Northern giant petrel

Northern giant petrel
Flying over Godthul, South Georgia, British Overseas Territories
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Procellariiformes
Family: Procellariidae
Genus: Macronectes
Species: M. halli
Binomial name
Macronectes halli
Mathews, 1912[2]
Global range     Year-Round Range     Summer Range     Winter Range

The northern giant petrel (Macronectes halli), also known as the Hall's giant petrel, is a large predatory seabird of the southern oceans. Its distribution overlaps broadly with the similar southern giant petrel, though it overall is centred slightly further north.

Taxonomy

The northern giant petrel along with its counterpart, the southern giant petrel, make up the Macronectes genus. They come from the Procellariiformes order, which are referred to as tube-nosed seabirds, due to their unique nose structure. All tube-noses have tubular nostrils, and all Procellariidae have the openings on top of the upper portion of the bill. Procellariiformes also have between seven and nine distinct horny plates for their bill, and petrels have one of these plates that form the hooked portion of their upper bill called their maxillary unguis. They produce a stomach oil made up of wax esters and triglycerides that is stored in the proventriculus. This can be sprayed out of their mouths as a defence against predators as well as an energy rich food source for chicks and for the adults during their long flights.[3] Finally, they also 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 concentrated saline solution from their nostrils.[4]

Etymology

Macronectes giganteus can be broken down as makros a Greek word meaning "long" or "large" and nēktēs meaning "swimmer". Northern giant petrel starts with "northern" referring to their habitat being further north than their counterpart the southern giant petrel, and "petrel" refers to Saint Peter and from the story of him walking on water, which refers to how they run on top of the water as they are getting airborne.[5]

Description

On Salisbury Plain, South Georgia, British Overseas Territories
Swimming in Cooper Bay, South Georgia

The northern giant petrel averages 90 cm (35 in) in length, with a range of 80 to 95 cm (31 to 37 in), possessing a wingspan of 150 to 210 cm (59 to 83 in). Size is somewhat variable and this species is broadly the same size as its southern sister species. The largest-bodied colony is in the South Georgia Islands, where 56 males averaged 4.9 kg (11 lb) and 43 females average 3.72 kg (8.2 lb).[6] The smallest-bodied are on the Chatham Islands, where 19 males averaged 3.66 kg (8.1 lb) and 21 females averaged 2.83 kg (6.2 lb).[7] Overall, weight for the species can range from 2.5 to 5.8 kg (5.5 to 12.8 lb).[6][7] Its plumage consists of grey-brown body with lighter coloured forehead, sides of face, and chin. Its bill is between 90 and 110 mm (3.5–4.3 in) long, being slightly longer on average than the southern giant petrel, and is pinkish yellow with a brown tip, and its eyes are grey. The tarsus of the northern giant petrel is slightly longer on average than the southern species as well, but the southern has longer wings on average.[7] The juvenile of this species is completely dark brown and lightens as it ages. It can be differentiated from the similar coloured southern giant petrel by the top of the bill, which on the southern is green.[8]

Behavior

Feeding

The northern giant petrel feeds mainly on carrion from penguins and pinnipeds, as well as krill, offal, cephalopods, and discarded fish and waste from ships. During the breeding season, males eat more carrion than females with the females feeding on pelagic sources.[8]

Breeding

Birds start breeding at an average age of ten years, and breed on islands in colonies, which they share with the southern giant petrel. They breed six weeks earlier than their counterpart though.[8]

Range and habitat

They are pelagic and fly throughout the Southern Oceans north of the Antarctic Convergence Zone, and north through Chile, Argentina, South Africa, and half of Australia. They nest on islands with the South Georgia group with 4,500 pairs. They also nest on some of the Chatham Islands, Kerguelen Islands, Crozet Islands, Macquarie Island and others. Their overall occurrence range is 82,600,000 km2 (31,900,000 sq mi).[8]

Conservation

Breeding population and trends[8]
Location Population Date Trend
South Georgia 4,500 pairs 2005 Increasing 30% per 20 yr
Forty-Fours 2,000 pairs 2000
Middle Sister 80–100 pairs 2000
Kerguelen Islands 1,450–1,800 pairs 1989
Crozet Islands 1,300 pairs 1989 Decreasing
Macquarie Island 1,300 pairs Stable or increasing
Prince Edward Islands 650 pairs Increasing
Antipodes Island 230 pairs2003
Campbell Island 230 pairs 2000
Auckland Islands 50 pairs2000
Total 17,000–21,000 2001 Increasing 34% per 10 yr
Immature birds are more common at higher latitudes.

Overall, their population stands between 17,000 and 21,000 mature birds, based on a 2001 estimate. This number has been increasing over the last two decades, though it was forecasted to decrease. This increase has allowed the IUCN to downgrade them from near threatened to least concern. Recent surveys have shown that most locations are increasing in numbers except for the Crozet Islands. This is probably due to increases in fish waste, better control on longline fishing, and more carrion from fur seals.[8]

Currently, this bird is listed on CMS Appendix II and ACAP Annex 1. Future plans are to maintain the surveys and counting of individuals, researching movement and migrations, continuing the trend of lowering the bycatch deaths by current means and if needed newer measures through CCAMLR, CMS, and FAO.[8]

Footnotes

  1. ↑ BirdLife International (2012). "Macronectes halli". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
  2. ↑ BirdLife International (2009a)
  3. ↑ Double, M. C. (2003)
  4. ↑ Ehrlich, Paul R. (1988)
  5. ↑ Gotch, A. T. (1995)
  6. 1 2 CRC Handbook of Avian Body Masses, 2nd Edition by John B. Dunning Jr. (Editor). CRC Press (2008), ISBN 978-1-4200-6444-5.
  7. 1 2 3 Carlos, C. J., & Voisin, J. F. (2008). Identifying giant petrels, Macronectes giganteus and M. halli, in the field and in the hand. Publishing Editor, 1.
  8. 1 2 3 4 5 6 7 BirdLife International (2009)

References

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