Giant petrel
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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), the two species, the Southern Giant Petrel (M. giganteus) and Northern Giant Petrel (M. halli) are the largest members of the petrel family, Procellariidae, and considered, with the two fulmars to form a distinct sub-group within the petrels. Both species are restricted to the southern hemisphere, and though the ranges overlap greatly the Southern Giant Petrel nests further south, with colonies on Antarctica. Giant petrels are aggressive predators and scavengers, which has led to the other common name they were known as, the Stinker.
Giant petrels superficially resemble the albatross, and are the only procellarids with a comparable wingspan, around 190 cm. 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 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. Also, the underside of halli and the head and breast of dark-phase giganteus are lighter and more uniformly colored. Both differences are so slight that they are only useful at close distance and are, to untrained observers, even then only meaningful by direct comparison.
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, particularly that of seals and penguins. With that ability they are also the only petrel capable of walking well, they also display their dominance over carcasses with a "sealmaster posture": 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. At sea they feed on krill, squid and fish, often attending fishing fleets in the hope of picking up offal.
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 up off the ground (about 50cm high). 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 fleding.
References
- Brooke, M. (2004). Albatrosses And Petrels Across The World: Procellariidae. Oxford University Press, Oxford, UK ISBN 0-19-850125-0
- del Hoyo, Josep, Elliott, Andrew & Sargatal, Jordi (1992). Handbook of Birds of the World Vol 1. Barcelona:Lynx Edicions, ISBN 84-87334-10-5
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