Justification of Red List Category
This species is listed as Endangered as it has an extremely small population which is restricted to a tiny area of available habitat on one island. Conservation efforts have resulted in the population experiencing continued growth over at the least last decade (D. Portelli in litt. 2016).
The population has recovered to more than the island's carrying capacity (estimated at c.220 individuals [Brook et al. 1997]), was estimated to be stable at around 220–230 birds and 71–74 breeding pairs (NSW National Parks and Wildlife Service 2002) and more recently 240-300 individuals in total, and 232 mature individuals (analysis of Lord Howe Island Board unpubl. data by D. Portelli in litt. 2016).
The population was estimated to be stable (NSW National Parks and Wildlife Service 2002) but ongoing population monitoring has demonstrated a steady increase of approximately 4.5 birds per year since 2004 (Lord Howe Island Board unpubl. data via D. Portelli in litt. 2016).
Hypotaenidia sylvestris is endemic to Lord Howe Island (Australia). In 1788, it was found from sea-level to the tops of the two mountains on the island, but from the mid-19th century, it became restricted to the summits. In the 1970s the population comprised 10 breeding pairs and 3 singletons (Miller & Mullette 1985). In the 1980s, following the eradication of introduced pigs Sus domesticus, birds were reintroduced to two lowland sites (Boat Harbour and Little Slope), and two elevated sites (Goat House and Erskine Valley). Three birds were released within the settlement (Salmon Beach and Kings property) and a fourth was released at the site of capture at Salmon Beach after 66 days in captivity (D. Portelli in litt. 2016). The highest densities are now surrounding the settlement and on Mt Gower, which support over half of the population. In 1997 it was thought that the population had reached the island’s carrying capacity (estimated at c.220 individuals [Brook et al. 1997]), but it is now thought that the population has probably exceeded the estimated carrying capacity, and has only stabilised on Mt Gower. Numbers continue to grow in the Settlement, minor groups continue to decline at Boat harbour-Grey Face and Far Flats, whilst trends at Little Slope is unknown (D. Portelli in litt. 2016). The last population estimate was around 220–230 birds and 71–74 breeding pairs (NSW National Parks and Wildlife Service 2002), though this was from over a decade ago. It is likely that there will be an increase in numbers following successful rodent eradication (H. Bower in litt. 2016).
Hypotaenidia sylvestris is sedentary and highly territorial (Marchant & Higgins 1993). On Mt Gower, it occurs in gnarled mossy forest. At lower altitudes, the species occurs in a wide range of Oceanic Rainforest communities. It also occurs in vegetation associated with residences where supplementary food is available. It forages amongst leaf litter, rotten logs, moss and lichens, feeding on worms, molluscs and invertebrates (Marchant & Higgins 1993). The species is also known to scavenge on residential waste, and prey upon providence petrel chicks and eggs, and rodents (Department of Environment and Climate Change (NSW) 2007). It is monogamous and usually occurs in pairs. Pairs build 3-4 nursery nests on the ground under thick vegetation, in/under root cavities, in petrel burrows and under domestic debris. The breeding season varies between years but females generally lay between August and January and continue raising young until April. However, breeding can occur at any time of year when conditions are suitable In captivity clutch size is 1-4 eggs. Both parents incubate eggs for 20-23 days, and brood and feed chicks. Chicks fledge at 28 days. Females may lay another clutch as soon as 30 days after the initial clutch. Juveniles reach adult size at 12 months, but may start breeding at nine months (Department of Environment and Climate Change (NSW) 2007; Marchant & Higgins 1993). Maximum longevity is fourteen years (Dean Portelli pers comm., Lord Howe Island Board unpublished data, Brook et al. 1997).
The species was eliminated from the lowlands by predation by feral pigs, cats, people and their dogs, as well as disturbance by pigs and goats. These threats were largely eliminated in the 1980s. The only remaining significant threat is the introduced Masked Owl Tyto novaehollandiae which is thought to be responsible for a major decline in the Little Slope population in 1989. Further introductions of exotic predators or the introduction of chronic disease could have serious consequences (Taylor and van Perlo 1998). Buff-banded Rails Hypotaenidia philippensis have re-colonised the island and may conflict with Woodhens, especially during the breeding season (Garnett et al. 2011), though woodhens appear to be the dominant species in this conflict (H. Bower in litt. 2016). Woodhens are likely to be in danger of accidental poisoning during the planned eradication of black rats, which is why it is planned to take as many as possible into captivity while the baits are toxic (Lord Howe Island Board 2009). Natural catastrophes are an additional threat. Population Viability Analysis using VORTEX suggests that the species remains highly susceptible to changes in survival or fecundity (Brook et al. 1997).
Conservation Actions Underway
CITES Appendix I. The species is successfully bred in captivity. Predation and disturbance by dogs is minimised by community support for conservation efforts and any problem dogs are deported (H. Bower in litt. 2016). Goats, cats and pigs have been eradicated (C. Haselden in litt. 2016).
34-42 cm (male), 32-37 cm (female). Large, olive-brown, flightless rail with bright chestnut wings. Olive-brown body, duller on underside. Indistinct, paler supercilium. Bright chestnut wings with narrow, dark brown bars on primaries and primary coverts. Long, decurved, pink bill, more brown towards tip. Red iris. Light pink-brown legs. Juvenile similar, but iris initially dark. Similar spp. Confusion unlikely. Buff-banded Rail G. philippensis is smaller, has bold black-and-white barring on underside, buff breast-band and clear white supercilium. Voice Loud, piercing, repeated whistle, often as duet. Hints Confiding. Spreads wings to sunbathe.
Text account compilers
Allinson, T, Dutson, G., Garnett, S., McClellan, R., North, A., Pilgrim, J., Stattersfield, A., Symes, A. & Taylor, J.
Carlile, N., Bower, H., Haselden, C., Portelli, D. & Frith, C.
BirdLife International (2021) Species factsheet: Hypotaenidia sylvestris. Downloaded from http://www.birdlife.org on 26/10/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 26/10/2021.