Rodrigues rail

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Rodrigues rail
An illustration of bird bones, mostly laid out in vertical rows
Subfossil bones described in 1879, including two skulls, a pelvis
, and limb bones

Extinct (mid-18th century)  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Gruiformes
Family: Rallidae
Genus: †Erythromachus
Milne-Edwards, 1874
Species:
†E. leguati
Binomial name
†Erythromachus leguati
Milne-Edwards, 1874
A map showing the location of Rodrigues, an island east of Madagascar in the Indian Ocean
Location of Rodrigues
Synonyms
List
  • Aphanapteryx leguati Günther & Newton, 1879
  • Miserythrus leguati Newton, 1874
  • Erythromachus leguata Fürbringer, 1888 (lapsus)
  • Aphanopteryx leguati Rothschild, 1907 (lapsus)
  • Myserythrus leguati Hachisuka, 1953 (lapsus)
  • Erthyromachus leguati Brodkorb, 1967 (lapsus)

The Rodrigues rail (Erythromachus leguati), also known as Leguat's gelinote or Leguat's rail, is an

Subfossil remains were later discovered and correlated with the old accounts in 1874, and the species was named E. leguati in Leguat's honour. It is generally kept in its own genus, Erythromachus, but has sometimes been assigned to the genus Aphanapteryx along with its close relative the red rail (A. bonasia) of Mauritius
; their relationship with other rails is unclear.

The Rodrigues rail was about 35 cm (14 in) long and weighed at least 500 g (18 oz). It was described as having grey plumage, a red beak, red legs, and a naked red patch around the eye. The beak was long and curved downwards. It was

flightless
and fed on tortoise eggs. It was described as being attracted to red objects, which humans exploited while hunting it. The Rodrigues rail is believed to have become extinct in the mid-18th century mainly because of predation by introduced cats and hunting.

Taxonomy

In 1848, the English

Sir Thomas Herbert, which he thought related. Strickland also noted similarities with a bird from Mauritius, which would later be identified as the red rail (Aphanapteryx bonasia).[2][5]

An illustration of bird bones laid out in rows
First bones described in 1874; a tarsometatarsus (1.–1e.), a fragmentary skull (3.–3b., and a sternum (4.–4c.)

In 1874, the French zoologist

subfossil bird bones from Rodrigues he had received via the British ornithologist Alfred Newton, which had been excavated under the supervision of his brother, Colonial Secretary Edward Newton.[6][7] Milne-Edwards connected Leguat's account with three bones (a sternum, a tarsometatarsus, and a fragmentary skull) found in caves of the Plaine Corail region, Rodrigues. He recognised their similarity to those of the red rail, while noting it supposedly had a straighter beak (as described by Leguat). Milne-Edwards coined the generic name Erythromachus from the Greek words eruthros, "red", and makhç, "battle" (also translated as "hostile to red"), in reference to its attraction to red objects, and the specific name is in honour of Leguat.[6][5][8]

The name Erythromachus was incorrectly explained as referring to the

syntype series was later listed from specimens there, presumably by A. Newton.[8]

In 1875, A. Newton also identified a reference to the bird in the 1725–26 account of the French traveller Julien Tafforet, Relation de l'Ile Rodrigue, which had recently been rediscovered.

rail, and also noted that some specimens had beaks as curved as that of the red rail.[11] In 1921, the American linguist Geoffroy Atkinson questioned the bird's existence, in an article that doubted the veracity of Leguat's memoir.[12] The American ornithologist James Greenway suggested in 1967 that Leguat's description referred to wind-blown purple swamphens, since the word grey is sometimes used synonymously with blue in old descriptions.[13] This idea has not been accepted by other commentators.[3] Today, it is widely accepted that Leguat's memoirs represent credible observations of local birds in life.[14] His observations on the local fauna are considered some of the first cohesive accounts of animal behaviour in the wild.[15]

In 1999, the French

palaeontologist Cécile Mourer-Chauviré and colleagues pointed out that a carpometacarpus bone assigned to the Rodrigues rail and illustrated by Günther and E. Newton in 1879 does not belong to a rail, and therefore not this bird.[16] More subfossils have since been discovered, including an associated but incomplete skeleton with a complete skull and jaws found in Caverne Poule Rouge in 2005.[17][18]

Evolution

painting of red rail
Painting of the similar red rail, by Hoefnagel, ca. 1610

Apart from being a close relative to the red rail, the relationships of the Rodrigues rail are uncertain and the two are commonly listed as separate genera, Aphanapteryx and Erythromachus, but have

loss of flight rather than common descent. He also suggested that the grouping of the Rodrigues and red rail into the same genus may have been influenced by their geographical distribution.[19] Mourer-Chauviré and colleagues also considered the two as belonging to separate genera.[16]

Rails have reached many oceanic

flightlessness. According to the British researchers Anthony S. Cheke and Julian P. Hume in 2008, the fact that the red rail lost much of its feather structure indicates it was isolated for a long time. These rails may be of Asian origin, like many other Mascarene birds.[15] In 2019, Hume supported the distinction of the two genera, and cited the relation between the extinct Mauritius scops owl and the Rodrigues scops owl as another example of the diverging evolutionary paths on these islands. He stated that the relationships of the Rodrigues and red rails was more unclear than that of other extinct Mascarene rails, with many of their distinct features being related to flightlessness and modifications to their jaws due to their diet, suggesting a long period of isolation. He suggested their ancestors could have arrived on the Mascarenes during the middle Miocene at the earliest, but it may have happened more recently. The speed with which these features evolved may also have been affected by gene flow, resource availability, and climate events. Flightlessness can evolve rapidly in rails, sometimes repeatedly within the same groups, as in Dryolimnas, so the distinctness of the Rodrigues and red rails may not have taken long to evolve; some other specialised rails evolved in less than 1–3 million years. Hume suggested that the two rails were probably related to Dryolimnas, but their considerably different morphology made it difficult to establish how. In general, rails are adept at colonising islands, and can become flightless within a few generations in environments without predators, yet this also makes them vulnerable to human activities.[8]

Description

An illustration of a bird with a long neck, a long, sharp, red beak, red legs and feet, mid-grey to black feathers and a large, red, naked area around its eye
Frohawk's 1907 restoration, based on an old outline illustration and a description. Olson considered the image "rather fanciful"[5]

The Rodrigues rail was about 35 cm (14 in) long, smaller than the red rail, but with proportionally longer wings. It may have weighed at least 500 g (18 oz).

cranium of the Rodrigues rail was slightly elongated, convex in every direction, and compressed from top to bottom in side-view. The cranium was medium-sized among Mascarene rails, 38 mm (1.5 in) long and 20 mm (0.79 in) wide. It had a narrow, long frontal region, 6.5 mm (0.26 in) at its least width.[11][15][17][8]

The beak was long and curved downwards as in the red rail, but the narial openings were longer. The

foramina (openings) on the upper bill, which did not extend to the front edge of the narial opening. The mandible was long and narrow, ending in a sharp point, with the length of the mandibular symphysis (the area where the halves of the mandible meet) being about 65% of the cranium's length. The mandible had large, deep set foramina, which ran almost up to a deep sulcus (furrow) at the centre of the mandible.[11][8] Günther and Newton stated that the examined beaks varied greatly in size and shape; some specimens had short and almost straight beaks, while others had much longer beaks (up to one third longer) that were prominently curved. These writers were unsure whether this was related to the overall size of an individual bird or to sexual dimorphism.[11] Livezy was unable to confirm the idea that the differences in the beaks reflected dimorphism in 2003, but thought it probable.[20] Hume examined all available upper beaks in 2019, but found no differences in curvature.[8]

The bones associated with the forelimbs were generally small in proportion to the bird. The

neotenic, with juvenile features such as weak pectoral apparatuses and downy plumage.[22][20]

Contemporary accounts

A line drawing of two flightless birds, each with an ovoid body, long neck and pointed beak
Schlegel's 1854 outlines of "dodo" species (the second supposedly from Rodrigues), which were actually red rails seen by travellers on Mauritius

The Rodrigues rail was first recorded by Leguat in his 1708 memoir, and his account of the bird reads as follows:

Our 'gelinotes' are fat all the year round and of a most delicate taste. Their colour is always of a bright grey, and there is very little difference in plumage between the two sexes. They hide their nests so well that we could not find them out, and consequently did not taste their eggs. They have a red naked area round their eyes, their beaks are straight and pointed, near two and two-fifths inches long, and red also. They cannot fly, their fat makes them too heavy for it. If you offer them anything red, they are so angry they will fly at you to catch it out of your hand, and in the heat of the combat we had an opportunity to take them with ease.[23]

Tafforet's 25-1726 description of the bird's appearance and behaviour reads as follows:

There is another kind of bird, the size of a young hen, which has the beak and legs red. Its beak is roughly like that of a curlew, except that it is a little deeper and not quite so long. Its plumage is mottled with white and grey. They generally feed on the eggs of the land tortoises, which they take from the ground, and makes them so fat that they often have difficulty running. They are very good to eat, and their fat is of a yellowish-red, which is excellent for pains. They have small pinions [wings], without feathers, so they cannot fly; but on the contrary, they run very well. Their cry is a continual whistling. When they see somebody pursuing them they produce another sort of noise from their bodies, like that of a person who has hiccups and with the stomach tensed.[8]

Unlike the red rail and many other extinct Mascarene birds, the Rodrigues rail was not illustrated by contemporaneous artists. Olson described reconstructions made for the British zoologist

Extinct Birds and the Japanese ornithologist Masauji Hachisuka's 1953 book The Dodo and Kindred Birds as "rather fanciful". The English artist Frederick William Frohawk based his restoration in the former book on an outline illustration, which was in turn based on a sketch drawn by Herbert, which is now known to depict the red rail.[5][23] The German zoologist Hermann Schlegel thought it depicted a species of dodo (which he called Didus herbertii) from Rodrigues when he drew the outline in 1854, and that it was the species mentioned by Leguat.[24]

Behaviour and ecology

Leguat's 1708 memoir
, showing his settlement on Rodrigues, with tortoises and rats below

According to Tafforet's account, the Rodrigues rail fed on the eggs of the now extinct

Kontikia whartoni and the now extinct Geonemertes rodericana, by probing leaf-litter or rotting wood.[8] Sexual dimorphism may have reflected differences in diet between the sexes.[15]

Since Leguat was unable to locate its nests, the Rodrigues rail may have nested outside the easily accessible open forest as was typical in coastal and lowland areas, and rather nested deep in forested valleys or mountainous hills of the interior, according to Hume. Its nests may have been well concealed in vegetation on the ground, as is the case of other flightless rails.[15] Like the red rail, it was said to be attracted to the colour red, but the significance of this is unknown.[3] This behaviour led Hume to call it an "aggressive species".[8] According to Milne-Edwards, the bird had legs "made for running".[23]

Many other species endemic to Rodrigues became extinct after humans arrived, and the island's ecosystem was heavily damaged. Before humans arrived, forests covered the island entirely, but very little of those remain today. The Rodrigues rail lived alongside other recently extinct birds, such as the Rodrigues solitaire, the Rodrigues parrot, Newton's parakeet, the Rodrigues starling, the Rodrigues scops owl, the Rodrigues night heron, and the Rodrigues pigeon. Extinct reptiles include the domed Rodrigues giant tortoise, the saddle-backed Rodrigues giant tortoise, and the Rodrigues day gecko.[15]

Extinction

Map of Rodrigues, decorated with solitaires
Map of human settlement on Rodrigues
Leguat's 1708 maps of Rodrigues and his settlement.

Many terrestrial rails are flightless, and island populations are particularly vulnerable to man-made changes; as a result, rails have suffered more extinctions than any other family of birds. All six endemic species of Mascarene rails are extinct, caused by human activities. For at least a century the Rodrigues rail may have coexisted with rats, which were perhaps introduced by a group of sailors from a Dutch ship marooned there in 1644. Though rats were well established and numerous by the time Leguat and Tafforet stayed on the island, the rails also remained common, perhaps due to their aggressive nature.[8]

In 1763, the French astronomer

1761 transit of Venus
:

I heard said of neither gélinottes [Rodrigues rail], nor butors [Rodrigues night heron], nor alouettes [small waders], nor bécassines [shearwaters or petrels]; there may have been some at the time of François Leguat, but they have either retreated from their homes or, more likely, the races no longer survive, since the island has been populated with cats.[8]

The French began settling Rodrigues in 1735 (to supply Mauritius with tortoise meat), and Hume and the British ornithologist Michael Walters stated in 2012 that this must have taken a toll on the rails through hunting and deforestation, but their rapid disappearance was probably caused by cats introduced to control the rats around 1750, and the species may have gone extinct within a decade.[10][8] Cheke responded in 2013 that there was no deforestation at the time, the species appears to have survived the rats, and that cats were the main culprits, assisted by hunting.[25]

References

  1. doi:10.2305/IUCN.UK.2016-3.RLTS.T22728889A94999834.en
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  2. ^
    S2CID 52124404. Archived
    from the original on 13 August 2017. Retrieved 1 October 2017.
  3. ^
    ISBN 978-0-8014-3954-4
    .
  4. ^ Leguat, F. (1891). Oliver, S. P. (ed.). The voyage of François Leguat of Bresse, to Rodriguez, Mauritius, Java, and the Cape of Good Hope. Vol. 1. London: Hakluyt Society. p. 81. Archived from the original on 11 April 2016. Retrieved 1 October 2017.
  5. ^
    ISBN 978-0-87474-804-8
    .
  6. ^ a b Milne-Edwards, A. (1866–1874). Recherches sur la faune ornithologique éteinte des iles Mascareignes et de Madagascar (in French). Paris: G. Masson. pp. 122–123. Archived from the original on 10 October 2016. Retrieved 1 October 2017.
  7. S2CID 128901896
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  8. ^
    S2CID 198258434
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  9. ^ Newton, A. (1875). "Additional evidence as to the original fauna of Rodriguez". Proceedings of the Zoological Society of London. 1875: 39–43. Archived from the original on 2 October 2017. Retrieved 13 January 2018.
  10. ^
    ISBN 978-1-4081-5725-1
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  11. ^
    doi:10.1098/rstl.1879.0043. Archived
    from the original on 21 March 2016. Retrieved 2 September 2015.
  12. S2CID 163478864
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  13. ISBN 978-0-486-21869-4
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  14. ISBN 978-0-00-714572-0
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  15. ^
    ISBN 978-0-7136-6544-4
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  16. ^
    hdl:10088/2005
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  17. ^ a b Hume, J. P. (2013). Göhlich, U. B.; Kroh, A. (eds.). "A synopsis of the pre-human avifauna of the Mascarene Islands" (PDF). Proceedings of the 8th International Meeting of Society of Avian Paleontology and Evolution: 195–237. Archived (PDF) from the original on 3 March 2016. Retrieved 15 October 2017.
  18. ISBN 9780511735769.{{cite book}}: CS1 maint: location missing publisher (link
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  20. ^
    JSTOR 40168337
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  21. doi:10.1111/j.1469-7998.1893.tb00001.x. Archived
    from the original on 11 September 2017. Retrieved 13 January 2018.
  22. ^ Herremans, M. Trends in the evolution of insular land birds, exemplified by the Comoros, Seychelles and Mascarenes. Proceedings International Symposium on Vertebrate Biogeography and Systematics in the Tropics. Bonn. pp. 249–260.
  23. ^ a b c Rothschild, W. (1907). Extinct Birds. London: Hutchinson & Co. p. 135. Archived from the original on 9 May 2018. Retrieved 31 July 2014.
  24. ^ Schlegel, H. (1854), "Ook een Woordje over den Dodo (Didus ineptus) en zijne Verwanten", Verslagen en Mededeelingen der Koninklijke Akademie van Wetenschappen (in Dutch), 2: 232–256
  25. ^ Cheke, A. S. (2013). "Extinct birds of the Mascarenes and Seychelles – a review of the causes of extinction in the light of an important new publication on extinct birds". Phelsuma. 21: 4–19.

External links

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