jobling, James A (2010). The Helm Dictionary of Scien-tific Bird Names. London: Christopher Helm. pp. 184,406. ISBN 978-1-4081-2501-4.

[5] de Haan, G A L (1950). “Notes on the Invisible FlightlessRail of Halmahera (Habroptila wallacii Gray)". Amster-dam Naturalist 1: 57–60.

[6] “Invisible Rail Habroptila wallacii" (PDF). Birdbase.Hokkaido Institute of Environmental Sciences. Retrieved17 June 2011.

[7] Olson, Storrs L (1973). “A classification of the Rallidae”(PDF).Wilson 85 (4): 381–416.

[8] Mees, G F (1982). “Birds from the lowlands of southernNew Guinea (Merauke and Koembe)". Zoologische Ver-handelingen 191: 1–188.

[9] Kirchman, Jeremy J (2012). “Speciation of FlightlessRails on Islands: A DNA-based phylogeny of the typ-ical rails of the Pacific”. The Auk 129 (1): 56–69.doi:10.1525/auk.2011.11096.

[10] Taylor & van Berlo (1998) pp. 451–452.

[11] Gray, George Robert (1860). “List of birds collected byMr. Wallace at the Molucca Islands, with descriptions ofnew species, &c”. Proceedings of the Zoological Societyof London 28: 365.

[12] Allen, Desmond; Oliveros, Carl; Española, Carmela;Broad, Genevieve; Gonzalez, Juan Carlos T (2004). “Anew species of Gallirallus from Calayan island, Philip-pines” (PDF). Forktail: Journal of Asian Ornithology 20:1–7. Retrieved 18 June 2011.

[13] Heinrich, Gerd (1956). “Biologische Aufzeichnun-gen über Vögel von Halmahera und Batjan”. Jour-nal für Ornithologie (in German) 97 (1): 31–40.doi:10.1007/BF01670833.

[14] Bashari, Hanom; van Balen, Bas (2011). “First breed-ing record of the Invisible Rail Habroptila wallacii".BirdingASIA 15: 20–22.

[15] Flach, Michiel (1997). Sago palm: Metroxylon saguRottb. Promoting the conservation and use of underuti-lized and neglected crops (PDF) 13. Gatersleben, Ger-many/Rome: Institute of Plant Genetics and Crop PlantResearch/International Plant Genetic Resources Institute.pp. 21–23. ISBN 978-92-9043-314-9.

[16] Collar, Nigel J (2009). “Pioneer of Asian ornithology:Gerd Heinrich” (PDF). BirdingASIA 11: 33–40.

[17] “Invisible Rail Habroptila wallacii". Species factsheet.BirdLife International. Retrieved 16 June 2011.

[18] Taylor & van Berlo (1998) p. 39.

[19] Krebs, Elizabeth A; Putland, David A (2004). “Chicchicks: the evolution of chick ornamentation inrails” (PDF). Behavioral Ecology 15 (6): 946–951.doi:10.1093/beheco/arh078.

[20] Taylor & van Berlo (1998) pp. 56–61.

7 Cited texts• Taylor, Barry; van Perlo, Ber (1998). Rails.Robertsbridge, East Sussex: Pica / ChristopherHelm. ISBN 1-873403-59-3.

8 External links• Drumming at xeno-cato• Six images of adult and chicks at Oriental Bird Im-ages

4 9 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

9 Text and image sources, contributors, and licenses

9.1 Text• Invisible rail Source: http://en.wikipedia.org/wiki/Invisible%20rail?oldid=654561236 Contributors: Shyamal, Jimfbleak, Wetman,DanielCD, Hesperian, Mendaliv, Eubot, Tony1, Crisco 1492, BirdValiant, Gyrobo, Snowmanradio, Ww2censor, Ohconfucius, IronGar-goyle, Makyen, Bruinfan12, J Milburn, Stavenn, Cydebot, Kuvlux, Casliber, Maias, DrKiernan, Frickeg, JohnBlackburne, TXiKiBoT,Luffy487, Thanatos666, GorillaWarfare, P. S. Burton, Frongle, Little Mountain 5, Addbot, Luckas-bot, Materialscientist, Resident Mario,I dream of horses, Moonraker, Gerda Arendt, Orenburg1, Innotata, Sarastro1, EmausBot, John of Reading, ZéroBot, AManWithNoPlan,Cheeseballs123, Jay-Sebastos, Регион102, Whoop whoop pull up, ClueBot NG, Prioryman, Michaelmas1957, BarkingMoon, BG19bot,Northamerica1000, AzseicsoK, EnzaiBot, Mr. Guye, RubyMurray, Skielheim, TFA Protector Bot, Habiana, Monkbot, Biblioworm, Naytz,Rubbish computer, Sambathl, Jett aplin, DrAwesome78139 and Anonymous: 19

9.2 Images• File:Commons-logo.svg Source: http://upload.wikimedia.org/wikipedia/en/4/4a/Commons-logo.svg License: ? Contributors: ? Originalartist: ?

• File:Eagle_01.svg Source: http://upload.wikimedia.org/wikipedia/commons/5/5c/Eagle_01.svg License: CC0 Contributors: ? Originalartist: ?

• File:Habroptila_wallacii_2012_Indonesia_stamp.jpg Source: http://upload.wikimedia.org/wikipedia/commons/e/ef/Habroptila_wallacii_2012_Indonesia_stamp.jpg License: Public domain Contributors: [1] Original artist: Unknown

• File:Habroptila_wallacii_halmahera_map.png Source: http://upload.wikimedia.org/wikipedia/commons/d/d5/Habroptila_wallacii_halmahera_map.png License: CC BY-SA 3.0 Contributors: Own work Original artist: Jimfbleak

• File:Sago_Palm_Trees_ESP_PNG.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/83/Sago_Palm_Trees_ESP_PNG.jpg License: CC-BY-SA-3.0 Contributors: Own work Original artist: Toksave

• File:Wikispecies-logo.svg Source: http://upload.wikimedia.org/wikipedia/commons/d/df/Wikispecies-logo.svg License: CC BY-SA 3.0Contributors: Image:Wikispecies-logo.jpg Original artist: (of code) cs:User:-xfi-

9.3 Content license• Creative Commons Attribution-Share Alike 3.0