Mascarene teal
The Mascarene teal, also known as the Mauritius duck and Sauzier's teal, is an extinct species of duck that lived on the Mascarene Islands of Mauritius and Réunion. A small duck was mentioned in 17th century accounts from these islands which is thought to be this species, and it may also be depicted in one illustration. In 1893, various bones from the Mare aux Songes swamp of Mauritius were used to name a new species in the duck genus Anas, A. theodori, after who directed the excavations. Additional remains from Réunion were considered to belong to the same species in 1999, and it was determined to be related to the Sunda teal of the Indian Ocean.
The Mascarene teal was a small duck; in comparison with the extant ducks of Madagascar, it was larger than Bernier's teal, but smaller than Meller's duck. While overall most similar to the Sunda teal, the two differ in details of the sternum and lower leg bones. One contemporary account described the bird as "grey". Based on the proportions of its limb-bones, it had normal flight capabilities and was able to fly between Mauritius and Réunion, explaining how it occurred on both islands. It possibly nested in tree holes similar to related teals. The species was listed among the favourite prey of hunters; while abundant in 1681, it declined quickly thereafter, becoming extinct on Mauritius around 1700 and on Réunion a decade later. It was probably driven to extinction due to overhunting and predation by introduced animals, particularly cats.
Taxonomy
A few inadequate accounts mentioned a small duck on the Mascarene Islands of Mauritius and Réunion in the 17th century. In 1889, the Mauritius government requested exploration of the Mare aux Songes swamp for "historical souvenirs", where vast amounts of dodo remains had earlier been found. The new excavations, under the direction of the French naturalist, were successful, and apart from dodo bones, subfossil remains of other extinct animals, previously known as well as new species, were found. These bones were sent to the Cambridge Museum, where they were examined and described by the British ornithologist Edward Newton and the German ornithologist Hans Gadow in 1893. Based on the front part of a sternum, a pair of coracoids, eight humeri, and a pair of tarsometatarsi in bad condition, they determined the existence of a duck differing from those of Madagascar while being similar to Meller's duck of that island, but smaller. They named it as a new species in the duck genus Anas, A. theodori, in honour of Sauzier.In 1987, the British ornithologist Graham S. Cowles reported a hitherto undescribed skull of a duck from the collection of Louis Étienne Thirioux, an amateur naturalist from Mauritius. As it differed from any other extant ducks from the island, it was suggested to be the first known skull of the species described by Newton and Gadow. In the same publication, the British ecologist Anthony S. Cheke suggested that a 1674 mention of ducks on Réunion by the French traveller Sieur Dubois could refer to this species, though the garganey also regularly visits the island in small numbers. He also pointed out that two reports mention sarcelles and canards in addition to geese on Réunion, which may indicate there were two species of duck. The British ornithologist Hywel Glyn Young stated in 1996 that the exact relations of the species was uncertain, though it could be a southern teal or a mallard.
In 1999, the French palaeontologist Cécile Mourer-Chauviré and colleagues reported the front part of a sternum, an ulna, and a tibiotarsus from the Marais de l’Ermitage swamp on Réunion. By comparing these with bones of the Mascarene teal held in the National Museum of Natural History in France, which include a coracoid, four humeri, an incomplete juvenile carpometacarpus, a tibiotarsus, and two juvenile tarsometatarsi, they assigned the Réunion bones to the Mascarene teal, since the tibiotarsi were identical. By comparing the known bones of the Mascarene teal with those of other ducks, Mourer-Chauviré and colleagues found it to be most similar to the Sunda teal from the East and North East of the Indian Ocean, while larger and smaller than the extant ducks of Madagascar, Bernier's teal and Meller's duck, respectively.
Mourer-Chauviré and colleagues noted that Réunion lacks the kinds of distinctive flightless birds found on Mauritius such as the dodo, and that since Réunion is three million years old, this would be long enough for birds to lose their flight ability to the extent that it can be detected in their skeletons. They suggested that though members of the same birds groups initially colonised both Mauritius and Réunion, many of them evolving flightlessness, these species disappeared from Réunion due to volcanic eruptions of Piton des Neiges between 300,000 and 180,000 years ago. Thereafter the island would have been recolonised by flighted species like Mascarene teals from Mauritius, with none of them having time to become flightless since. They also reported two anatid carpometacarpi from Réunion that differed from those of Anas, but were similar to those of Aythya.
In 2008, Cheke and the British palaeontologist Julian P. Hume noted that while the Mascarene teal was similar to both the Sunda teal and Bernier's teal, the latter is brown, while one description indicates the Mascarene species was grey like the Sunda species; these species belong to a group called "grey teals", indicating dispersal from the east. Several of these types were previously thought to be races of the Sunda teal, but are now considered full species. Cheke and Hume raised the possibility that the Sunda teal bones Mourer-Chauviré and colleagues compared with the Mascarene teal actually belonged to the Australian grey teal. These writers suggested the ambiguous account of two kinds of ducks on Réunion could be explained by the possible Aythya remains, which they considered similar enough to the extant Madagascar pochard that it could be that species.
Description
The Mascarene teal was a small duck, and in comparison with the extant ducks of Madagascar, it was larger than Bernier's teal but smaller than Meller's duck. Based on the known bones, the sternum was wide and deep, the coracoid long, the humerus long, the ulna long, the tibiotarsus long, and the tarsometatarsus long.While overall most similar to the Sunda teal, the Mascarene teal differs in that the carina of the sternum projects further forwards, and the lower manubrial spine is narrow and elongated in the Sunda teal, and more elongated than in the Mascarene teal. The coracoid of the Mascarene teal is very similar to that of the Sunda teal. They both share a small, upwards directed spike on the internal side of the coracoid's hind surface, followed by a small depression. On the coracoid's front surface, near the acrocoracoid's internal side, there is an almost circular muscle scar in both species.
The humeri of the Mascarene and Sunda teal look very similar, with the humeral head forming a well-developed rim over the tricipital fossa, with a well-developed and elongated pectoral attachment. The ulna of the Mascarene teal is, like that of the Sunda teal, short and stout, and is the same size as in the male of the extant species. The humero-ulnar depression is pronounced at the ulna's upper end. As in the Sunda teal, the external condyle on the lower end of the ulna extends by a narrow, well-defined lip, which rises up along the shaft. Compared to those of the Sunda teal, the tibiotarsus and tarsometatarsus are longer and more robust in the Mascarene teal, and their upper and lower parts are wider, but the proportions of these and the coracoid are very close overall between the species.
Contemporary records
The 1681 ship's log of the British President mentioned gray teals on Mauritius, the only account that described its appearance:Cheke and Hume suggested in 2008 that "no ducks" was in reference to large, meaty ducks, unlike the small teal. The only contemporary mention of small anatids from Réunion is Dubois's from 1674:
In 2001, Cheke attempted to identify bird species on a 1670 illustration of a Dutch farm at Foul Bay, Mauritius, which showed agricultural practices and various animals. Cheke was primarily concerned with identifying a bird that had previously been suggested to be a dodo, which he instead considered a Mauritius sheldgoose. He found the other birds more enigmatic; he identified a crow-like bird as the extant Mauritius bulbul, and suggested two other waterbirds depicted in a stream could be cormorants or ducks. He noted that no visitors had mentioned living cormorants, while the Mascarene teal was still abundant at the time.
Behaviour and ecology
Mourer-Chauviré and colleagues stated in 1999 that the proportions of the Mascarene teal's limb-bones are very similar to those of the Sunda teal, indicating no reduction in flight capability, and are very different from those of flightless species like the Auckland teal and the Amsterdam wigeon. It is possible that the Mascarene teal had normal flight capabilities and was able to fly between Mauritius and Réunion, explaining how it occurred on both islands. Hume and the British ornithologist Michael Walters added in 2012 that it may also have moved seasonally. Cheke and Hume suggested in 2008 that, like the related Bernier's and Indo-Australasian teals, the Mascarene teal possibly nested in tree holes, as did the local starlings and parrots.Many other endemic species of Mauritius and Réunion were lost after the arrival of humans, so that the ecosystems of these islands are severely damaged and hard to conserve. Before humans arrived, the islands were entirely covered in forests, very little of which remains today because of deforestation. The surviving endemic fauna is still seriously threatened. On Mauritius, the Mascarene teal lived alongside other recently extinct birds such as the dodo, the Mauritian sheldgoose, the red rail, the broad-billed parrot, the Mauritius blue pigeon, the Mauritius scops owl, and the Mauritius night heron. On Réunion, it lived alongside the Réunion sheldgoose, the Réunion ibis, the hoopoe starling, the Mascarene parrot, the Réunion swamphen, the Réunion scops owl, the Réunion night heron, and the Réunion pink pigeon. The Mascarene coot and the Mascarene grey parakeet also lived on both islands. Surviving endemic birds include the echo parakeet, the Mauritius kestrel, and the pink pigeon on Mauritius, and the Réunion harrier, the Réunion bulbul, and the Réunion stonechat on Réunion.