Réunionibis

The Reunion Ibis (Threskiornis solitarius) is an extinct species of ibis that was endemic to the island of Réunion, east of Madagascar in the Indian Ocean.

Systematik

In the 19th century, accounts from the 17th and 18th centuries describing white "Solitaire" birds on Reunion were assumed to refer to white relatives of the Dodo, due to one account specifically mentioning Dodos, and because 17th century paintings of white Dodos had recently surfaced. The "Reunion Solitaire" was thus classified as a member of the pigeons (subfamily Raphidae) and called Raphus solitarius. No Dodo-like fossils were ever found on Reunion, so it was later questioned whether the white Dodo paintings had anything to do with the island. In the late 20th century, the discovery of a subfossil ibis lead to the idea that the accounts actually referred to this species. The ibis was classified as a member of the genus Threskiornis, of which it is the only known extinct species.

Identification and taxonomy

Pieter Withoos's painting of a white Dodo among various birds

The supposed "White Dodo" of Réunion is now believed to have been an erroneous conjecture based on contemporary reports of the Réunion Sacred Ibis, combined with paintings by Pieter Withoos and Pieter Holsteyn from the 1600s of white Dodos that surfaced in the 19th century.

Willem Ysbrandtszoon Bontekoe, who visited Réunion around 1619, mentioned that it was inhabited by "Dod-eersen", though without mentioning colouration: Vorlage:Quotation When his journal was published in 1646, it was accompanied by a copy of Roelant Savery's "Crocker Art Gallery sketch".

Chief Officer J. Tatton was the first to mention a specifically white bird on Réunion in 1625. M. Carre of the French East Indies Company described the behaviour of the bird in 1699, explaining the reason for the name "Solitaire":

Vorlage:Quotation Baron Edmund de Sélys-Longchamps coined the name Raphus solitarius for these birds in 1848, as he believed the accounts referred to a species of Dodo. When 17th century paintings of white Dodos were discovered by 19th century naturalists, it was assumed they depicted these birds. Walter Rothschild suggested that the reason the painted specimens had yellow wing-tips instead of black as in the old descriptions might have been albinism. It was also suggested that differences in paintings were due to sexual dimorphism. Others believed it was a species similar to the Rodrigues Solitaire, as it was referred to by the same name, or even that there were white species of both the Dodo and Solitaire on the island. Rothschild used the name Didus solitarius for the Solitaire in his 1907 book Extinct Birds, even though this binomial was a junior synonym preoccupied by the Rodrigues Solitaire.

Modern interpretation

Pieter Holsteyn's 1663 painting of a white dodo which was based on a 1611 painting by Roelant Savery

The Pieter Withoos painting, which was discovered first, appears based on an earlier painting by Pieter Holsteyn, three versions of which are known to have existed. According to Julian Hume and Anthony Cheke, it appears that all depictions of white Dodos were based on a single painting or copies of it, showing a whitish specimen, made by Roelant Savery in ca. 1611 called "Landscape with Orpheus and the animals". This was apparently based on a stuffed specimen then in Prague; a walghvogel described as having a "dirty off-white colouring" was mentioned in an inventory of specimens in the Prague collection of the Holy Roman Emperor Rudolf II to whom Savery was contracted at the time (1607–1611). Savery's several later images all show grayish birds, possibly because he had by then seen another specimen. It has also been suggested that the light plumage was a juvenile trait, a result of bleaching of old taxidermied specimens, or simply due to artistic license. Since Réunion was not visited by Europeans until 1635, the 1611 painting could not have shown a bird from there.

Until recently, only a few researchers doubted the connection between the Solitaire accounts and the Dodo paintings. They cautioned that no conclusions could be made without solid evidence such as fossils, and that nothing indicated the paintings had anything to do with Reunion. Robert W. Storer went as far as predicting that if any such remains were found, they would not belong to raphidae, or even columbidae.

In 1987, fossils of a recently extinct species of ibis from Réunion with a relatively short beak, Borbonibis latipes, were described, before a connection to the Solitaire reports had been made. Anthony Cheke suggested to one of the authors, Francois Moutou, that the fossils may have been of the Réunion Solitaire, and this suggestion was published in 1995. The ibis was also reassigned to the genus Threskiornis, now combined with the specific epithet solitarius from the binomial Raphus solitarius. Morphological study showed its closest relatives are the African Sacred Ibis (T. aethiopicus) of Africa and the Straw-necked Ibis (T. spinicollis) of Australia. The African Sacred Ibis also has similar coloured plumage to that described in the old descriptions of the Réunion Solitaire. No fossil remains of Dodo-like birds have ever been found on the island. Errol Fuller agrees the 17th century paintings do not depict Reunion birds, but has questioned whether the ibis fossils are necessarily connected to the "Solitaire" accounts. He notes that no evidence indicates the fossil ibis survived until the time Europeans reached Reunion.

Description

A close extant relative, the African Sacred Ibis

Contemporary accounts described the "Solitaire" as having white and grey plumage, with black wing tips and tail, a long neck and legs, and limited flight capabilities. Sieur D. B. Dubois' 1674 account is the most detailed description of the bird:

The plumage colouration mentioned is similar to that of the African Sacred Ibis and the Straw-necked Ibis, which are also mainly white and glossy black. The ornamental feathers on the back and wing tips of the extant African Sacred Ibis look similar to the feathers of an ostrich in the reproductive season, which echoes Dubois' description. Likewise, a fossil upper jaw found in 1994 showed that the bill of the Reunion Ibis was short and straight for an ibis, which corresponds with Dubois' Woodcock comparison.

The known fossils of the Reunion Ibis show that it was more robust, likely much heavier, and had a larger head than other members of its genus. Rough protuberances in the wing bones are similar to those of birds that use their wings in combat. It was perhaps flightless, but this has not left significant osteological traces; no complete skeletons have been collected, but of the known pectoral elements, only one feature indicates reduction in flight capability. The coracoid is elongated and the radius and ulna are robust, as in flighted birds, but a particular foramen between a metacarpal and the alular is otherwise only known from flightless birds, such as some ratites, penguins, and several extinct species. As contemporary accounts are inconsistent on whether the Solitaire was flightless or had some flight capability, Mourer-Chauvire suggested that this was dependent on fat-cycles; it was described as being "fat", so perhaps it could not fly when it was fat, but could when it was thin.

Behaviour and ecology

The Straw-necked Ibis, another close relative

The Reunion Ibis lived in the forest and and was termed a land-bird by Dubois, so it did not live in typical ibis habitats such as wetlands. It has been proposed that this is because the ancestors of the bird colonised Reunion before swamps had developed, and had therefore became irreversibly adapted to the habitats present at that time. They were perhaps prevented from colonising Mauritius as well due to the presence of Red Rails there, which may have occupied a similar niche. It appears it lived in high altitudes, and perhaps had a limited distribution.

The only mention of its diet and exact habitat is Feuilley's account from 1708, which is also the last record of the bird:

Vorlage:Quotation The diet and mode of obtaining it matches that of an ibis, whereas members of the raphidae are known to have been frugivorous.

Accounts by early visitors indicate the Solitaire was found near their landing sites, but they were found only in remote places by 1667. The bird may have survived in eastern lowlands until the 1670s. Though many late 1600s accounts state the Solitaire was good food, Feuilley stated the bird tasted bad. This may be because the bird changed its diet when it moved to more rugged, higher terrain, to escape pigs that destroyed their nests; since it had limited flight capabilities, it likely nested on the ground.

Many other of the endemic species of Reunion became extinct after the arrival of man, so the ecosystem of the island is heavily damaged. Before humans arrived, forests covered the island entirely, but very little remains today due to deforestation. The Reunion Ibis lived alongside other recently extinct birds such as the Hoopoe Starling, the Mascarene Parrot, the Réunion Parakeet, the Réunion Swamphen, the Réunion Owl, the Réunion Night Heron, and the Réunion Pink Pigeon. Extinct reptiles include the Réunion giant tortoise and the Mauritian giant skink. The Small Mauritian Flying Fox and the snail Tropidophora carinata lived on Réunion and Mauritius, but vanished from both islands.

Extinction

Forested mountain tops on inland Reunion

As Reunion was populated, the Reunion Ibis appears to have become confined to the tops of mountains. Introduced predators such as cats and rats had an impact on the ibis. Over hunting also contributed, and several contemporary accounts state the bird was hunted for food in large numbers.

in 1625, J. Tatton described the tameness of the Solitaires and how easy it was to hunt, as well as the large quantity consumed: Vorlage:Quotation

Restoration of the Reunion Solitaire by Frederick William Frohawk, a hybrid between Dubois' account and the Rodrigues Solitaire

In 1671, Melet described the slaughter of several types of birds on the island, and mentioned the culinary quality of the Solitaire: Vorlage:Quotation

The last definite account of the "Reunion Solitaire" was Feuilley's from 1708, indicating that the species probably became extinct sometime early in the century. In the 1820s, Louis Henri de Freycinet asked an old slave about drontes (old Dutch word for Dodo), and was told the bird existed around Saint-Joseph when his father was an infant. This would perhaps be around 1710-15, but the account may be unreliable. Anthony Cheke and Julian Hume suspect that feral cats turned to higher inland areas, which were unreachable by pigs, once they had wiped out the wildlife in the lowlands. The ibis would then had been exterminated around 1710-15.

No specimens of the bird were ever collected. Carré attempted to send two solitaires to the royal menagerie in France, but they never arrived, as they refused to eat or drink. It has been claimed that Bertrand-François Mahé de La Bourdonnais sent a "Solitaire" to France from Réunion around 1740. Since the Réunion Ibis is believed to have gone extinct by this date, the bird may actually have been a Rodrigues Solitaire.

External links

Wikispecies: Threskiornis solitarius – Artenverzeichnis

• The Dodo – The merging of myth and reality: Half hour video interview with expert Julian Hume about the white Dodo