Okinawa Rail Gallirallus okinawae Scientific name definitions

29–33 cm; one adult 433 g, one fully grown 435 g; wingspan 48–50 cm. Almost flightless; tail very short and decomposed; legs long and strong . Scarcely visible chestnut feathers are present on side of breast ; some white barring on primaries. Most similar to races sulcirostris and limarius of larger, volant H. torquata, but differs in having reduced white facial stripe , and reddish bill and legs. Flightless H. insignis larger, has different head pattern, black undertail-coverts, black bill and pink legs and feet. Sexes alike, but males are larger than females, the total head length and the bill height being the most useful variables for sex discrimination (1 Ozaki, K. (2009). Morphological differences of sex and age in the Okinawa Rail Gallirallus okinawae. Orn. Sci.. 8(2): 117–124. Close ). Immature like adult but has darker bill tip and culmen. Juvenile has paler, olive-tinged upperparts and head, mottled rather than barred underparts, brownish bill, brown iris and fleshy yellow-ochre legs and feet.

N Okinawa, in Ryukyu Is.

Subtropical broadleaf evergreen forest with dense undergrowth and some water; occurs in primary and secondary forest, along forest edges and in small forest patches; also in scrub and around cultivated areas close to forest, where ground is damp or streams, pools or reservoirs occur. Found from sea-level to highest hilltops at 498 m in mountainous areas. Requires standing water for bathing; roosts in trees.

Feeds on wide variety of animals and plants throughout the year, but frequency of occurrence and wet weight of animal matter significantly exceeds those of plant matter; however, the primary dietary component of both sexes, all ages, and throughout the year appears to be land snails (2 Kobayashi, S., Morita, Y., Nakaya, Y., Nagamine, T., Onuma, M., Okano, T., Haga, A., Yamamoto, I., Higa, M., Naruse, T., Nakamura, Y., Denda, T. and Izawa, M. (2018). Dietary habits of the Endangered Okinawa Rail. Orn. Sci.. 17(1): 19–35. Close ). Insects, particularly locusts, and lizards, taken on forest floor; possibly also takes some food  from shallow water when visiting pools to bathe and drink. Recorded eating a dead amphibian on a road.

Highly vocal. Calls  include “kwi kwi kwi ki-kwee ki-kwee”, “ki-ki-ki”, “kyip kyip kyip kyip”, a rolling “kikirr krarr” followed by “kweee” notes on rising scale and becoming almost pig-like squeals, a call rather reminiscent of neighing of horse, and deep bubbling. Normally calls only in early morning, late afternoon and evening, when voice carries further in calm conditions.

ENDANGERED. Confined to largely uninhabited forests of N quarter (Yambaru) of Okinawa I , N from the Shioya to Higashi-son line; S Okinawa is highly developed and well populated. Apparently reasonably common and widespread wherever suitable habitat remains within its very small range. However, population, estimated at c. 1800 birds in 1986, fell dramatically to 810 birds in 2004 and further to 720 in 2005, while range contracted northwards by 40% (3 Ozaki, K., Komeda, S., Baba, T., Toguchi, Y. and Harato, T. (2006). Declining distribution of the Okinawa Rail: impact of introduced predators. Journal of Ornithology. 147(5): 103–104. Close ), with its S distributional boundary gradually moving N into Itaji forest. Surveys in 2006 suggested that population and range had stabilised BirdLife International (2016) Species factsheet: Hypotaenidia okinawae. Downloaded from http://www.birdlife.org on 02/06/2016. . Cause of declines suspected to be introduced Javan mongoose (Herpestes javanicus) (3 Ozaki, K., Komeda, S., Baba, T., Toguchi, Y. and Harato, T. (2006). Declining distribution of the Okinawa Rail: impact of introduced predators. Journal of Ornithology. 147(5): 103–104. Close ) BirdLife International (2016) Species factsheet: Hypotaenidia okinawae. Downloaded from http://www.birdlife.org on 02/06/2016. . Also threatened by continuing deforestation: in recent years pace of development has increased in N, with building of golf courses, dams and public roads  in hitherto continuous pristine forest. Predators probably include domestic cats, dogs, indigenous snakes, weasels (Mustela itatsi) and introduced Large-billed Crows (Corvus macrorhynchos); cats are often observed along forest roads. Roosting in trees probably adaptive to avoid snake predation, but arboreal, nocturnal brown tree snake (Boiga irregularis), which has extirpated tree-roosting H. owstoni from Guam, has been observed on Okinawa and may have potential to establish itself. Roadkill caused 70% of 22 deaths recorded during a five-year study in 1998–2003 (4 Kotaka, N. and Sawashi, Y. (2004). The road-kill of the Okinawa rail Gallirallus okinawae. J. Yamashina Inst. Orn.. 35(2): 134–143. Close ) BirdLife International (2016) Species factsheet: Hypotaenidia okinawae. Downloaded from http://www.birdlife.org on 02/06/2016. . Low genetic diversity suggests a recent population bottleneck but, encouragingly, indicated that conservation action has been implemented in time to save remaining diversity (5 Ozaki, K., Yamamoto, Y. and Yamagishi, S. (2010). Genetic diversity and phylogeny of the endangered Okinawa Rail, Gallirallus okinawae. Genes & Genetic Systems. 85(1): 55–63. Close ). Legally protected in Japan.