| Broad-billed Parrot | |
|---|---|
 | |
| Information | |
| Range | Mauritius |
| Estimated Population | 0 |
| Scientific Classification | |
| Kingdom | Animalia |
| Class | Aves |
| Order | Psittaciformes |
| Family | Psittaculidae |
| Conservation Status | |
 Extinct | |
The Broad-billed Parrot or Raven Parrot (Lophopsittacus mauritianus) was a large extinct parrot in the family Psittaculidae. It was endemic to the Mascarene island of Mauritius in the Indian Ocean east of Madagascar. It is unclear what other species it was most closely related to, but it has been classified as a member of the tribe Psittaculini, along with other Mascarene parrots. It had similarities with the Rodrigues parrot, and may have been closely related.
The broad-billed parrot's head was large in proportion to its body, and there was a distinct crest of feathers on the front of the head. The bird had a very large beak, comparable in size to that of the hyacinth macaw, which would have enabled it to crack hard seeds. Subfossil bones indicate that the species exhibited greater sexual dimorphism in overall size and head size than any living parrot. The exact colouration is unknown, but a contemporary description indicates that it had multiple colours, including a blue head, and perhaps a red body and beak. It is believed to have been a weak flier, but not flightless.
The broad-billed parrot was first referred to as the "Indian raven" in Dutch ships' journals from 1598 onwards. Only a few brief contemporary descriptions and three depictions are known. It was first scientifically described from a subfossil mandible in 1866, but this was not linked to the old accounts until the rediscovery of a detailed 1601 sketch that matched old descriptions. The bird became extinct in the 17th century owing to a combination of deforestation, predation by introduced invasive species, and probably hunting as well.
The taxonomic affinities of the broad-billed parrot are undetermined. Considering its large jaws and other osteological features, Edward Newton and Hans Gadow thought it to be closely related to the Rodrigues parrot (Necropsittacus rodricanus), but were unable to determine whether they both belonged in the same genus, since a crest was only known from the latter. Graham S. Cowles instead found their skulls too dissimilar for them to be close relatives.
Many endemic Mascarene birds, including the dodo, are derived from South Asian ancestors, and the English palaeontologist Julian Hume has proposed that this may be the case for all the parrots there as well. Sea levels were lower during the Pleistocene, so it was possible for species to colonise some of the then less isolated islands. Although most extinct parrot species of the Mascarenes are poorly known, subfossil remains show that they shared features such as enlarged heads and jaws, reduced pectoral bones, and robust leg bones. Hume has suggested that they have a common origin in the radiation of the tribe Psittaculini, basing this theory on morphological features and the fact that Psittacula parrots have managed to colonise many isolated islands in the Indian Ocean. The Psittaculini may have invaded the area several times, as many of the species were so specialised that they may have evolved significantly on hotspot islands before the Mascarenes emerged from the sea. A 2011 genetic study instead found that the Mascarene parrot (Mascarinus mascarinus) of nearby Réunion was most closely related to the lesser vasa parrot (Coracopsis nigra) from Madagascar and nearby islands, and therefore unrelated to the Psittacula parrots, undermining the theory of their common origin.
The broad-billed parrot possessed a distinct frontal crest of feathers. Ridges on the skull indicate that this crest was firmly attached, and that the bird, unlike cockatoos, could not raise or lower it. The 1601 Gelderland sketch was examined in 2003 by Hume, who compared the ink finish with the underlying pencil sketch and found that the latter showed several additional details. The pencil sketch depicts the crest as a tuft of rounded feathers attached to the front of the head at the base of the beak, and shows long primary covert feathers, large secondary feathers, and a slightly bifurcated tail. Measurements of sub-fossils known by 1893 show that the mandible was 65–78 millimetres (2.6–3.1 in) in length, 65 mm (2.6 in) in width, the femur was 58–63 mm (2.3–2.5 in) in length, the tibia was 88–99 mm (3.5–3.9 in), and the metatarsus 35 mm (1.4 in). Unlike other Mascarene parrots, the broad-billed parrot had a flattened skull.
Subfossils show that the males were larger, measuring 55–65 centimetres (22–26 in) to the females' 45–55 cm (18–22 in) and that both sexes had disproportionately large heads and beaks. The sexual dimorphism in size between male and female skulls is the largest among parrots. Differences in the bones of the rest of the body and limbs are less pronounced; nevertheless, it had greater sexual dimorphism in overall size than any living parrot. The size differences between the two birds in the 1601 sketch may be due to this feature. A 1602 account by Reyer Cornelisz has traditionally been interpreted as the only contemporary mention of size differences among broad-billed parrots, listing "large and small Indian crows" among the animals of the island. A full transcript of the original text was only published in 2003, and showed that a comma had been incorrectly placed in the English translation; "large and small" instead referred to "field-hens", possibly the red rail and the smaller Sauzier's wood rail.
In spite of the mention of several colours, authors such as Walter Rothschild claimed that the Gelderland journal described the bird as entirely blue-grey, and it was restored this way in Rothschild's 1907 book Extinct Birds. Later examination of the journal by Julian Hume has revealed only a description of the dodo. He suggested that the distinctively drawn facial mask may represent a separate colour. The head was evidently blue, and in 2007, Hume suggested the beak may have been red, and the rest of the plumage greyish or blackish, which also occurs in other members of Psittaculini.
In 2015, a translation of the 1660s report of Johannes Pretorius about his stay on Mauritius was published, wherein he described the bird as "very beautifully coloured". Hume accordingly reinterpreted Hoffman's account, and suggested the bird may have been brightly coloured with a red body, blue head, and red beak; the bird was illustrated as such in the paper by Ria Winters. Possible iridescent or glossy feathers that changed appearance according to angle of light may also have given the impression that it had even more colours. It has also been suggested that in addition to size dimorphism, the sexes may have had different colours, which would explain some of the discrepancies in old descriptions.
Though the broad-billed parrot may have fed on the ground and been a weak flier, its tarsometatarsus was short and stout, implying some arboreal characteristics. The Newton brothers and many authors after them inferred that it was flightless, due to the apparent short wings and large size shown in the 1601 Gelderland sketch. According to Hume, the underlying pencil sketch actually shows that the wings are not particularly short. They appear broad, as they commonly are in forest-adapted species, and the alula appears large, a feature of slow-flying birds. Its sternal keelwas reduced, but not enough to prevent flight, as the adept flying Cyanoramphus parrots also have reduced keels, and even the flightless kakapo, with its vestigial keel, is capable of gliding. Furthermore, Hoffman's account states that it could fly, albeit with difficulty, and the first published illustration shows the bird on top of a tree, an improbable position for a flightless bird. The broad-billed parrot may have been behaviourally near-flightless, like the now-extinct Norfolk Island kaka.
Sexual dimorphism in beak size may have affected behaviour. Such dimorphism is common in other parrots, for example in the palm cockatoo and the New Zealand kaka. In species where it occurs, the sexes prefer food of different sizes, the males use their beaks in rituals, or the sexes have specialised roles in nesting and rearing. Similarly, the large difference between male and female head size may have been reflected in the ecology of each sex, though it is impossible to determine how.
Masauji Hachisuka suggested the broad-billed parrot was nocturnal, like the kakapo and the night parrot, two extant ground-dwelling parrots. Contemporary accounts do not corroborate this, and the orbits are of similar size to those of other large diurnal parrots. The broad-billed parrot was recorded on the dry leeward side of Mauritius, which was the most accessible for people, and it was noted that birds were more abundant near the coast, which may indicate that the fauna of such areas was more diverse. It may have nested in tree cavities or rocks, like the Cuban amazon. The terms raven or crow may have been suggested by the bird's harsh call, its behavioural traits, or just its dark plumage.
Many other endemic species of Mauritius were lost after the arrival of man, so the ecosystem of the island is severely damaged and hard to reconstruct. Before humans arrived, Mauritius was entirely covered in forests, almost all of which have since been lost to deforestation. The surviving endemic fauna is still seriously threatened. The broad-billed parrot lived alongside other recently extinct Mauritian birds such as the dodo, the red rail, the Mascarene grey parakeet, the Mauritius blue pigeon, the Mauritius owl, the Mascarene coot, the Mauritian shelduck, the Mauritian duck, and the Mauritius night heron. Extinct Mauritian reptiles include the saddle-backed Mauritius giant tortoise, the domed Mauritius giant tortoise, the Mauritian giant skink, and the Round Island burrowing boa. The small Mauritian flying fox and the snail Tropidophora carinata lived on Mauritius and Réunion but became extinct in both islands. Some plants, such as Casearia tinifolia and the palm orchid, have also become extinct.
Species that are morphologically similar to the broad-billed parrot, such as the hyacinth macaw and the palm cockatoo, may provide insight into its ecology. Anodorhynchusmacaws, which are habitual ground dwellers, eat very hard palm nuts. Carlos Yamashita has suggested that these macaws once depended on now-extinct South American megafauna to eat fruits and excrete the seeds, and that they later relied on domesticated cattle to do this. Similarly, in Australasia the palm cockatoo feeds on undigested seeds from cassowary droppings. Yamashita suggested that the abundant Cylindraspistortoises and dodos performed the same function on Mauritius, and that the broad-billed parrot, with its macaw-like beak, depended on them to obtain cleaned seeds. Many types of palms and palm-like plants on Mauritius produce hard seeds that the broad-billed parrot may have eaten, including Latania loddigesii, Mimusops maxima, Sideroxylon grandiflorum, Diospyros egrettorium, and Pandanus utilis.
On the basis of radiographs, D. T. Holyoak claimed that the mandible of the broad-billed parrot was weakly constructed and suggested that it would have fed on soft fruits rather than hard seeds. As evidence, he pointed out that the internal trabeculae were widely spaced, that the upper bill was broad whereas the palatines were narrow, and the fact that no preserved upper rostrum had been discovered, which he attributed to its delicateness. G. A. Smith, however, pointed out that the four genera Holyoak used as examples of "strong jawed" parrots based on radiographs, Cyanorhamphus, Melopsittacus, Neophema and Psephotus, actually have weak jaws in life, and that the morphologies cited by Holyoak do not indicate strength. Hume has since pointed out that the mandible morphology of the broad-billed parrot is comparable to that of the largest living parrot, the hyacinth macaw, which cracks open palm nuts with ease. It is therefore probable that the broad-billed parrot fed in the same manner.
Though Mauritius had previously been visited by Arab vessels in the Middle Ages and Portuguese ships between 1507 and 1513, they did not settle on the island. The Dutch Empire acquired the island in 1598, renaming it after Maurice of Nassau, and it was used from then on for the provisioning of trade vessels of the Dutch East India Company. To the Dutch sailors who visited Mauritius from 1598 and onwards, the fauna was mainly interesting from a culinary standpoint. Of the eight or so parrot species endemic to the Mascarenes, only the echo parakeet (Psittacula echo) of Mauritius has survived. The others were likely all made extinct by a combination of excessive hunting and deforestation.
Because of its poor flying ability, large size and possible island tameness, the broad-billed parrot was easy prey for sailors who visited Mauritius, and their nests would have been extremely vulnerable to predation by introduced crab-eating macaques and rats. Various sources indicate the bird was aggressive, which may explain why it held out so long against introduced animals after all. The bird is believed to have become extinct by the 1680s, when the palms it may have sustained itself on were harvested on a large scale. Unlike other parrot species, which were often taken as pets by sailors, there are no records of broad-billed parrots being transported from Mauritius either live or dead, perhaps because of the stigma associated with ravens. The birds would not in any case have survived such a journey if they refused to eat anything but seeds.