Hypotaenidia okinawae 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Gruiformes Rallidae

Scientific Name: Hypotaenidia okinawae (Yamashina & Mano, 1981)
Common Name(s):
English Okinawa Rail
Gallirallus okinawae (Yamashina & Mano, 1981)
Rallus okinawae Yamashina & Mano, 1981 — Collar and Andrew (1988)
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
Taxonomic Notes: Hypotaenidia okinawae (del Hoyo and Collar 2014) was previously placed in the genus Gallirallus.
Identification information: 30cm. Medium-sized, nearly flightless, short-tailed rail with long, strong legs. Dark olive-brown upperparts. Black sides of head and underparts, barred with white from lower neck to undertail-coverts. White loral spot and line from rear base of eye down side of neck. Red bill and legs. Juvenile has paler upperparts with mottled white underparts. Voice Highly vocal. Calls include a loud kyo, a kwi kwi kwi ki-kwee ki-kwee, often answered by a ki-ki-ki and a kyip kyip kyip given by a pair. Other calls include a rising pig-like squeal and a deep bubbling gu-gu-gugugugu and gyu-gyu-gyagyagya.

Assessment Information [top]

Red List Category & Criteria: Endangered B1ab(i,ii,iii,v);C2a(ii) ver 3.1
Year Published: 2016
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Ozaki, K. & Takashi, H.
Facilitator/Compiler(s): Benstead, P., Bird, J., Pilgrim, J. & Taylor, J.
This species is listed as Endangered because it has a single, very small population within a very small range on just one island, and both its range and population are undergoing continuing declines as a result of introduced predators and the loss of forest to logging, infrastructure development, agriculture and construction of golf courses.

Previously published Red List assessments:

Geographic Range [top]

Range Description:Hypotaenidia okinawae is endemic to Okinawa Island, Japan, where it is confined to Kunigami-gun (=Yambaru) in the northern quarter of the island, north of Shioya and Higashi-son. Surveys from 1996 to 2004 found that numbers declined dramatically from c.1,800 individuals in 1986 to an estimated 717 individuals, with its range contracting northwards by 40% since 1985-1986 (Ozaki et al. 2006). Surveys in 2006 did not detect any further contraction in range size, suggesting that measures to control introduced Javan Mongoose Herpestes javanicus have had some success (K. Ozaki in litt. 2006). Low genetic diversity in the species's population is suggestive of a recent population bottleneck, with genetic diversity likely to be negatively affected by habitat fragmentation (Ozaki et al. 2010). 

Countries occurrence:
Additional data:
Continuing decline in area of occupancy (AOO):Yes
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:990
Continuing decline in extent of occurrence (EOO):YesExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:1Continuing decline in number of locations:Unknown
Extreme fluctuations in the number of locations:No
Upper elevation limit (metres):500
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Surveys conducted between 1996 and 2004 estimated 717 individuals at the end of the period. Repeat surveys in 2006 found no further decrease (Ozaki in litt. 2006). On this basis the population is estimated at c.720 individuals, equivalent to c.480 mature individuals. Brazil (2009) estimates the population of Japan to number c.100-10,000 breeding pairs.

Trend Justification:  Hanawa and Morishita (1986) estimated the population to be c.900 pairs or 1,500-2,100 birds. Ozaki et al. (2006) reported a reduction to 717 individuals by 2004 (with no further decline by 2006). Hence, a decline of 37% occurred over ten years and the negative population trend is therefore best placed in the band 30-49%, and considered on-going.
Current Population Trend:Decreasing
Additional data:
Number of mature individuals:480Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:No
No. of subpopulations:1Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:Yes
No. of individuals in largest subpopulation:100

Habitat and Ecology [top]

Habitat and Ecology:It occurs in a variety of habitats, including primary and secondary, evergreen and broadleaf subtropical forest, often with a dense undergrowth of ferns, near to streams, pools or reservoirs and cultivated areas close to forest. It is almost, but not completely, flightless and feeds on the forest floor, and occasionally in shallow water, where it takes invertebrates and lizards. Nests are made on the ground during the breeding season, from May-July. The usual clutch-size is two to three eggs.

Systems:Terrestrial; Freshwater
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):3.4
Movement patterns:Not a Migrant

Threats [top]

Major Threat(s): Logging, dam construction and associated road-building, agricultural development and golf course construction are causing forest loss and fragmentation. Recent research (Ozaki et al. 2006) indicates that its range on the island has contracted to the north (resulting in a 25% decrease in extent of occurrence). The research strongly implies that introduced Javan mongoose Herpestes javanicus are the cause of this contraction, although feral dogs, cats and introduced Jungle Crows Corvus macrorhynchos are also possible predators (K. Ozaki in litt. 2006). Road kill was the cause of mortality in 70% of the 22 recorded deaths during a five year study from 1998 to 2003 (Kotaka and Sawashi 2004) and at least 19 deaths in 2011 (Shimpo 2011).  Mortality was worst during the breeding season, suggesting that road kill lowers recruitment to the adult population and may be causing localised declines.

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
It is legally protected in Japan. Yonaha-dake and parts of Mt Ibu and Mt Nishime are designated as protected areas. Conservation organisations have been promoting the protection of Okinawa's forests since 1970 and have bought some sites on Mt Yonaha to establish private wildlife reserves. In 1996, Yambaru was designated as a national park. The species was the focus of several surveys conducted between 1996 and 2006. Some areas of fencing and a trapping regime have been employed to reduce predation on the species by introduced mammals (Ozaki et al. 2006). Traffic calming measures have been taken in some areas to reduce the number of road kills. Japan's Ministry of Environment plans to undertake a captive breeding programme for the species, aiming to obtain a captive population of 200 individuals. Genetic analysis of 20-25% of the population has indicated that minor haplotypes persist, suggesting that conservation measures have been implemented in time to preserve most of the species's genetic diversity (Ozaki et al. 2010).

Conservation Actions Proposed
Establish monitoring and research programmes and support captive breeding programmes. Provide full protection for the whole area of Yambaru. Continue to expand research and actions to control introduced predators. Instigate a conservation education programme for Okinawa using this species and Okinawa Woodpecker Sapheopipo noguchii as flagship species. Develop measures to further reduce road kills. Continue fencing areas to reduce predation. In 2016 plans were announced by the Japan's Environment Ministry to designate a new national park in the northern part of the island to help this species (JiJi Press 2016).

Citation: BirdLife International. 2016. Hypotaenidia okinawae. The IUCN Red List of Threatened Species 2016: e.T22692412A93352408. . Downloaded on 19 July 2018.
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