Rails and coots (Rallidae)
Rails have managed to reach almost every oceanic archipelago throughout the world and can, within a few generations, evolve flightlessness, ideal adaptations for oceanic island speciation and endemism. The Mauritius red rail Aphanapteryx bonasia and Leguat’s rail Aphanapteryx (Erythromachus) leguati from Rodrigues are two examples of extreme divergence; their phylogenies are now difficult to determine. The genus Aphanapteryx is characterised by hair-like plumage, long de-curved bills, vestigial wings and strong, robust legs. They appear to have been opportunist omnivores and, particularly in the case of A. bonasia of Mauritius, were able to survive for a long time alongside man and rats. The introduction of cats in the late 17th century, however, proved disastrous and the rails were not seen again after 1693.
The Rodrigues species A. leguati is distinct from A. bonasia in a number of characteristics, so there is good reasoning for retaining Erythromachus for this species. They were reported common, fat and unable to run after gorging themselves on tortoise eggs in 1691-3. Tafforet also mentioned them, however, Pingré in 1761 stated that they were now extinct. Again, cats seem to have been the culprits but severe deforestation may also have been a serious factor.
Rails of the genus Aphanapteryx appear never to have reached Réunion. The Réunion solitaire, Threskiornis solitaria probably occupied the same ecological niche.
The white-throated rail Dryolimnas cuvieri is widely distributed in Madagascar, where the volant nominate form is reasonably common. There are two closely related subspecies, the flightless Aldabran rail D. c. aldabranus from Aldabra, which holds the distinction of being the last surviving Indian Ocean flightless rail, and the recently extinct Assumption Island rail D. c. abbotti, which was also in the process of becoming flightless. A second species of Dryolimnas, only tentatively placed in this genus, has recently been described from fossil remains collected on Réunion. The Réunion rail D. augusti was morphologically similar, although larger, to the Aldabran species and was probably also flightless. Ironically, the type specimen of Madagascar white-throated rail Dryolimnas c. cuvieri was collected on Mauritius in 1809 and is identical to Madagascar specimens.
It is possible that an endemic D. cuvieri or a Dryolimnas species once inhabited Mauritius. In 1638, Peter Mundy mentions ‘hens of a wheaten colour,’ which may refer to this species. Furthermore, Cowles in 1987 identified D. cuvieri from bones obtained from the Mare aux Songes, previously ascribed to the purple gallinule Gallinula chloropus by Newton & Gadow in 1893.
The most enigmatic of all rails once occuring on the Mascarenes is the ‘Oiseaux bleu,’ a mysterious bird that lived on the Plaine des Cafres, Réunion. They were considered good game and although able to fly, could easily be caught and killed with sticks. As their colour was described as blue with red beak and legs, the oiseaux bleu is generally considered to represent a large Porphyrio gallinule. Despite being described as Porphyrio (Cyanornis) coerulescens, no skeletal evidence of any kind has been found to resolve the taxonomy. Whatever its generic placement turns out to be, the blue bird was last reported around the middle of the 18th century.
Coots and moorhens are adaptable aquatic rails. The common moorhen Gallinula chloropus is found on most western Indian Ocean islands and appears to be a recent colonist to Mauritius, whilst the only surviving coot in the region is the red-knobbed coot Fulica cristata of Madagascar. A coot of the genus Fulica was once found on Mauritius and Réunion. From fossil skeletal material collected in the Mare aux Songes, Milne-Edwards in 1867 described the Mauritian species as Fulica newtoni, a large, flightless derivative of F. atra or a derivative of F. cristata. Recently collected fossil material from Réunion suggests that F. newtoni is undifferentiated on Réunion and Mauritius.