A giant petrel, colloquially known as a stinker or glutton, is a large, predatory and scavenging seabird of the southern hemisphere. There are two species of giant petrel, the Northern Giant Petrel (Macronectes halli) and the Southern Giant Petrel (Macronectes giganteus), though they were considered a single species until 1966. The habitats of the two species overlap, and they are very similar in appearance.
The giant petrels are very large birds, weighing from 6.6 to 17.6 pounds (3 to 8 kg), similar in size to the albatross. The Southern Giant Petrel is a bit larger, while the Northern Giant Petrel is usually no larger than 11 pounds (5 kg). The giant petrels feature bills composed of seven to nine horny plates, with tube nostrils joined on the top of the bill and a hooked tip to grip slippery food. They also produce a stomach oil that can be used against predators, and have a saline gland above the nose to help secrete the excess saline they acquire from drinking sea water.
Giant petrels are the only member of their biological family able to walk on land efficiently. The two species look very similar, both with grey plumage and light orange beaks, though 15% of Southern Giant Petrels are white. The birds can be distinguished on the basis of their bill tip and eye color. The Northern species features a dark pink bill tip and pale eyes, while the Southern species has a light green bill tip and dark eyes.
Both giant petrel species are mainly predators at sea and scavengers on land, though they sometimes kill other seabirds for food by battering or drowning them. On land, they mainly feed on the carcasses of penguins and seals. While in they ocean, they prey on squid, krill, and fish. The birds sometimes follow fishing ships and eat discarded portions of the catch.
Giant petrels breed by laying a single egg in an above-ground nest. The egg is incubated for about two months. The young petrel can fly four months after birth, but only becomes sexually mature at six or seven years of age.
Both Northern and Southern Giant Petrels are of borderline conservation status, listed as endangered, threatened, or vulnerable by some agencies, but not by others. The Southern Giant Petrel may be more at risk. However, the populations of both species have increased in recent years.