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Cook's Petrel Pterodroma cookii

Justification
This species is listed as Vulnerable because, although there have been rapid declines in the past, the improving status of the population and habitat, in particular following the successful eradication of the last introduced predators (Pacific rat) on Little Barrier Island (where by far the largest numbers breed), leading to an increase in fledging success from 5% to 70%. This key step in turning the fortunes of the species followed the earlier eradication of cats from Little Barrier Island in 1980, and Weka from Codfish Island in the early 1980s. Although tiny numbers still occur on Great Barrier Island it may have been effectively extinct as a reproductively viable population for several decades.

Taxonomic source(s)
Brooke, M. de L. 2004. Albatrosses and Petrels Across the World. Oxford University Press, Oxford.
Christidis, L.; Boles, W. E. 2008. Systematics and taxonomy of Australian birds. CSIRO Publishing, Collingwood, Australia.
del Hoyo, J.; Collar, N. J.; Christie, D. A.; Elliott, A.; Fishpool, L. D. C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Barcelona, Spain and Cambridge UK: Lynx Edicions and BirdLife International.
SACC. 2006. A classification of the bird species of South America. Available at: #http://www.museum.lsu.edu/~Remsen/SACCBaseline.html#.
Turbott, E. G. 1990. Checklist of the birds of New Zealand. Ornithological Society of New Zealand, Wellington.

Synonym(s)
Pterodroma cooki Stotz et al. (1996), Pterodroma cooki Collar and Andrew (1988)

Identification
26 cm. Small, grey-and-white petrel. White forehead merging into grey crown. Pale grey crown, neck, back, uppertail-coverts. Darker grey wings showing "M" in flight. Tail slightly darker grey than back. Darker still on tips of central feathers. Outer feathers can be white. White underparts. White underwing with dark tip and dark line along leading edge, extending indistinctly from carpal joint towards body. Similar spp. Separated from most other small gadfly petrels by whiter underwing. Pycroft's Petrel P. pycrofti generally appears darker with darker crown and eye-patch. Outer tail feathers never as white as in some Cook's Petrels. Stejneger's Petrel P. longirostris has darker crown, nape, all dark grey tail. De Filippi's Petrel P. defilippiana has longer, thicker bill, longer tail.

Distribution and population
Pterodroma cookii is endemic to New Zealand, where it breeds on Little Barrier, Great Barrier and Codfish Islands. On Great Barrier, only 12 burrows have been found during the last 25 years; there may be fewer than 20 pairs (Imber et al 2003) and it is extinct as a reproductively viable population, probably owing largely to the presence of rats Rattus spp. (M. Rayner in litt. 2012). On Codfish the population declined from c.20,000 pairs in the early 1900s almost to extinction before predators were removed in 1982; it is now increasing and was estimated at 5,000 breeding pairs in 2007 (Marchant and Higgins 1990, Heather and Robertson 1997, Imber et al 2003, Rayner et al. 2008), and in 2012 was thought to number c.5,000-6,000 breeding pairs (M. Rayner in litt. 2012). The population on Little Barrier is also likely to be increasing (Marchant and Higgins 1990, Taylor 2000), and modelling and spatial analysis has suggested that as many as 286,000 pairs may breed on the island annually (Rayner 2006); six times the number previously suggested (Anon. 2007) Little Barrier/Hauturu Island supports 98% of the world population, with the remainder breeding on Codfish/Whenua Hau Island, off Stewart Island. In 2010, 50 chicks were translocated from Little Barrier to Hawke’s Bay peninsula, south of Cape Kidnappers (Fallwell 2010). The project aims to translocate 350 chicks to build up the colony by 2013, following the fencing of a 2.5-ha site against mice and other predators (Fallwell 2010). Birds migrate to the eastern Pacific Ocean, mainly between 34°S and 30°N (Heather and Robertson 1997). Behavioural, morphological and genetic analyses has produced evidence of a distinct population genetic structure (Rayner et al. 2010), and a recent study of year-round movements indicates two separate migration routes over historic timescales, with birds at Little Barrier migrating to the northern Pacific Ocean and birds at the Codfish Islands migrating to the Humboldt Current (Rayner et al. 2011). These data imply that the two populations may be best treated as different subspecies and represent separate management units (M. Rayner in litt. 2012).




Population justification
M. Rayner (in litt. 2012) estimates over 650,000 mature individuals on Little Barrier in 2007 and c.15,000 mature individuals on the Cod Fish Islands in 2008, thus the total population estimate is rounded to c.670,000 mature individuals.

Trend justification
The population has suffered rapid declines owing to the effects of introduced predators; however, thanks to conservation action and invasive species eradications it is now estimated to be increasing.

Ecology
It breeds in burrows on forested ridges and steep slopes at 300-700 m on Little Barrier and 4-350 m on Codfish; ideal breeding habitat is unmodified forest close to ridgetops with a low and open canopy and many large stems (Marchant and Higgins 1990, Rayner et al 2007). It formerly bred in suitable habitat throughout New Zealand (Imber et al 2003). It feeds mainly on squid, crustaceans and small fish (Heather and Robertson 1997).

Threats
On Little Barrier, introduced cats were a major predator of chicks and adults. Although cats were eradicated, the number of petrel burrows with chicks declined from 32% when both cats and rats were present to just 9% following cat eradication because the population of Rattus exulans (also a predator of petrel chicks) increased dramatically (Heather and Robertson 1997, G. A. Taylor in litt. 1999, Taylor 2000, Rayner et al 2007). On Great Barrier, the population is severely threatened by cats, black rat R. rattus and Pacific rat R. exulans. On Codfish, the population declined owing to severe predation by the introduced Weka Gallirallus australis (Marchant and Higgins 1990).

Conservation Actions Underway
Cats were eradicated from Little Barrier by 1980, and G. australis was eradicated from Codfish between 1980 and 1985 (Taylor 2000). R. exulans was succesfully eradicated from Little Barrier Island in 2004, increasing fledging success from 5% to 70% (Rayner et al 2007, Rayner et al. 2008). An eradication operation took place in August 1998 on Codfish - the outcome of which is unknown (D. V. Merton in litt. 1998). Translocation of chicks from Little Barrier to another potential nest site, Cape Sanctuary in Hawke’s Bay peninsula, is on-going (M. Rayner in litt. 2012). Chicks have been transferred at 50-60 days of age, 20 days before fledging, so that they have time to identify with their new location without needing prolonged feeding (Fallwell 2010). In early 2012, c.250 had been moved during three years (M. Rayner in litt. 2012).
Conservation Actions Proposed
Survey Codfish to locate new breeding burrows and colonies. Monitor breeding success and recruitment on Codfish, and map burrows at five-yearly intervals. Monitor the status of the population on Great Barrier: collect dead birds, tag and map active burrows, record locations of display areas. Implement appropriate pest control if a colony (more than five burrows) is found on Great Barrier. Reintroduce to mainland "islands" (areas of the mainland with intensive predator control) (Imber et al 2003).

References
Anon. 2007. Good news for Cook's Petrel. Forest and Bird: 11.

Fallwell, C. 2010. Home away from home. Forest and Bird 338: 16-18.

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

Imber, M. J.; West, J. A.; Cooper, W. J. 2003. Cook's petrel (Pterodroma cookii): historic distribution,breeding biology and effects of predators. Notornis 50: 221-230.

Marchant, S.; Higgins, P. J. 1990. Handbook of Australian, New Zealand and Antarctic birds, 1: ratites to ducks. Oxford University Press, Melbourne.

Rayner M. J.; Hauber M. E.; Steeves, T. E.; Lawrence, H. A.; Thompson, D. R.; Sagar, P. M.; Bury, S. J.; Landers, T. J.; Phillips, R. A.; Ranjard, L.; Shaffer, S. A. 2011. Contemporary and historic separation of transhemispheric migration between two genetically distinct seabird populations. Nature Communications 2.

Rayner, M. J.; Carragher C. J. F.; Hauber M. E. 2010. Mitochondrial DNA analysis reveals genetic structure in two New Zealand Cook’s petrel (Pterodroma cookii) populations. Conservation Genetics 11: 2073-2077.

Rayner, M. J.; Clout, M. N.; Stamp, R. K.; Imber, M. J.; Brunton, D. H.; Hauber, M. E. 2007. Predictive habitat modelling for the population census of a burrowing seabird: a study of the endangered Cook's Petrel. Biological Conservation 138(1-2): 235-247.

Rayner, M. J.; Hauber, M. E.; Clout, M. N. 2007. Breeding habitat of the Cook's Petrel (Pterodoma cookii) on Little Barrier Island (Hauturu): implications for the conservation of a New Zealand endemic. Emu 107(1): 59-68.

Rayner, M. J.; Parker, K. A.; Imber, M. J. 2008. Population census of Cook's Petrel Pterodroma cookii breeding on Codfish Island (New Zealand) and the global conservation status of the species. Bird Conservation International 18(3): 211-218.

Taylor, G. A. 2000. Action plan for seabird conservation in New Zealand. Department of Conservation, Wellington.

Further web sources of information
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Text account compilers
Anderson, O., Benstead, P., Mahood, S., McClellan, R., Symes, A., Taylor, J., Temple, H.

Contributors
Merton, D., Rayner, M., Taylor, G., Tennyson, A.

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

Recommended citation
BirdLife International (2014) Species factsheet: Pterodroma cookii. Downloaded from http://www.birdlife.org on 22/08/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/08/2014.

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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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

ARKive species - Cook’s petrel (Pterodroma cookii) 0

Key facts
Current IUCN Red List category Vulnerable
Family Procellariidae (Petrels, Shearwaters)
Species name author (Gray, 1843)
Population size 670000 mature individuals
Population trend Increasing
Distribution size (breeding/resident) 85,600,000 km2
Country endemic? Yes
Links to further information
- Additional Information on this species