Justification 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.

Family/Sub-family Rallidae

Species name author (Meyer, 1883)

Taxonomic source(s) Trewick (1996)

Synonyms Porphyrio mantelli BirdLife International (2000)

Taxonomic note 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.

Identification 63 cm. Very large, bulky, flightless, blue-and-green rail. Deep to peacock-blue head, breast, neck, shoulders. Olive-green and blue back, wings. Huge, red bill and shield. Large, powerful red legs, feet. Juvenile, duller. Dark grey bill and shield. Similar spp. Purple Swamphen P. porphyrio is much smaller and flies. Voice Slow and deep coo-eet, alarm call deep oomf. Hints Leaves behind chewed remains of tussocks, grasses, and very long, fibrous droppings.

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

150 - 220

increasing

670 km²

Yes

Range & population 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)³ and numbered just 250-300 birds⁷. This population has fluctuated between 100-160 birds for the last 20 years⁸ and is thought to be at carrying capacity¹⁶. Translocated populations (1984-1991) exist on four offshore (predator-free) islands - Kapiti, Mana, Tiritiri Matangi and Maud - but have increased only slowly (55 adults in 1998⁶) due to low hatching and fledging rates related to the level of inbreeding of the female of a given pair^3,12. The population on Tiritiri Matangi and other small islands may be close to carrying capacity¹⁴.

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 years⁷.

Threats Introduced red deer Cervus elaphus competing for tussock were a major factor in the post-1940s decline¹⁰, while a series of unusually harsh winters appears important in the recent fluctuations^1,3. Predation by introduced stoat Mustela erminea could be significant^2,3,4 but remains speculative⁵. Other potential competitors or predators are introduced brush-tailed possum Trichosurus vulpecula and the threatened Weka Gallirallus australis⁵. The level of inbreeding in females appears to be related to the low hatching and fledging success exhibited by small island populations¹². Radio-tags have been shown to increase daily energy expenditure, this may influence mortality, particularly in hard winters¹³. On some Tiritiri Matangi at least there is probably some predation by Swamp Harrier Circus approximans¹⁵. The small island populations may be close to carrying capacity¹⁴: on Tiritiri Matangi the 2000/2001 breeding season was largely unsuccessful, primarily due to the increase in territorial disputes amoung proximal family groups¹⁵. Habitat quality on some of the islands is probably in decline as reafforestation reduces the area of foraging habitat¹⁵.

Conservation measures 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 facility¹⁶. 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)³. 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%⁹. A major review of management in 1996-1997 has been completed⁵.

Conservation measures proposed Continue to monitor population trends. Continue all aspects of intensive management. Establish a second mainland population. Promote public awareness by holding captive birds for public display and visits to islands, and through the media⁴. Manage the small islands as a metapopulation, with regular transfers of females between islands and periodic introductions of new breeders from the Fiordland population¹². 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.

References 1. Bunin and Jamieson (1995). 2. Bunin and Jamieson (1996). 3. Bunin et al. (1997). 4. Crouchley (1994). 5. Department of Conservation (1997). 6. Eason and Willans (2001). 7. Heather and Robertson (1997). 8. Maxwell (2001). 9. Maxwell and Jamieson (1997). 10. Mills and Mark (1977). 11. Trewick and Worthy (2001). 12. Jamieson et al (2003). 13. Godfrey et al. (2003). 14. Baber and Craig (2003). 15. Baber and Craig (2003). 16. Greaves (2007).

Text account compilers Phil Benstead (BirdLife International), Simon Mahood (BirdLife International), Rachel McClellan (BirdLife International), John Pilgrim (BirdLife International)

IUCN Red List evaluators Stuart Butchart (BirdLife International), Simon Mahood (BirdLife International)

Recommended citation BirdLife International (2009) Species factsheet: Porphyrio hochstetteri. Downloaded from http://www.birdlife.org on 9/2/2010

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

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