VU
White-chinned Petrel Procellaria aequinoctialis



Justification

Justification of Red List Category
This species is classified as Vulnerable because of suspected rapid declines, although almost no reliable estimates of historical populations exist. Very high rates of incidental mortality in longline fisheries have been recorded in recent decades; the probability that these circumstances will continue, the susceptibility of chicks to predation, and the degradation of breeding habitat indicate that a rapid and on-going population decline is likely. An updated assessment of the population on South Georgia is needed in order to fully assess the overall trend.

Population justification
A global population of 1,200,000 breeding pairs, down from 1,430,000 pairs in the 1980s, is estimated based on figures from 1985-2011. This equates to an estimated global population of c.3 million mature individuals, based on the estimated number of breeding pairs extrapolated according to a ratio from Brooke (2004).

Trend justification
Globally, data on long-term trends are still lacking for most colonies. A decline is inferred from a drop in burrow occupancy of 28% over 20 years on Bird Island, South Georgia (Berrow et al. 2000a), and declines of 86% during 1981-1993 at sea in Prydz Bay, Antarctica (Woehler 1996). Population monitoring on Marion Island between 1996-1997 and 1999-2000 recorded an annual decrease of 14.5% in the population. Data from the Crozet archipelago indicate a decline of 37% in breeding pairs between 1983 and 2004, based on population models and field estimates from two surveys (Barbraud et al. in litt. 2008). At-sea surveys in the southern Indian Ocean suggest a 35% decline during 1981-2007 (Péron et al. 2010a), and data from fisheries and a population model suggest that the population on the Kerguelen Islands may be in decline (Barbraud et al. 2009). No population trend estimates are available from the Auckland, Campbell, Antipodes or Prince Edward Islands, representing approximately 17% of the global population.
Even when colonies on Auckland, Campbell, Antipodes, Prince Edward and Kerguelen are assumed to be stable, based on an ongoing decline of 1.6% per year on South Georgia (ACAP 2009) and declines in the smaller population on Crozet, the overall global population is projected to decline by 52% over three generations from 1980 (C. Small and W. Misiak in litt. 2013). Martin et al. (2009) estimate a greater rate of decline for South Georgia (-1.9% per annum). If the population on Kerguelen was suspected to be declining, the rate of overall population decline could be higher. An updated assessment of the population on South Georgia is needed in order to fully assess the overall trend (ACAP Secretariat in litt. 2013).

Distribution and population

This species breeds on South Georgia (Georgias del Sur), Prince Edward Islands (South Africa), Crozet Islands, Kerguelen Islands (French Southern Territories), Auckland, Campbell and Antipodes Islands (New Zealand), and in small numbers in the Falkland Islands (Islas Malvinas). Recently revised population estimates give a global population of approximately 3 million mature individuals. This is based on estimates of 773,150 breeding pairs on South Georgia in 2007 (ACAP 2012), 23,600 breeding pairs (9,800 to 36,800) on Crozet (Barbraud et al. in litt. 2008), 186,000-297,000 pairs on the Kerguelen Islands (Barbraud et al. 2009), 186,000 (137,000–241,000) breeding pairs on the Auckland Islands and c.22,000 (15,000–29,000) breeding pairs on Campbell (Rexer-Huber et al. 2015, 2016). Between 59,000 and 91,000 pairs breed on Antipodes Island (range of two estimates; Sommer et al. 2010, 2011). At least 55 pairs breed on the Falkland Islands, on Kidney Island, New Island, Top Island and Bottom Island (Reid et al. 2007, Poncet et al. 2012). A survey in 2009 estimated the number of occupied nests to be c. 24,000 (20,000-28,000) on Marion Island and 9,000-15,000 on Prince Edward Island (Ryan et al. 2012). On Bird Island (South Georgia), the population has apparently decreased by 28% over 20 years (Berrow et al. 2000a), while in Prydz Bay (Antarctica), the number of birds at sea decreased by 86% during 1981-1993 (Woehler 1996). The species forages as far north as equatorial waters and south to the pack-ice edge off Antarctica (Berrow et al. 2000, Catard et al. 2000, Phillips et al. 2006, Rexer-Huber et al. in litt. 2016), and is distributed widely in all southern oceans (Croxall et al. 1984).

Ecology

It is a burrow-nesting annual breeder, laying in mid-October to mid-November (ACAP 2009). Chicks usually fledge in late April (Barbraud et al. 2009). Outside the chick-rearing period, White-chinned Petrels breeding on South Georgia travel to the Patagonian shelf to feed. White-chinned Petrels breeding on the Falkland Island (Islas Malvinas) also largely winter in the Patagonian shelf, but some migrate to waters off southern Chile (Phillips et al. 2006, Rexer-Huber et al. in litt. 2016). Satellite tracking and ring recoveries from birds on Crozet Islands show that they spend the non-breeding season off the coasts of South Africa and Namibia (Barbraud in litt. 2008), while non-breeding birds from Marion Island winter mainly off South Africa (GLS; Rexer-Huber et al. in litt. 2016). Individuals from the Kerguelen Islands also winter off the coasts of South Africa and Namibia over the Benguela Current (Péron et al. 2010b). Non-breeding White-chinned Petrels from the Auckland Islands winter off the coast of Peru, Ecuador and northern Chile (Rexer-Huber et al. in litt. 2016), while those from the Antipodes winter off Peru and Chile (Sommer et al. 2010).
The species feeds on cephalopods, crustaceans and fish (Berrow and Croxall 1999, Catard et al. 2000, Delord et al. 2010) and processing waste from fisheries or discarded longline baits. Birds range widely when searching for food resources, travelling up to 8,000 km on feeding forays in the breeding season (Berrow et al. 2000b, Catard et al. 2000, Phillips et al. 2006, Delord et al. 2010). Individuals breeding at the Crozet and Kerguelen Islands display a bimodal foraging strategy, conducting either short trips to the surrounding shelf or long trips ranging from subtropical waters in the north to Antarctic waters in the south (Catard et al. 2000). Individuals breeding at the Kerguelen Islands target the seasonal ice zone where melting sea ice is gradually broken into floes and forage almost exclusively in open water (Péron et al. 2010b). 

Threats

The main threat faced by this species is high rate of incidental mortality in longline fisheries, although bycatch mitigation measures are returning a significant decrease in mortality. Barbraud et al. (2009) estimated that any additional source of mortality that approaches 31,000 individuals would result in a population decline at the Kerguelen Islands. Only 30% of this number are killed in local waters, and even fewer are now killed due to the implementation of mitigation measures. However, many birds are killed in the waters of Namibia and South Africa, which make up the majority of the Benguela Current Large Marine Ecosystem, where individuals from the Kerguelen Islands spend the winter. As such, this has the potential to cause declines in the Kerguelen Islands population. The Namibian hake longline fishery is historically thought to represent one of the largest legal sources of bycatch, with an estimated 20,567 birds killed in 2010, of which White-chinned Petrels represented 85% (BirdLife International 2017). However, the Namibian government has taken steps to introduce fishery regulations enforcing boats to take measures to mitigate bycatch. This uses bird-scaring lines (BirdLife International 2014, 2015), which have been shown to reduce White-chinned Petrel bycatch by over 90% (Paterson et al. 2017), and better line-weighting to reduce the time taken to sink the baited hooks out of range of seabirds (BirdLife International 2014, 2015). In the South African hake trawl fishery, prior to the use of bird-scaring lines, approximately 1,800 individuals were killed annually (Watkins et al. 2007), with the species attending 99% of trawls (Hill 2006). However, in 2006, bird-scaring lines became a requirement to gain a vessel permit, likely resulting in reduced bycatch. Discards from the South African deep‐water hake fishery make up more than half the diet of white‐chinned petrels (Jackson 1988, Crawford et al. 1991 per Watkins et al. 2007), likely increasing their vulnerability. It is estimated that the combined bycatch of South African pelagic and demersal fisheries amounts to 186 White-chinned Petrels annually (Petersen et al. 2007).

It is thought that fishery-related mortality exerts a greater pressure on the Indian Ocean population than the Atlantic Ocean population (Ryan et al. 2012). In the Indian Ocean, between 2001 and 2003 the legal longline fishery for Patagonian Toothfish Dissostichus eleginoides killed around 12,400 White-chinned Petrels per year (Delord et al. 2005). Following the introduction of mitigation measures, this figure dropped to approximately 2,500 birds in the 2005-2006 season (CCAMLR 2006), and to 740 birds in the 2008-2009 season (CCAMLR 2010). In addition to this, a further 31,000-111,000 and 50,000-89,000 seabirds were killed by illegal, unreported and unregulated fishing vessels in 1997 and 1998 respectively, around 60% of which were White-chinned Petrel (CCAMLR 1997, 1998). However, by 2006, this figure had fallen to 4,583 seabirds killed (CCAMLR 2006). The White-chinned Petrel is one of the species most commonly found attending longline vessels off south-east Brazil during winter (Olmos 1997, Bugoni et al. 2008) and off Uruguay (Jiménez et al. 2009). Artisanal fisheries off the South American coast have been demonstrated to cause significant bycatch mortality and very large numbers of small longlining vessels are the primary concern (Mangel 2012). It is the second most commonly-caught species in the Argentinean longline fleet, with an average capture rate for the period 1999-2003 of 0.014 ± 0.09 individuals per 1,000 hooks (Laich and Favero 2007). In the Australian Fishing Zone, more than 800 individuals are potentially killed annually (Gales et al. 1998) and in New Zealand between 2003 and 2005, 14.5% of all the seabirds caught in trawl and longline fisheries and returned for autopsy were P. aequinoctialis (Baird and Smith 2007).

Historically, human exploitation is thought to have caused extinction on the Chatham Islands (Carboneras et al. 2014). More recently, White-chinned Petrels have been targeted by an illegal artisanal fishery in Southern Angola for their meat and the use of their livers as bait (Petersen et al. 2007), however, this is not known to have caused a significant population decline.

Invasive and introduced species cause some threats across the White-chinned Petrel’s range. Introduced reindeer Rangifer tarandus also degraded breeding habitat on South Georgia (Poncet 2007), but have now been eradicated. However, some are still present on Grand Terre, Kerguelen, but overlap with a relatively small proportion of the population, upon which their impact is low. House Rats Rattus rattus are significant predators at some breeding sites, such as Crozet (Jones et al. 2008) and South Georgia (Clarke et al. 2012), and cats Felis catus predate nests at Kerguelen (Barbraud in litt. 2008), Cochons Island (Crozets) and Marion Island (Carboneras et al. 2014).

Conservation actions

Conservation and Research Actions Underway CMS Appendix II ACAP Annex 1. Population monitoring and foraging ecology studies are being undertaken at South Georgia, Crozet, Prince Edward and Kerguelen (Poncet 2007). Several breeding sites are in protected areas.

Conservation and Research Actions Proposed 
Continue and extend monitoring studies. Where feasible, eliminate alien predators and reindeer from breeding islands. Promote adoption of best-practice mitigation measures in all fisheries within the species range, including via intergovernmental mechanisms such as ACAP, FAO, and Regional Fisheries Management Organisations such as CCAMLR. Develop and implement plans to remove pigs from Auckland Island, rats, cats and reindeer from Kerguelen, and rats from Ile de la Possession, Crozet (Phillips et al. 2016).

Identification

55 cm. Large, black petrel with pale bill. Sooty-black with variable amount of white on throat and chin. Underside of primaries may appear silvery. Horn or yellow bill, with black between nostrils and bill tip. Similar spp. Largest all-dark shearwater or petrel. Bulkier than Westland Petrel P. westlandica and Black Petrel P. parkinsoni and lacks black bill tip. Spectacled Petrel P. conspicillata has diagnostic white eye-rings and dark tip to bill. Voice  Rattles at colony. Hints Powerful flight intersperses slow wingbeats and glides.

Acknowledgements

Text account compilers
Moreno, R., Small, C., Stuart, A., Taylor, J., Wheatley, H., Black, A., Anderson, O., Butchart, S., Calvert, R., Ashpole, J, Fjagesund, T., Hermes, C., Martin, R.

Contributors
Cooper, J., Hirst, P., Colabuono, F., Robertson, C., Bugoni, L., Phillips, R., Barbraud, C., Misiak, W., ACAP Secretariat, Ryan, P.G., Taylor, G.A., Martin, T., Small, C., Rexer-Huber, K., Makhado, A., Croxall, J.


Recommended citation
BirdLife International (2019) Species factsheet: Procellaria aequinoctialis. Downloaded from http://www.birdlife.org on 14/12/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 14/12/2019.