Réunion Sacred Ibis

Réunion Sacred Ibis
Conservation status
Extinct (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Pelecaniformes
Family:	Threskiornithidae
Subfamily:	Threskiornithinae
Genus:	Threskiornis
Species:	†T. solitarius
Binomial name
†Threskiornis solitarius (de Sélys-Longchamps, 1848)
Synonyms
Borbonibis latipes Raphus solitarius Victoriornis imperialis

The Réunion Sacred Ibis, Threskiornis solitarius, is an extinct bird species that was native to the island of Réunion. It is probably the same bird discovered by Portuguese sailors there in 1613. Until recently assumed by biologists to have been a relative of the Dodo (Raphus cucullatus), it was thus classified as a member of the didine pigeons (subfamily Raphinae) and called the "Réunion Solitaire" (Raphus solitarius).

Description and ecolology

An extant relative of the same genus, the African Sacred Ibis Threskiornis aethiopicus

It had a white plumage, with black wingtips and tail, and a dark, naked head. Bill and legs were long, the former slim and slightly downcurved. All in all, it looked much like a small Sacred Ibis with short wings.

The Réunion Sacred Ibis lived solitarily in deep forests near freshwater, where it fed on invertebrates like worms and crustaceans which it caught or dug out of the mud with its long beak. If threatened, it is described to have tried to get away on foot, but using its wings for assistance and to glide short distances, especially downhill. The old vernacular name "Réunion Flightless Ibis" is thus misleading. Travellers' reports as well as bone measurements indicate that it was well on its way to flightlessness, but could still fly some distance on its own power after a running take-off.

The last account of the "Réunion Solitaire" was recorded in 1705, indicating that the species probably became extinct sometime early in that century.

17th century descriptions and paintings

The bird was at various times identified with 17th century descriptions and paintings of a white dodo-like bird, which did not match the descriptions of solitaries (reclusive non-gregarious large birds) seen by contemporary explorers on Réunion very well – apart from being mostly white. Due to this, some assumed two species (Raphus solitarius and Victoriornis imperialis) co-existed on Réunion (or "Bourbon", as it was called in former times) – one dodo-like, one resembling the Rodrigues Solitaire (Pezophaps solitaria). The latter was a dodo relative that generally was not a social bird but for breeding formed monogamous couples. These defended a territory around their large, easily recognized ground nest, deep in the woods; they were thus said to have a "solitary" lifestyle. Though the same French word was used for the birds of both Rodrigues and Réunion, the Réunion Solitaire was given this name because only single individuals were usually encountered all year round. Similar nesting behaviour as on Rodrigues (in the Réunion bird, or in the dodo for that matter) was never reported, marking a conspicuous difference between the two species.

The bird was first described as follows by Mr. Tatton, the Chief Officer of Captain Castleton:

There is store of land fowle both small and great, plenty of Doves, great Parrats, and such like ; and a great fowle of the bignesse of a Turkie, very fat, and so short winged, that they cannot fly, being white, and in a manner tame: and so be all other fowles, as having not been troubled nor feared with shot. Our men did beat them down with sticks and stones. Ten men may take fowle enough to serve fortie men a day.

And as follows by Sieur D. B. (Dubois) in 1674:

Solitaires. These birds are thus named because they always go alone. They are as big as a big goose and have white plumage, black at the extremity of the wings and of the tail. At the tail there are some feathers resembling those of the Ostrich. They have the neck long and the beak formed like that of the Woodcocks, but larger, and the legs and feet like those of Turkey-chicks. This bird betakes itself to running, only flying but very little. It is the best game on the Island.

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

Walter Rothschild assumed these descriptions where of the white dodo as seen in the painting by Pieter Withoos, but that the specimen might have been albinistic, due to the wing tips being yellow instead of black as in the old descriptions.^[1]

Pieter Withoos's painting of a white dodo along with 17th century descriptions of white turkey sized birds were used by 19th century naturalists to show that a white dodo had lived on Réunion

It appears that most depictions of white dodos were based on a 1611 painting of a whitish specimen from Rudolf II's collection by Roelant Savery, which was later copied in paintings by Pieter Holsteyn and Pieter Withoos.^[2] A walghvogel described as having a "dirty off-white coloring" was mentioned in an inventory of specimens in the Holy Roman Emperor Rudolf II's collection in Prague by David Fröschl in 1607-1611, so if the 1611 painting by Savery, who was contracted to Rudolf II at the time, is based on this specimen, it could not have been from Reunión, which was not visited by Europeans until 1635.^[3]

Subfossil remains

Borbonibis latipes was described from the first ibis bones found on Réunion, before a connection to the solitaire reports had been made. The epithet solitarius derives from the Raphus solitarius description of Baron Edmund de Sélys-Longchamps in 1848, but that the solitare reported from Réunion actually existed was not confirmed until the discovery of bones on Réunion in the late 20th century.

The discovery that it actually was an ibis perfectly fits what the early travellers said about its plumage and habits. The confusion can be explained by the fact that solitaire was used by the writers of the descriptions as a term indicating a non-gregarious lifestyle, which the ibis happened to share with the Rodrigues Solitaire, but was interpreted by the scientists as an indication of a taxonomic relationship.

References

1. ^ http://www.archive.org/download/extinctbirdsatte00roth/extinctbirdsatte00roth.pdf
2. ^ http://julianhume.co.uk/wp-content/uploads/2010/07/Hume-and-Cheke-no-illustrations.pdf
3. ^ http://julianhume.co.uk/wp-content/uploads/2010/07/new-discoveries.pdf

• BirdLife International (2004). Threskiornis solitarius. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 11 May 2006. Database entry includes justification for why this species is listed as extinct
• Avian web on the Réunion Sacred Ibis (same text, but with a picture)
• The extinction website