Broad-billed Parrot - Behaviour and Ecology

Behaviour and Ecology

Little is known about the behaviour of the Broad-billed Parrot. The terms Raven or Crow may have been suggested by the bird's harsh call, its behavioural traits, or just its dark plumage. It may have nested in tree cavities or rocks, like the Cuban Amazon. 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.

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, and 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.

The following description by Jacob Granaet from 1666 identifies its forest habitat and might indicate its demeanour:

Within the forest dwell parrots, turtle and other wild doves, mischievous and unusually large ravens, falcons, bats and other birds whose name I do not know, never having seen before.

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 Julian 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 keel was 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.

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.

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, of which very little remains today, because of 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, Thirioux's Grey Parrot, 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.