|Scientific Name:||Porphyrio hochstetteri|
|Species Authority:||(Meyer, 1883)|
|Taxonomic Notes:||Porphyrio mantelli (Sibley and Monroe 1990, 1993) has been split into P. mantelli (extinct) and P. hochstetteri (extant) following Trewick (1996). Note that in BirdLife International (2000) the name P. mantelli was incorrectly assigned to the extant form, while the name P. hochstetteri was incorrectly assigned to the extinct form.|
|Red List Category & Criteria:||Endangered D ver 3.1|
|Reviewer/s:||Butchart, S. & Symes, A.|
This species is listed as Endangered because it has an extremely small, albeit slowly increasing, population. The recovery programme in place aims to establish a self-sustaining population of over 500 individuals. If the population continues to increase, the species will warrant downlisting to Vulnerable in due course.
|Range Description:||Porphyrio hochstetteri is endemic to New Zealand. Subfossils indicate that it was once widespread in the North and South Islands, but when "rediscovered" in 1948, it was confined to the Murchison Mountains in Fiordland (c.650 km2) (Bunin et al. 1997), and numbered just 250-300 birds (Heather and Robertson 1997). Having declined to its lowest point in the 1970s and 1980s, this population has fluctuated between 100 and 160 birds for the last 20 years (Maxwell 2001) and is thought to be at carrying capacity (Greaves 2007). A captive-rearing programme was initiated in 1985, with the aim of raising populations for translocation to predator-free islands. Translocated populations (1984-1991) now exist on four offshore islands - Kapiti, Mana, Tiritiri Matangi and Maud - but have increased only slowly, with 55 adults in 1998 (Eason and Willans 2001), due to low hatching and fledging rates related to the level of inbreeding of the female of a given pair (Bunin et al. 1997, Jamieson et al 2003). The population on Tiritiri Matangi and other small islands may be close to carrying capacity (Baber and Craig 2003).|
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The total population is currently estimated to number 227 adult birds, roughly equivalent to 340-350 individuals in total.|
|Habitat and Ecology:||It originally occurred throughout forest and grass ecosystems. Today it is restricted to alpine tussock grasslands on the mainland and feeds primarily on juices from the bases of snow tussock and a species of fern rhizome. It eats introduced grasses on the islands. It usually lays two eggs. Chicks can begin breeding at the end of their first year, but usually start in their second. It is long-lived, probably 14-20 years (Heather and Robertson 1997).|
Introduced red deer Cervus elaphus competing for tussock were a major factor in the post-1940s decline (Mills and Mark 1977), while a series of unusually harsh winters appears important in the recent fluctuations (Bunin and Jamieson 1995, Bunin et al. 1997). Recent research has confirmed predation by introduced stoats Mustela erminea to also be a key threat (Crouchley 1994, Bunin and Jamieson 1996, Bunin et al. 1997, Wickes et al. 2009). Other potential competitors or predators include the introduced brush-tailed possum Trichosurus vulpecula and the threatened Weka Gallirallus australis (Department of Conservation 1997). The level of inbreeding in females appears to be related to the low hatching and fledging success exhibited by small island populations (Jamieson et al. 2003). Radio-tags have been shown to increase daily energy expenditure, which may influence mortality, particularly in hard winters (Godfrey et al. 2003). On some Tiritiri Matangi at least there is probably some predation by Swamp Harrier Circus approximans (Baber and Craig 2003). The small island populations may be close to carrying capacity (Baber and Craig 2003): on Tiritiri Matangi the 2000-2001 breeding season was largely unsuccessful, primarily due to the increase in territorial disputes among proximal family groups (Baber and Craig 2003). The small island populations have also been shown to be threatened by inbreeding depression (Grueber et al. 2010). Habitat quality on some of the islands is probably in decline as reforestation reduces the area of foraging habitat (Baber and Craig 2003). Hunting by humans is likely to have contributed historically to its decline (Wickes et al. 2009).
Conservation Actions Underway
Since the 1960s, deer have been controlled in the Murchison Mountains. A new mainland population in the Stuart Mountains is being established with surplus birds from the Burwood Bush Captive Rearing facility (Greaves 2007). Stoat trapping is also undertaken in the mountains (Wickes et al. 2009). Island populations of the species are managed intensively, optimising breeding success by supplementary feeding, inter-island transfers (also minimising inbreeding), and egg manipulation (primarily removal of infertile eggs to promote re-nesting) (Bunin et al. 1997). Captive-breeding efforts have increased the rate of survival to one year of age (when birds are released into the wild) by 50-60% to 90% (Maxwell and Jamieson 1997). A major review of management in 1996-1997 has been completed (Department of Conservation 1997). Conservation Actions Proposed
Continue to monitor population and productivity trends, as well as carrying out research on captive populations. Establish a second mainland population, perhaps by fencing around the captive breeding centre at Burwood, and/or introducing the species to another area of Fiordland (Wickes et al. 2009). Promote public awareness by holding captive birds for public display and visits to islands, and through the media (Crouchley 1994). Manage the small islands as a metapopulation, with regular transfers of females between islands and periodic introductions of new breeders from the Fiordland population (Jamieson et al. 2003). Remove individuals with high mean kinship values from island population, and replace them with individuals from the Fiordland population to avert inbreeding depression (Grueber et al. 2010). Consider the introduction of birds to another island which could support a larger population. On small islands, plant clumps of native shrubs such as Coprosma spp. at 20-30 metre intervals in open grassy areas to provide cover from C. approximans. Research the viability of reintroducing bush snow-grass Chionochloa conspicua throughout the Murchison Mountains.
|Citation:||BirdLife International 2012. Porphyrio hochstetteri. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 20 May 2013.|
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