Porphyrio Brisson, 1760

Hume, Julian Pender, 2019, Systematics, morphology and ecology of rails (Aves: Rallidae) of the Mascarene Islands, with one new species, Zootaxa 4626 (1), pp. 1-107 : 49-51

Genus Porphyrio Brisson, 1760

† Réunion Gallinule (Oiseaux Bleu) ‘ Porphyrio caerulescens ’ ( Sélys-Longchamps, 1848)

Oyseaux bleus Dubois, 1674, p.170; Oustalet, 1897, p.99; Oliver, 1898, p.77; Cheke & Hume, 2008, p.43 Oiseaux bleu La Roque, [1701–10] (in Lougnon, 1992, p.209); Le Gentil, 1727, p.103 Oiseaux bleuff Feuilley, [1705] (in Lougnon 2005, p.128) Gros oiseau Brown, 1773, p.332 Apterornis caerulescens Sélys-Longchamps, 1848, p.294 ; Cyanornis erythrorhynchus Bonaparte, 1854, p.3 ; Hachisuka, 1953, p.155; Hume, 2013, p.219, 2014a, p.37 Porphyrio ( Notornis ?) coerulescens Schlegel, 1857, p.142, 1858 , p.379; 1866a, p.167; Pitot, 1905, p.372 (orthographic error) Porphyrio caerulescens Sharpe, 1894, p.193 ; Olson, 1977, p.365; Hume et al. 2006, p.15; Hume & Walters, 2012, p.113; Cheke, 2013b, p.13; Hume, 2013, p.219, 2017, p.131; Safford & Hawkins, 2013, p.45; del Hoyo & Collar, 2014, pp.352,773 Notornis sp. Oustalet, 1897, p.99 Porphyrio Notornis Pitot, 1914, p.89 Porphyrio madagascariensis Berlioz, 1946, p.8 ; Barré & Barau, 1982, p.34 Porphyrio porphyrio Barré et al. 1996, p.36 Cyanornis coerulescens Hachisuka, 1953, p.155 ; Hume, 2013, p.219; 2014a, p.37 (orthographic error) Porphyrio sp. Strickland (in Strickland & Melville, 1848, p.59); Cheke & Hume, 2008, p.128, pl.8; Safford & Hawkins, 2013,

p.348 Apterornis coerulescens Rothschild, 1907a , p.145, pl.32, 1907b, p.198; Fuller, 1987, p.241; 2001, p.386 (orthographic error) Porphyrio coerulescens Cheke, 1987, p.37 ; Adams et al. 2003, p.344 (orthographic error) Cyanornis (?= Porphyrio ) caerulescens Mourer-Chauviré et al. 2006, p.43

Holotype: None designated.

Measurements: None available.

Type locality: Plaine des Cafres, Réunion, Mascarene Islands.

Distribution: Réunion, Mascarene Islands.

Etymology: Inferred L. caerulescens , bluish, in reference to the all blue plumage colouration.

Remarks: Perhaps the most enigmatic of all rails, the Réunion Gallinule or Oiseaux bleu once occurred on Réunion Island, but as yet not a shred of physical evidence of any kind has been found to resolve its taxonomy. There can be no doubt that it was a large, terrestrial Porphyrio derivative ( Olson 1977; Mourer-Chauviré et al. 1999); the all blue colouration is only found in Porphyrio and not Fulica or Gallinula , and possessed characters—larger size and more robust legs—usually associated with reduced powers of flight. There has been some disagreement regarding the size of the Réunion Gallinule (see Cheke & Hume 2008), as Dubois (1674) stated that they were ‘the size of solitaires’, and Feuilley (1705) that that they were ‘as large as a capon’. However, the Réunion Solitaire Threskiornis solitarius ( Sélys-Longchamps, 1848) would have been no more than 68 cm in total (the size of the African Sacred Ibis Threskiornis aethiopicus ( Latham, 1790) including tail), and capons (or domestic chickens) were approximately the size of the ancestral Red Jungle Fowl Gallus gallus ( Linnaeus, 1758) , up to 70 cm in total length including the long tail, so there is no real size discrepancy between these two contemporary accounts ( Hume 2017).

The Réunion Gallinule was mentioned on a number of occasions by trustworthy observers, being considered good game. Unlike Purple Gallinule, it could easily be caught and killed with sticks, despite being a fast runner, and it was also reluctant to fly ( Cheke & Hume 2008). The Réunion Gallinule appears to have been restricted to the mountains, at least latterly, particularly on a montane plateau called the Plaine des Cafres at around 1,600 –1,800 m in altitude in south-central Réunion (Feuilley 1705; Cheke & Hume 2008) ( Fig. 3 ). The area comprises open woodland in subalpine forest steppe with marshy pools ( Cheke & Hume 2008). Very little was recorded about its ecology. Dubois (1674: 170), while staying on Réunion in 1671–72, gave the first description (my translation):

Oyseaux bleus: As big as the solitaires [Threskiornis solitarius]; their plumage is entirely blue, the beak and the feet red and made like those of hens; they do not fly, but run extremely quickly, so that a dog has difficulty catching them in a chase; they are very good [to eat].

Feuilley (1705) in 1704 described them further (translation from Cheke & Hume 2008: 128):

The Oiseaux bleuff live in the plaines on top of the mountains, and especially on the Plaine des Cafres. They are the size of a large capon, blue in colour. Those that are old are worth nothing to eat because they are so tough, but when they are young they are excellent. Hunting them is not difficult because one kills them with sticks or with stones.

La Roque (in Lougnon 1992: 209) in 1708, while on the Plaine des Cafres, gave the only details about the nesting behaviour (my translation):

One sees there [the Plaine des Cafres] a great numbers of oiseaux bleus which nest amongst grasses and aquatic ferns.

Hébert, in 1708 (1940: 50–51), wrote a report for the East India Company and stated (my translation):

There are also oiseaux bleus, because their plumage is of a dark blue. They do not have another name. They are as large as hens and are good to eat.

Le Gentil (1727) in 1717 and ‘Père Brown’ (1773) around 1730, gave the last unequivocal reports of the oiseaux bleu ( Cheke & Hume 2008). They referred to it as resembling a wood pigeon, which may have been in comparison with the extinct, but undescribed Réunion Blue Pigeon Alectroenas sp., which was also almost all blue ( Hume et al. 2006; Hume 2011a, 2017) (translation from Cheke & Hume 2008: 128):

Towards the east of the island there is a little plateau up a high mountain called the Plaine des Cafres where one finds a large blue bird whose colour is very striking. It resembles a wood-pigeon [in colouration]. It flies but rarely and always barely above the ground, but it walks with surprising speed. The inhabitants have never called it anything other than oiseau bleu; its flesh is quite good and keeps well.

An anonymous account from 1763 (Anon 1763), but possibly written by Brigadier-General Richard Smith ( Hill 1916), may have made the last mention of the Réunion Gallinule, but the writer provides no description of the bird. A number of Mascarene birds were considered tame and without fear of humans; therefore the description cannot be considered unequivocal. The account was further elaborated by Grant (1801), where it appears under ‘Observations on the Isle of Bourbon, in 1763, by an officer in the British Navy’, and includes an insightful contemporary description of the Plaine des Cafres, the prime habitat of the gallinule (from Grant 1801: 167):

The plain des Caffres, is formed by the summits of mountains at a very considerable elevation above the sea: it is said to be twenty miles in extent, and is very flat, and without stones. The access to it is very difficult in certain places, though it may be ascended on horseback. The air is very pure, but as cold as winter’s day in England. When the clouds pass over the surface of the plain, they have all the effect of a gentle rain. A brook runs through the middle of it, which is broad but shallow, has a sandy bottom, and freezes in the winter….On this elevated plain there are small trees, with a broom, furze, a kind of wild oat, and fern, which grows to the height of a shrub. There are also some curious birds, which never descend to the sea-side, and who are so little accustomed to, or alarmed at, the sight of man, that they suffer themselves to be killed by the stroke of a walking stick. It often rains on the sides of the mountains, while this predominating plain is enlivened with the finest weather.

The Réunion Gallinule questionably survived until at least 1763 (Anon 1763; Grant 1801), long after many of the other Réunion birds had become extinct. This was almost certainly due to the remoteness of its habitat (see Feuilley 1705). Its extinction was due primarily to over-hunting, but cats, introduced at the end of the 17th century ( Cheke & Hume 2008), would have quickly eliminated the birds once they had turned feral and reached the remote montane areas. Feral cats occur all over Réunion today, including the remotest, highest peaks, and are still serious predators of native montane birds, especially breeding Barau’s Petrel Pterodroma baraui Jouanin, 1963 ( Faulquier et al. 2009).

Figures

FIGURE 3. Detail of Réunion and original vegetation, showing the place names mentioned in the text (adapted from Cheke & Hume 2008).