NSW National Parks and Wildlife Service, 2002
9. Scientific and Taxonomic Value
The genus Gallirallus has been the subject of much taxonomic review and currently contains sixteen extant and recently extinct species (Taylor, 1996). Various species are found between India, through Indonesia and New Guinea to the islands east of New Zealand. Many species have become flightless, particularly on Pacific Islands, and this has led to many suffering population declines after European settlement. The Lord Howe Woodhen has been in the past placed in the separate genus Tricholimnas with the Critically Endangered New Caledonian Rail (G. lafresnayanus) and the Gilbert Rail (G. conditicius). The latter is known from one specimen from Kiribati and has been considered by some as a juvenile specimen of G. sylvestris that has been mislabeled. The three volant species (Buff-banded G. philippensis, Barred G. torquatus and Slaty-breasted Rails G. striatus) are all widespread and common. However, many of the flightless species are of restricted range and are under threat. These include the Endangered Okinawa (G. okinawae), Near Threatened Roviana (G. rovianae) and the poorly known New Britain (G. insignis) Rails from southern Japan, Solomon Islands and Papua New Guinea respectively. The Guam Rail (G. owstoni) is already extinct in the wild but a captive population remains. Many other island species have not been so lucky with the list of extinct rails including Hawaii's Wake Island (G. wakensis), Dieffenbach's (G. dieffenbachii) and Chatham Islands (G. modestus), both from the islands to the east of New Zealand and Tahiti (G. pacificus) (Fuller, 2002). Sharpe's Rail (G. sharpei) is another species represented by one specimen from an unknown location that is probably extinct. The last remaining species in the genus, the flightless, polytypic Weka (G. australis) is widespread in New Zealand and nearby islands.
The Lord Howe Woodhen is one of the last remaining monotypic, insular species in the genus that has been reasonably well studied. This makes it of significant scientific and taxonomic interest.
The impacts of human activities (including the introduction of exotic species) on the natural terrestrial ecosystems of Lord Howe Island have been significant, notwithstanding the comparatively small area of the island settled by humans (c. 20%). For example, the introduction of Pigs and Goats not only contributed to reducing the Woodhen's range and numbers but also had similar impacts on the Providence Petrel, and possibly other ground-breeding seabirds (eg. Fleshy-footed Shearwaters Puffinis carneipes).
The rehabilitation of the Lord Howe Woodhen is an indication of the extent to which some of the more widespread indirect impacts of human settlement on the island have been controlled. In this respect, the Woodhen is an indicator species for the successful environmental management of the island's terrestrial ecosystems and is an icon for conservation of the island and its wildlife.
The Woodhen is one of a suite of species endemic to Lord Howe Island. One of the principal reasons for the island's listing on the World Heritage Convention is its high species numbers and high level of endemism. For the reasons outlined above, protection of the Woodhen has resulted in the removal of a range of significant threats to this biodiversity.