|Scientific Name:||Pterodroma cookii|
|Species Authority:||(Gray, 1843)|
|Red List Category & Criteria:||Vulnerable A2e;D2 ver 3.1|
|Reviewer/s:||Butchart, S. & Symes, A.|
|Contributor/s:||Merton, D., Rayner, M., Taylor, G. & Tennyson, A.|
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.
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).
Native:American Samoa (American Samoa); Chile; Cook Islands; French Polynesia; Mexico; New Zealand; Niue; Norfolk Island; Peru; Pitcairn; United States; United States Minor Outlying Islands; Wallis and Futuna
Present - origin uncertain:Ecuador; French Southern Territories (the); New Caledonia; Samoa; Tokelau; Tonga; Tuvalu
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||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.|
|Habitat and 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).|
|Major Threat(s):||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).
|Citation:||BirdLife International 2012. Pterodroma cookii. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 22 May 2013.|