Justification of Red List Category
This species had shown a significant increase during the past two decades (probably owing to greater availability of carrion from expanding populations of fur seals, increased waste from commercial fishing operations, and the use of measures to reduce seabird bycatch around some breeding colonies). It no longer approaches the threshold for classification as threatened and is therefore classified as Least Concern.
The largest population is on South Georgia (Georgias del Sur), with c.4,310 pairs. followed by Chatham Islands (c.2000 pairs on the Forty-Fours and 80-100 pairs on Middle Sister), Iles Kerguelen (1,450-1,800 pairs), Iles Crozet (1,300 pairs), Macquarie Island (c.1,500 pairs), Prince Edward Island (464 pairs), Antipodes Island (233 pairs), Campbell Island (234 pairs) and the Auckland Group (100 pairs). In total, the population is estimated to number 11,800 breeding pairs.
Recent data indicate population increases may be occurring. In the 1980s, the world population was estimated to number c.8,600 pairs (Hunter 1985). A more recent estimate, is of 11,800 pairs (ACAP 2010), an apparent increase of >30 % (Patterson et al. 2008). A comprehensive survey of all known breeding sites in the South Georgia archipelago between 2005 and 2006 suggests that there has been a c.30 % increase in the last two decades (Poncet et al. in litt. 2008). The Marion Island and possibly the Prince Edward Island populations are also increasing. On Macquarie Island, the population showed a steady increase up until 2009, where the population peaked at an estimated 1,800-1,900 breeding pairs. A substantial mortality event associated with non-target/secondary poisoning during the Macquarie Island Pest Eradication Project aerial baiting phase in 2010 and 2011, reduced the population to pre-2000 levels (R. Alderman unpubl. data). Subsequent monitoring and modelling predict full recovery and continuation of increase for this population (Tuck et al. in prep.). The Possession Island (Crozet) population, which decreased between the 1980s and 1992, may now be increasing (Bretagnolle et al. 1991, H. Weimerskirch unpubl. data). These increases probably reflect greater availability of carrion from expanding populations of fur seals Arctocephalus gazella and A. tropicalis, increased waste from commercial fishing operations (Patterson et al. 2008), and use of measures to reduce seabird bycatch around some breeding colonies, such as South Georgia (Georgias del Sur). A 2003 census on the Antipodes Islands counted 230 breeding pairs (Wiltshire and Hamilton 2003), but trends are not known at present.
Macronectes halli breeds at South Georgia (Georgias del Sur), Prince Edward Islands (South Africa), Crozet and Kerguelen Islands (French Southern Territories), Macquarie Island (Australia), Auckland, Campbell, Antipodes and Chatham Islands and, historically, on islets off Stewart Island (New Zealand). The world population in the 1980s was estimated at c.8,600 pairs (Hunter 1985). A more recent estimate is 11,800 pairs (ACAP 2010). The population of Northern Giant Petrel has shown both decreases and dramatic increases across their breeding range (ACAP 2010). Increasing trends may be partly attributed to better monitoring, but also probably reflects greater availability of carrion from expanding populations of fur seals Arctocephalus gazella and A. tropicalis, increased waste from commercial fishing operations (Patterson et al. 2008), and use of measures to reduce seabird bycatch around some breeding colonies, such as South Georgia (Georgias del Sur).
Where they co-exist at the same location, Northern Giant Petrels breed approximately six weeks before Southern Giant Petrels (Hunter 1987, De Bruyn et al. 2007, Brown et al. 2015), though low levels of hybridisation occur on Macquarie Island and at South Georgia (Brown et al. 2015, and R. Alderman pers. comm.). Birds feed on penguin and pinniped carrion, cephalopods, krill, offal, discarded fish and refuse from ships, often feeding near trawlers and longliners (Hunter and Brooke 1982, Hunter 1983). Males and females exhibit clearly defined spatial segregation in foraging ranges (Hunter 1983, Gonzalez-Solis et al. 2000, Becker et al. 2002, Gonzalez-Solis and Croxall 2005, Thiers et al. 2014). During the breeding season, males exploit scavenging opportunities in and around seal and penguin colonies and are coastal in distribution, whereas females are much more dependent on pelagic resources (Quintana and Dell'Arciprete 2002, Patterson and Fraser 2003, BirdLife International 2004). There is significant sexual dimorphism, with female mass approximately 80% that of males (Gonzalez-Solis 2004). Ringing recoveries indicate juveniles forage more widely than adults (Hunter 1984a). At some sites, its less colonial breeding habit may make it less sensitive to human disturbance than Southern Giant Petrel, though their degree of coloniality does not differ on South Georgia (Georgias del Sur), the largest breeding colony (R. A. Phillips in litt. 2008). On the Chatham Islands, regurgitations from the birds on the Forty-Fours indicate a reliance on natural food sources (esp. Gnathophausia ingens) rather than carrion - there being no penguin colonies in the Chatham Islands (C. J. R. Robertson in litt. 2008). Average age of first breeding is c.10 years, and mean adult annual survival at South Georgia is 90% (Hunter 1984a).
A total of 2,000-4,000 giant petrels were estimated killed in illegal or unregulated Southern Ocean longline fisheries for Patagonian Toothfish, Dissostichus eleginoides, in 1997-1998 (CCAMLR 1997, 1998). Improved mitigation in a number of Patagonian Toothfish longline fisheries around breeding colonies (including South Georgia [Georgias del Sur]) has led to a reduction in observed bycatch of this species in these areas. Mortality associated with IUU fishing may still be a threat. On the Chatham Islands, fisheries bycatch returned by observers from NZ waters 1996-2005 returned only 17 birds (8 from trawl fisheries and 9 from longline) (C. J. R. Robertson in litt. 2008).
Conservation Actions Underway
CMS Appendix II and ACAP Annex 1.
90 cm. Giant petrel with huge bill. Adult: grey-brown body with paler forehead, sides of face and chin; bill 90-105 mm, pinkish-yellow horn tipped pink-brownish; eye grey to off-white; juvenile: completely dark brown fading with age. Similar spp. M. giganteus has whiter head, and is occasionally completely white; eye generally brown; pale leading edge to wing; tip of bill green.
Text account compilers
Symes, A., Wheatley, H., Hermes, C., Fjagesund, T., Martin, R., Black, A., Moreno, R., Bird, J., Stuart, A., Sullivan, B.
Phillips, R., Croxall, J., Weimerskirsch, H., Alderman, R., Robertson, C., Baker, B., Delord, K., Patterson-Fraser, D.
BirdLife International (2021) Species factsheet: Macronectes halli. Downloaded from http://www.birdlife.org on 24/10/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 24/10/2021.