Echo Parakeet

The echo parakeet (Psittacula eques) is a species of parrot endemic to the Mascarene Islands of Mauritius and formerly Réunion. It is the only living native parrot of the Mascarene Islands; all others have become extinct due to human activity. Two subspecies have been recognised, the extinct Réunion parakeet (for a long time known only from descriptions and illustrations) and the living echo parakeet, sometimes known as the Mauritius parakeet. The relationship between the two populations has been historically disputed. A 2015 DNA study compared the DNA of echo parakeets with a skin sample thought to be from a Réunion parakeet and determined them to be subspecies of the same species. However, it has also been suggested they did not constitute different subspecies. As it was named first, the binomial name of the Réunion parakeet is used for the species; the Réunion subspecies thereby became P. eques eques, while the Mauritius subspecies became P. eques echo. Their closest relative was the extinct Newton's parakeet of Rodrigues, and the three are grouped among the subspecies of the rose-ringed parakeet (from which they diverged) of Asia and Africa.

The echo parakeet is 34–42 cm (13–17 in) long, weighs 167–193 g (5.9–6.8 oz), and its wingspan is 49–54 cm (19–21 in). It is generally green (the female is darker overall) and has two collars on the neck; the male has one black and one pink collar, and the female has one green and one indistinct black collar. The upper bill of the male is red and the lower blackish brown; the female's upper bill is black. The skin around the eyes is orange and the feet are grey. Juveniles have a red-orange bill, which turns black after they fledge, and immature birds are similar to the female. The Réunion parakeet had a complete pink collar around the neck, whereas it tapers out at the back in the Mauritius subspecies. The related rose-ringed parakeet which has been introduced to Mauritius is similar, though slightly different in colouration and smaller. The echo parakeet has a wide range of vocalisations, the most common sounding like "chaa-chaa, chaa-chaa".

As the species is limited to forests with native vegetation, it is largely restricted to the Black River Gorges National Park in the southwest of Mauritius. It is arboreal and keeps to the canopy, where it feeds and rests. It nests in natural cavities in old trees, and clutches usually consist of two to four white eggs. The female incubates the eggs, while the male feeds her, and the young are brooded by the female. Not all pairs are strictly monogamous, as breeding between females and "auxiliary males" is known to occur. The echo parakeet mainly feeds on the fruits and leaves of native plants, though it has been observed to feed on introduced plants. The Réunion parakeet probably went extinct due to hunting and deforestation, and was last reported in 1732. The echo parakeet was also hunted by early visitors to Mauritius and due to destruction and alteration of its native habitat, its numbers declined throughout the 20th century, reaching as few as eight to 12 in the 1980s, when it was referred to as "the world's rarest parrot". An intensive effort of captive breeding beginning in the 1990s saved the bird from extinction; the species was downgraded from critically endangered to endangered in 2007, and the population had reached 750 birds by 2019, whereafter it was classified as vulnerable.

Taxonomy

Green parakeets were mentioned in the accounts of early travelers to the Mascarene Islands of Réunion and Mauritius. They were first recorded on Réunion in 1674 by the French traveler Sieur Dubois, and on Mauritius in 1732 by the French engineer Jean-François Charpentier de Cossigny. The green parakeets of Réunion were referred to as perruche à double collier ("double-collared parakeet") by the French naturalists Mathurin Jacques Brisson, in 1760, Comte de Buffon, in 1770–1783, and François Levaillant, in 1801–1805, who described them from specimens that reached France. In 1783, the Dutch naturalist Pieter Boddaert coined the scientific name Psittacus eques, based on a plate by the French artist François-Nicolas Martinet, which accompanied Buffon's account of the Réunion bird in his work Histoire Naturelle. The specific name eques is Latin for "horseman", and refers to the military colours of a French cavalryman. Martinet's plate was drawn after a specimen that was part of the collection in the Cabinet Aubry in Paris, and the plate is the type illustration. Whether the contemporary illustrations were based on live or stuffed specimens is unknown; though as all show different poses, this suggests several specimens existed if they were mounted. Neither is it clear if the descriptions from France were based on different or the same imported specimens nor how many reached Europe. Levaillant knew of two specimens, and as many as five may have existed.

The green parakeets of Mauritius and Réunion were usually treated together in historical literature, and their histories have consequently been muddled. In 1822, the British ornithologist John Latham listed the parakeet of Réunion (and "other parts of the same latitude") as a variety of the rose-ringed parakeet, which he referred to as Psittica torquata, based on a name coined by Brisson. In 1876, the British ornithologists and brothers Alfred and Edward Newton pointed out that the avifauna of Réunion and Mauritius were generally distinct from each other, and that this might, therefore, also be true of the parakeets. They suggested the new name Palaeornis echo for the Mauritian species (referring to Echo, a nymph in Greek mythology), while noting that it was very similar to the by-then extinct Réunion species (which retained the name Palaeornis eques). The Italian ornithologist Tommaso Salvadori united the two again in 1891, while giving only Mauritius as the habitat. In 1907, British zoologist Walter Rothschild supported the separation of the two species on account of the other birds of Réunion and Mauritius being distinct, while noting that how they differed was unknown. The American ornithologist James L. Peters listed the parakeet of Mauritius as a subspecies of the rose-ringed parakeet (Psittacula krameri) in 1937; P. k. echo. He thereby replaced the genus name Palaeornis with Psittacula, wherein he also classified other extant parakeets of Asia and Africa. In 1967, the American ornithologist James Greenway considered the parakeets of both Mauritius and Réunion to be subspecies of the rose-ringed parakeet, and found it probable that they differed from each other, unless the birds on Réunion had simply been introduced, though how was unknown.

In a 1987 book about Mascarene birds, the British ecologist Anthony S. Cheke stated that the parakeets of Mauritius and Réunion apparently belonged to the same species. In the same publication (a chapter which was one of the few studies of echo parakeet biology), British conservation biologist Carl G. Jones noted that the parakeets of the western Indian Ocean were probably derived from Indian Alexandrine parakeets (P. eupatria), losing the characteristics of that bird the farther they dispersed. Jones also reported an old parakeet skin, possibly from Réunion, in the Royal Museum of Scotland, Edinburgh (a study skin catalogued as specimen NMS.Z 1929.186.2). Originally part of the collection of the French taxidermist Louis Dufresne, it was bought by the University Museum of Edinburgh (which later became the Royal Museum) in 1819, along with the rest of his natural-history collection. The specimen's original label referred specifically to Levaillant's plate of the "perruche a double collier", illustrated by the French artist Jacques Barraband, which was meant to depict the parakeet of Réunion. Jones cautioned that the collection data of such early specimens may not always be reliable, and that the skin could possibly have come from Mauritius, instead. Whether the Edinburgh skin was the basis of Martinet's type illustration is unknown. Jones did not find the skin particularly different from those of living echo parakeets (or the old French descriptions), based on examination of photographs. He agreed with previous authors that the parakeets of Mauritius and Réunion belonged to the same species (P. eques, the oldest name), but that they should be kept separate at the subspecific level (as P. eques eques and P. eques echo), due to lack of further information about the extinct bird.

The living parakeet of Mauritius has been referred to by the English common name "echo parakeet" since the 1970s, based on the scientific name, and has also been called the Mauritius parakeet. The local Mauritian name is cateau vert, kato, or katover (derived from French). The Réunion population has been referred to as the Réunion parakeet and the Réunion ring-necked parakeet, but has also been subsumed under the common name of the echo parakeet.

Evolution

In 2004, British geneticist Jim J. Groombridge and colleagues examined the DNA of Psittacula parakeets to determine their evolutionary relationships, and found that the echo parakeet had diverged from the Indian subspecies of rose-ringed parakeet (P. k. borealis) rather than the African subspecies (P. k. krameri). They found that the echo parakeet diverged relatively recently compared to other Psittacula species, between 0.7 and 2.0 million years ago, which appears to coincide with volcanic inactivity on Mauritius between 0.6 and 2.1 million years ago. The ancestors of the echo parakeet may, therefore, have migrated southwards from India across the Indian Ocean, and arrived at the time the island was formed. The authors cautioned that their interpretations were limited by the absence of DNA from the extinct Seychelles parakeet (P. wardi) and Newton's parakeet (P. exsul) from other Indian Ocean islands.

In 2007, based on morphological evidence, British palaeontologist Julian P. Hume found the echo parakeet to be more closely related to the Alexandrine parakeet than to the rose-ringed parakeet. He noted that the skeletal anatomy of the echo parakeet was mainly known from fossil bones, as it was the Mauritian parrot most commonly found in cave deposits, and that skeletons are rare in museum collections. Hume pointed out that many birds endemic to the Mascarene Islands are derived from South Asian ancestors, and that a South Asian provenance was probable for the parrots, as well. Sea levels were lower during the Pleistocene, so species island hopping to the isolated islands was possible. In spite of most Mascarene parrots being poorly known, fossil remains show that they shared features such as enlarged heads and jaws, reduced pectoral elements, and robust leg elements. Hume suggested they shared a common origin within the Psittaculini radiation, based on morphological features and the fact that Psittacula parrots have managed to colonise many isolated islands in the Indian Ocean. In 2008, Cheke and Hume suggested that this group may have invaded the area several times, as many of the species were so specialised that they may have diverged on hot spot islands before the Mascarenes emerged from the sea.

A 2011 DNA study by British biologist Samit Kundu and colleagues found the echo parakeet samples grouped between two subspecies of the rose-ringed parakeet, P. k. krameri and P. k. borealis. They suggested that since some of the Indian Ocean island species had diverged early within their clades, including the echo parakeet within P. krameri, Africa and Asia may have been colonised from there rather than the other way around. They found the echo parakeet to have diverged between 3.7 and 6.8 million years ago, which, if correct, could imply that speciation had occurred before the formation of Mauritius. These researchers were unable to extract DNA from the Edinburgh specimen.

In 2015, British geneticist Hazel Jackson and colleagues managed to obtain DNA from a toe pad of the Edinburgh specimen and compare it with specimens from Mauritius. They found that within the P. krameri clade, Newton's parakeet from Rodrigues was ancestral to the Mauritius and Réunion parakeets, diverging from them 3.82 million years ago and that the latter two had diverged just 0.61 million years ago, differing by 0.2% from each other. The researchers concluded that the low level of divergence between the Mauritius and Réunion populations was consistent with them being distinct at the subspecific level. The following cladogram shows the phylogenetic position of the Mauritius and Réunion subspecies, according to Jackson and colleagues, 2015:

In 2018, the American ornithologist Kaiya L. Provost and colleagues found the Mascarene parrot (Mascarinus mascarinus) and Tanygnathus species to group within Psittacula, making that genus paraphyletic (an unnatural grouping), and stated this argued for breaking up the latter genus. To solve the issue, the German ornithologist Michael P. Braun and colleagues proposed in 2019 that Psittacula should be split into multiple genera. They placed the echo parakeet in the new genus Alexandrinus, along with its closest relatives, Newton's parakeet and the rose-ringed parakeet.