White-throated Rail Dryolimnas cuvieri (Pucheran, 1845)

Rallus cuvieri: Pucheran, 1845, p.279 (Mauritius)

Rallus gularis: Hartlaub, 1877, p.337; Milne-Edwards & Grandidier, 1879, p.569, pls.230b, 232; Guérin, 1942, 2(6) (auctorum nec Horsfield, 1822, p.196)

Dryolimnas cuvieri: Sharpe, 1894, p.70

Dryolimnas cuvieri cuvieri: Sclater, 1924, p.101; Rountree et al. 1952; Dickinson & Remsen, 2013, p.155; del Hoyo & Collar, 2014, pp.344

Holotype: MNHN-ZO-2011- 535 ♀ (Fig. 31). The holotype was described from a live specimen captured on Mauritius in 1809 by Colonel M. Mathieu (Schlegel & Pollen 1868), who was attached to the naval artillery and supplied an important collection of animals to the MNHN (Cheke & Hume 2008; Hume 2011a).

Measurements: See Appendix 2.

Type locality: Mauritius, Mascarene Islands (vagrant).

Distribution: Madagascar, Mayotte, (Comoros), Mauritius, Aldabra Atoll (ssp aldabranus) and Assumption Island (ssp abbotti).

Etymology: After Léopold Chrêtien Frédéric Dagobert Baron Cuvier (1769–1832), French anatomist, and better known by his assumed name, Georges Cuvier (Jobling 2009).

Diagnosis: In skeleton, as for genus.

Description of skin (Fig. 31): In nominate, head, neck and breast vinous-chestnut; chin and throat white; mantle and scapulars to upper-tail coverts greenish-olive, with blackish-brown streaks on lower mantle, scapulars and back; tail olive-brown; flanks, belly and thighs greenish olive-brown; hind flanks and belly buffy-white barred black; median undertail-coverts dark brown barred white and lateral undertail-coverts white; wings olive-brown tinged greenish, with darker central streak on tertials; rostrum blackish, mandible red with blackish tip; iris reddishorange to reddish-brown; legs and feet greenish-grey or brownish-grey. Sexes alike. In D. c. aldabranus, smaller, with much reduced wing than nominate (Table 2); top and sides of head more olive-brown; upperparts slightly paler, streaking reduced or absent; wings dull grey-brown; lower flanks and belly paler with less distinct white barring; bill blackish-brown, with pink on lower half of rostrum and basal third of mandible; iris orange-brown; legs and feet dark brown or black. Sexes alike. In D. c. abbotti, smaller than nominate, with wing intermediate in length between nominate and D. c. aldabranus (Table 3); upperparts paler, more greenish-olive; dark streaks variable, narrower, fainter or absent; white on throat more extensive, reaching upper breast; broader white barring on underside; bill black, basal third of mandible bright red; legs and feet dark brown.

Remarks: The White-throated Rail is divided into three subspecies, nominate and volant D. c. cuvieri, which is found widely on Madagascar and as a vagrant on both Mayotte, Comoros, and Mauritius (Safford & Hawkins 2013), while flightless and poorly volant forms, D. c. aldabranus and D. c. abbotti are endemic to Aldabra Atoll and Assumption Island respectively (Fig. 1); D. c. abbotti is now extinct (Safford & Hawkins 2013; Hume 2017). The holotype of the nominate collected on Mauritius is undifferentiated in colouration and wing and tarsus measurements from those on Madagascar, which is the normal distribution of this species (Ripley 1977; Taylor & van Perlo 1998). Dryolimnas cuvieri was considered to be either a former resident on Mauritius, or a vagrant, despite the holotype having enlarged ovaries (Rountree et al. 1952; Cheke 1987; Cowles 1987), but no specimens have been recorded on Mauritius since the type was collected. The discovery of subfossil remains have confirmed that an endemic, poorly volant or flightless species once occurred on the island (see below).