Giant petrel

Giant petrels
Southern Giant Petrel juvenile
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Procellariiformes
Family:	Procellariidae
Genus:	Macronectes (Richmond, 1905)[1]
Species:	Macronectes giganteus Southern Giant Petrel Macronectes halli Northern Giant Petrel

Giant petrels is a genus from the family Procellariidae and consist of two species. They are the largest birds from this family. Both species are restricted to the Southern Hemisphere, and though their distributions overlap greatly with both species breeding on the Prince Edward Islands, Crozet Islands, Kerguelen Islands, Macquarie Island and South Georgia, many Southern Giant Petrel nest further south, with colonies as far south as Antarctica. Giant petrels are aggressive predators and scavengers, which has led to the other common name they were known as, the Stinker,^[2] and the whalers used to call them gluttons.

Taxonomy

The giant petrels are two large seabirds from the genus Macronectes. Long considered to be conspecific (they were not established as separate species until 1966),^[3] the two species, the Southern Giant Petrel, Macronectes giganteus, and Northern Giant Petrel, Macronectes halli, are considered with the two fulmars, Fulmarus, to form a distinct sub-group within Procellariidae, and if you add in the Antarctic Petrel, Cape Petrel, and the Snow Petrel, they form a separate group from the rest of the family.^[4]

Description

Giant petrels earn their name. The Southern Giant Petrel is slightly larger at 3–8 kg (6.6–17.6 lb), 180–210 cm (71–83 in) across the wings and 86–100 cm (34–39 in).^[2][5] The Northern Giant Petrel is 3–5 kg (6.6–11.0 lb), 150–210 cm (59–83 in) across the wings and 80–95 cm (31–37 in).^[6][7] They superficially resemble the albatross, and are the only procellarids who can equal them in size. They can be separated from the albatrosses by their bill; the two tube nostrils are joined together on the top of the bill, unlike on albatross where they are separated and on the side of the bill. They are also the only members of the Procellariidae family to have strong enough legs to walk effectively on land.^[2] They are also much darker and more mottled brown (except for the white morph Southern, which are whiter than any albatross) and have a more hunch-backed look. The bills of Procellariiformes are also unique in that they are split into between 7 and 9 horny plates. The Petrels have a hooked bill called the maxillary unguis which can hold slippery food. They produce a stomach oil made up of wax esters and triglycerides that is stored in the proventriculus. This is used against predators as well as an energy rich food source for chicks and for the adults during their long flights.^[8] Finally, they have a salt gland that is situated above the nasal passage and helps desalinate their bodies, due to the high amount of ocean water that they imbibe. It excretes a high saline solution from their nose.^[9]

They are harder to tell from each other, possessing similar long pale orange bills and uniform mottled grey plumage (except for 15% of Southern Petrels, which are almost completely white). The billtip of halli is reddish-pink and that of giganteus is pale green, appearing slightly darker and lighter than the rest of the bill, respectively. The underside of older halli is paler and more uniform than giganteus, the latter showing a contrast between paler head and neck and darker belly.^[10] Additionally, adult halli typically appear pale-eyed, while adult giganteus of the normal morph typically appear dark-eyed (occasionally flecked paler). Classic examples of Northern Giant are identifiable at some range. Unfortunately young birds of both species are all dark and very hard to distinguish unless bill tip colour can be seen. Some relatively young Northern Giant Petrels can appear to be paler on the head suggesting Southern Giant and thus this species is harder to confirm.

Etymology

Macronectes comes from the Greek words makros meaning long and nēktēs meaning swimmer. Also Petrel is derived from St. Peter and the story of his walking on water as they appear to run on the water when they take off.^[11]

Giant petrel feeding on a seal carcass in South Georgia.

Behavior

Feeding

Giant petrels are highly opportunistic feeders, uniquely for procellarids they will feed on land as well as at sea, in fact they find most of their food near the coast. On land they feed on carrion,^[2][10] particularly that of seals and penguins. They also display their dominance over carcasses with a "sealmaster posture":^[12] the head and the wings are held outstretched, the head pointing at the opponent and the wingtips pointing slightly back; the tail is raised to a vertical position. They are also capable of killing other seabirds, even those as large as an albatross, which they kill either by battering them to death (most commonly chicks of other species during the breeding season) or drowning.^[13] At sea they feed on krill, squid and fish, often attending fishing fleets in the hope of picking up offal.^[10]

Giant petrel with chick in Antarctica

Reproduction

The Southern Giant Petrel is more likely to form loose colonies than the Northern, both species laying a single egg in a rough nest built about 50 cm (20 in) off the ground. The egg is incubated for about 60 days, once hatched the chick is brooded for 3 weeks. Chicks fledge after about 4 months, but do not achieve sexual maturity for another 6–7 years after fledging.^[2]

Conservation

While both species are listed as Near Threatened in the 2008 Red List by the IUCN,^[14][15] recent evidence suggests they are less threatened than previously believed, and the populations of both actually appear to have increased, at least locally. Consequently they will be listed as Least Concern on the 2009 Red List.^[10][16]

The Southern Giant Petrel is listed as endangered on the Australian Environment Protection and Biodiversity Conservation Act 1999, while the Northern Giant Petrel is listed on the same Act as vulnerable.^[17] Their conservation status also varies from state to state within Australia. For example:

• Both the Southern and Northern Giant Petrels are listed as threatened on the Victorian Flora and Fauna Guarantee Act (1988).^[18] Under this Act, Action Statements for the recovery and future management of these species have been prepared.^[19]

• On the 2007 advisory list of threatened vertebrate fauna in Victoria, the Southern Giant Petrel is listed as vulnerable, while the Northern Giant Petrel is listed as near threatened.^[20]

Gallery

• 

  Giant petrel just killed a chick king penguin

• 

  Giant petrel flies above South Georgia Island

Footnotes

1. ^ Brands, S. (2008)
2. ^ ^{a b c d e} Maynard, B. J. (2003)
3. ^ Remsen Jr., J. V. (2008)
4. ^ Tree of Life (2008)
5. ^ http://www.heardisland.aq/nature/animals/fact_file_southern_giant_petrel.html
6. ^ http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=1061#description
7. ^ http://www.oiseaux.net/birds/northern.giant-petrel.html
8. ^ Double, M. C. (2003)
9. ^ Ehrlich, Paul R. (1988)
10. ^ ^{a b c d} BirdLife International (2009a)
11. ^ Gotch, A. F. (1995)
12. ^ de Bruyn, P. J. N. & Cooper, Æ J. (2005). "Who’s the boss? Giant petrel arrival times and interspecific interactions at a seal carcass at sub-Antarctic Marion Island" (Abstract). Polar Biology 28: 571–573. doi:10.1007/s00300-005-0724-7. http://www.springerlink.com/content/w6254pw62t21h411/. 
13. ^ Cox, J. B. (1978). "Albatross Killed by Giant-petrel". Emu 78 (2): 94–95. doi:10.1071/MU9780094. http://www.publish.csiro.au/?act=view_file&file_id=MU9780094.pdf. 
14. ^ BirdLife International (2008a)
15. ^ BirdLife International (2008b)
16. ^ BirdLife International (2009b)
17. ^ "EPBC Act List of Threatened Fauna". Australian government: Department of the Environment, Water, Heritage and the Arts. http://www.environment.gov.au/cgi-bin/sprat/public/publicthreatenedlist.pl?wanted=fauna. Retrieved 25 July 2009. 
18. ^ Department of Sustainability and Environment, Victoria
19. ^ Department of Sustainability and Environment, Victoria
20. ^ Victorian Department of Sustainability and Environment (2007)

References

• BirdLife International (2008a). Macronectes giganteus. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 16 Mar 2009.
• BirdLife International (2008b). Macronectes halli. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 16 Mar 2009.
• BirdLife International (2009a). "Southern Giant-petrel Macronectes giganteus - BirdLife Species Factsheet". Data Zone. http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=3870&m=0. Retrieved 16 Mar 2009. 
• BirdLife International (2009b). "Northern Giant-petrel Macronectes halli - BirdLife Species Factsheet". Data Zone. http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=3871&m=0. Retrieved 9 June 2009. 
• Brands, Sheila (14 Aug 2008). "Systema Naturae 2000 / Classification - Genus Macronectes -". Project: The Taxonomicon. http://www.taxonomy.nl/Main/Classification/51499.htm. Retrieved 16 Mar 2009. 
• Brooke, M. (2004). "Procellariidae". Albatrosses And Petrels Across The World. Oxford, UK: Oxford University Press. ISBN 0-19-850125-0. 
• Double, M. C. (2003). "Procellariiformes (Tubenosed Seabirds)". In Hutchins, Michael; Jackson, Jerome A.; Bock, Walter J. et al.. Grzimek's Animal Life Encyclopedia. 8 Birds I Tinamous and Ratites to Hoatzins. Joseph E. Trumpey, Chief Scientific Illustrator (2 ed.). Farmington Hills, MI: Gale Group. pp. 107–111. ISBN 0 7876 5784 0. 
• Ehrlich, Paul R.; Dobkin, David, S.; Wheye, Darryl (1988). The Birders Handbook (First ed.). New York, NY: Simon & Schuster. pp. 29–31. ISBN 0 671 65989 8. 
• Gotch, A. F. (1995) [1979]. "Albatrosses, Fulmars, Shearwaters, and Petrels". Latin Names Explained A Guide to the Scientific Classifications of Reptiles, Birds & Mammals. New York, NY: Facts on File. p. 191. ISBN 0 8160 3377 3. 
• del Hoyo, Josep, Elliott, Andrew & Sargatal, Jordi (1992). Handbook of Birds of the World Vol 1. Barcelona:Lynx Edicions, ISBN 84-87334-10-5
• Maynard, B. J. (2003). "Shearwaters, petrels, and fulmars (Procellariidae)". In Hutchins, Michael; Jackson, Jerome A.; Bock, Walter J. et al.. Grzimek's Animal Life Encyclopedia. 8 Birds I Tinamous and Ratites to Hoatzins. Joseph E. Trumpey, Chief Scientific Illustrator (2 ed.). Farmington Hills, MI: Gale Group. pp. 123–133. ISBN 0 7876 5784 0. 
• Remsen Jr., J. V.; et. al (07 Aug 2008). "A classification of the bird species of South America South American Classification Committee American Ornithologists' Union". South American Classification Committee. American Ornithologists' Union. http://www.aou.org/checklist/south. Retrieved 09 Jul 2009. 
• "Procellariidae. Shearwaters, Petrels". Tree of Life Web Project. 27 Jun 2008. http://tolweb.org/Procellariidae/26384. Retrieved 18 Mar 2009. 
• Victorian Department of Sustainability and Environment (2007). Advisory List of Threatened Vertebrate Fauna in Victoria - 2007. East Melbourne, Victoria: Department of Sustainability and Environment. p. 15. ISBN 978-1-74208-039-0.