Species

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Justification
In 1981, this robin had the smallest population of any bird species for which precise figures were known and it seemed doomed to extinction. Its spectacular recovery, following intensive management, is a renowned conservation success worldwide. Although numbers continue to increase, it still has a very small population and is therefore classified as Endangered.

Taxonomic source(s)
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.
Turbott, E. G. 1990. Checklist of the birds of New Zealand. Ornithological Society of New Zealand, Wellington.

Identification
15 cm. Small, pure black bird. Plumage of sexes alike, but female slightly smaller. Short, slender, black bill. Voice Male song simple phrase of 5-7 notes. Call high-pitched single note.

Distribution and population
Petroica traversi is endemic to the Chatham Islands, New Zealand. It declined rapidly during the late 1800s, and by 1980, the population had fallen to five birds, comprising three males and two females. Intensive management has resulted in a continuous increase in numbers: from seven birds in 1981, to c.116 in 1990, c.170 in 1995 (Butler and Merton 1992, D. V. Merton in litt. 1994), 226 in 1998 and 254 in 1999 (Aikman et al. 2001), including 178 mature birds (S. O'Connor per H. Aikman in litt. 1999). The population is now restricted to Mangere (1 km²) and Rangatira (= South East, 2 km²) islands. The population was feared to be declining, based on census results in 2008, but it seems that the counts gave an underestimate due to weaker methodology and a decline in the species's detectability (E. S. Kennedy in litt. 2011). In 2011-2012, approximately 230 adults were counted in pre-breeding censuses of both island populations (D. Houston per E. S. Kennedy in litt. 2012).


Population justification
Full population surveys in spring 2011 found 190 mature individuals on Rangatira Island, and 34 on Mangere Island. This gives a total population size of 224 mature individuals (per E. S. Kennedy in litt. 2012), with 260 individuals estimated in total (D. Houston in litt. 2011).

Trend justification
The population is increasing owing to intensive conservation efforts (del Hoyo et al. 2007). The most recent population estimate is higher than any since the population crash.

Ecology
It lives in low-altitude scrub forest remnants. It is entirely insectivorous, and feeds on the forest floor and low branches. It usually lays two eggs, and re-lays if a clutch is lost. Young normally begin to breed at two years of age. Birds generally pair for life. Survivorship between 1980 and 1991 indicates a mean life expectancy of four years. "Old Blue", however, the sole breeding female in 1980, lived for over 12 years (Butler and Merton 1992, Heather and Robertson 1997).

Threats
The introduction of rats Rattus spp. and cats, following human settlement, extirpated the birds from all but Little Mangere Island (Butler and Merton 1992). The accidental introduction of mammalian predators to the islands where it currently survives could cause local extinctions. Introduced Common Starlings Sturnus vulgaris, which now number over 1,000 pairs on Rangatira, may provide a serious future threat through introduced disease, competition for nest sites and direct predation (Waugh 2009). Other predators include introduced mice Mus spp. and pigs Sus scrofa, as well as the native Weka Gallirallus australis (E. S. Kennedy in litt. 2012). A potential future threat to this highly inbred species is the arrival of new pathogens. Fire, catastrophic storm events and natural processes of forest recovery, exacerbated perhaps by climate change, are key extrinsic threats to habitat quality and extent. Chronic inbreeding and extensive loss of genetic diversity appear to compromise reproductive output and may yet threaten long-term viability in unforeseen ways. Hybridisation with congeneric Chatham Island Tomtits P. macrocephala chathamensis remains a concern, although the probability of recurrence may be low. The species remains susceptible to outright loss owing to stochastic events (E. S. Kennedy in litt. 2012). 


Conservation actions underway
In 1976, following forest deterioration on Little Mangere Island, the seven surviving birds were relocated to Mangere Island. Prior to reintroduction, thousands of trees were planted to provide sufficient habitat. In 1979, after no breeding and the loss of two birds, a regime of supplementary feeding, and the protection of nests from Common Starlings and seabirds was initiated. In 1980-1981, eggs and chicks were cross-fostered to Chatham Island Warbler Gerygone albofrontata, but this proved unsuccessful. In 1981-1982, "Old Blue's" eggs were cross-fostered to Tomtits P. macrocephala. The three surviving chicks were reintroduced to Mangere Island. This technique was continued, and in 1983, P. traversi was introduced permanently to South East Island. In 1989, intensive management ceased (D. V. Merton in litt. 1994, Heather and Robertson 1997). Annual monitoring of numbers, reproductive success and distribution within habitats continues in both island populations (E. S. Kennedy in litt. 2012). Reforestation on both islands is on-going, and both island habitats are subject to strict quarantine measures to avoid introducing predators, pathogens and other threats. Further research into genetic threats is on-going, and reproductive success is being measured through the closer study of a large population sample on one island (E. S. Kennedy in litt. 2012).

Conservation actions proposed
Continue to monitor population and demographic trends. Restore forest habitat on Mangere Island. Protect populations on Mangere and Rangatira Islands. Establish a third population within the Chatham Islands. Reintroduce birds to Little Mangere Island with landowners' support (H. Aikman in litt. 1999). Continue to work with landowners and Department of Conservation to provide safe habitat on Chatham Island.

Related state of the world's birds case studies

• Back from the brink: four Critically Endangered species saved from extinction

References
King, W. B. 1981. Endangered birds of the world: the ICBP bird Red Data Book. Smithsonian Institution Press and International Council for Bird Preservation [bound reissue of King 1978-1979], Washington, D.C.

Butler, D.; Merton, D. 1992. The Black Robin: saving the world's most endangered bird. Oxford University Press, Auckland.

Heather, B. D.; Robertson, H. A. 1997. The field guide to the birds of New Zealand. Oxford University Press, Oxford, UK.

Department of Conservation. 2002. Black robin recovery plan 2001-2011. Department of Conservation, Wellington, NZ.

Aikman, H.; Davis, A.; Miskelly, C.; O'Connor, S.; Taylor, G. 2001. Chatham Islands threatened birds: recovery and management plans. Department of Conservation, Wellington, New Zealand.

del Hoyo, J.; Elliott, A.; Christie, D. 2007. Handbook of the Birds of the World, vol. 12: Picathartes to Tits and Chickadees. Lynx Edicions, Barcelona, Spain.

Further web sources of information
Alliance for Zero Extinction (AZE) species/site profile. This species has been identified as an AZE trigger due to its IUCN Red List status and limited range.

Click here for more information about the Alliance for Zero Extinction (AZE)

Hear sounds for this species from xeno-canto, the community database of shared bird sounds from around the world.

New Zealand Govt - Dept of Conservation - Recovery Plan

View photos and videos, and hear sounds of this species from the Internet Bird Collection

Text account compilers
Benstead, P., Khwaja, N., Mahood, S., McClellan, R., Taylor, J., Temple, H.

Contributors
Aikman, H., Houston, D., Kennedy, E., Merton, D., O'Connor, S.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2013) Species factsheet: Petroica traversi. Downloaded from http://www.birdlife.org on 18/06/2013. Recommended citation for factsheets for more than one species: BirdLife International (2013) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 18/06/2013.

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.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Additional resources for this species