VU
White-necked Petrel Pterodroma cervicalis



Justification

Justification of Red List Category
This species qualifies as Vulnerable because it has a very small range, on two or three very small islands, and it is therefore susceptible to stochastic events and human impacts.

Population justification
The total population has been estimated at c.100,000 mature individuals (1988), roughly equivalent to 150,000 total individuals.

Trend justification
The population is thought to be increasing (Brooke 2004).

Distribution and population

Pterodroma cervicalis breeds on Macauley Island in the Kermadec Islands, New Zealand (c.50,000 pairs in 1988), with a second small colony recently established on Phillip Island, off Norfolk Island (to Australia) with nests increasing from six in 1994 to 20 in 2005 (Priddel et al. 2010). It bred on Raoul Island, also in the Kermadec Islands, early in the 20th century (Taylor 2000). Two birds were found on Raoul Island in 2005 and 2006 covered in seed-burrs, possibly prospecting (Gaskin 2011). It migrates to the tropical and sub-tropical north Pacific Ocean (Spear et al. 1992) with recent sightings in Hawaiian waters (eBird) .
 
The rare sub-species occulta breeds in small numbers on Vanua Lava, Vanuatu (Totterman 2009). In February 2010, it was photographed 60 miles from the site of the original specimens, constituting only the second documented sighting since 1927; a total of 21 individuals were sighted over a three-day period, nine seen rafting before dusk (P. Harrison in litt. 2010).

Ecology

On Macauley Island, White-necked Petrels nest in localised colonies, especially in Sandy Bay, on the slopes above Quadrat Gully, on the gully slopes and floor of Access Gully, on the plateau near Grand Canyon, in Jim’s Gully, and on the upper slopes of Mt Haszard. Although their burrows were once found on forested ridges on Raoul Island, all colonies on Macauley Island are under grass, sedges or fern (G. Taylor pers. comm. in Gaskin 2011). On Raoul, it nested below 300 m on high-altitude ridges (Marchant and Higgins 1990). Two birds were found on the northern terraces of the island (2005 and 2006) covered in the spiny burrs of a native grass (Cenchrus calyculatus) that prevented them from flying. These two birds were presumed prospecting birds and a return to breeding on this rugged island cannot be discounted. This species is also known (from at-sea observations) to be in the waters around Raoul Island in May (Gaskin 2011).  
On Phillip Island, it is a summer breeder. Birds come ashore as early as 11 November, but lay eggs in January (Priddel et al. 2010). Birds nesting on Philip Island differ from the population on Macauley by nesting among boulders and in crevices in rocky habitat with sparse understorey, below a canopy of mature White Oaks Lagunaria patersonia that provide concealment from avian predators (Priddel et al. 2010). It has also been known to nest in artificial cavities. On Phillip Island, the only known nests are at the top of Long Valley, but other areas have potential nest sites (Priddel et al. 2010). It feeds mainly on squid (Heather and Robertson 1997). Little is known of the breeding biology.

Threats

The primary threat faced by this species is invasive mammals. Cats are likely to have been responsible, along with Brown Rat, for the extirpation of the species on Raoul Island. Both are still present on Vanua Lava and pose an existential threat to the species there. Rabbit overgrazing led to considerable erosion on Phillip Island, and their eradication appeared to enable White-necked Petrel to recolonise the island. Domestic Pigs contributed considerably to the degradation of Phillip Island and may have previously impacted the species on Norfolk Island. They are still present on Vanua Lava, and given the impact on other burrowing petrels in the region may be precautionarily assumed to be having a significant impact on this population. Goats dramatically altered the vegetation on Macauley Island prior to their eradication but no clear population impacts were recorded. Polynesian Rats are present in some parts of the range but have not been demonstrated to impact the population. People on Vanua Lava previously harvested chicks from burrows near Mount Suretamatai (Carboneras et al. 2018) however, this affected a minority of the population and is thought unlikely to return.

A native fern, Hypolepis dicksonioides, has formed a monospecies stand across approximately 70% of Macauley Island following the removal of goats in 1970 and presumed successful rat eradication in the first decade of the 21st century (de Lange 2015). This is unsuitable for petrel nesting and may have excluded the species from a considerable area formerly used for breeding (G. Taylor in litt. 2016, de Lange 2015). However, it appears that Homolanthus woodland is invading this monoculture and with time much of this area will become suitable for nesting once again (de Lange 2015), although numbers breeding at present are likely to be considerably lower than were found in 1988 when the population was last estimated (G. Taylor in litt. 2016).

The species is also potentially threatened by climate change because it has a geographically bounded distribution: it is restricted to an island or islands with a maximum altitude of 238 m (BirdLife International unpubl. data).



Conservation actions

Conservation Actions Underway

Goats were removed from Raoul and Macauley in 1984 and 1970, respectively. The eradication of rabbits from Phillip Island in 1985 may have resulted in the species colonising the island in the following years. Polynesian rats were eradicated from Macauley in 2006 and cats and rats were eradicated from Raoul Island between 2002 and 2006 (G. Taylor in litt. 2012). Two birds found on Raoul Island covered in seed burrs in 2005 and 2006 were presumed prospecting birds. Since 2007, automated sound attraction units have been installed on Raoul Island in an attempt to lure the species. However, there has been no evidence so far that this has worked, although breeding on this rugged island cannot be discounted as searches in promising gully areas have not occurred (C. Gaskin in litt. 2016). A study area on Macauley was established in 1988 (G. Taylor in litt. 1999). The Kermadec Islands are nature reserves with access by permit only. Extensive searches were conducted for incubating birds of this species in the upper reaches of Long Valley, the main water catchment of Phillip Island (N. Carlile in litt. 2012).

Conservation Actions Proposed

Map populations on Macauley Island and complete a census. Monitor Macauley every five years to ensure that no establishment of predators has occurred. Monitor the recovery of vegetation on Macauley and any negative effects on the species. Recapture birds in study area to determine data on survival and longevity every five years (Taylor 2000). On Raoul conduct monitoring of acoustic attraction sites where White-necked Petrel calls are broadcast, using playback and spotlights to check for birds flying over land (Northern Terraces) during summer months, and also conduct ground searches of ridges and slopes at western end of island (towards Hutchison Bluff) (C. Gaskin in litt 2016). Survey Vanua Lava and assess threats. 


Identification

43 cm. Large, grey-and-white petrel with distinctive white hindneck. Black cap extends to below eyes. White band extends from throat around hindneck. Grey upperparts, upperwing, with black M across wings. May have grey half-collar across upper breast. White underparts. White underwing with narrow, black trailing edge, black tip, wider black leading edge distal to carpal joint, short, bolder black bar extending towards centre of wing from joint. Similar spp. Distinguished from Juan Fernandez Petrel P. externa by stronger cap contrast, bolder black marking at leading edge of underwing distal to carpal joint. P. externa has grey nape, but some individuals become almost as white-necked as P. cervicalis.

Acknowledgements

Text account compilers
Stuart, A., Taylor, J., Temple, H., Fjagesund, T., Anderson, O., Hermes, C., Calvert, R., Benstead, P., Martin, R., McClellan, R., Moreno, R.

Contributors
Taylor, G.A., MacAllan, I., Tennyson, A., Garnett, S., Carlile, N., Gaskin, C.


Recommended citation
BirdLife International (2022) Species factsheet: Pterodroma cervicalis. Downloaded from http://www.birdlife.org on 02/10/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 02/10/2022.