These are very big birds. 

Giant petrels are very big birds. 

Giant petrels are very large seabirds. They live in the Southern Hemisphere. There are two living kinds. One is the northern giant petrel. The other is the southern giant petrel. 


Giant petrels are huge seabirds from the Southern Hemisphere. They belong to a group called the genus Macronectes. This name comes from Greek words meaning "great swimmer." 

These birds have many ways to survive the ocean. They have a hooked bill called a maxillary unguis. This helps them hold onto slippery food like fish. They also make a special stomach oil. They store this oil in a part called the proventriculus. The birds can spray this oil from their mouths. They use it to defend themselves from enemies. They also use it to feed their hungry chicks. 
Scientists have studied these birds for a long time. An American expert named Charles Wallace Richmond named the genus in 1905. Before that, people used a different name. For a long time, people thought there was only one kind of giant petrel. They did not realize there were two separate species until 1966. One is the northern giant petrel, or M. halli. The other is the southern giant petrel, or M. giganteus. 
There are many specific facts about these two living birds. The southern giant petrel is slightly larger than the northern one. Its wingspan is 185 cm across. The northern giant petrel has a wingspan of 165 cm. 
Giant petrels are very different from the albatross. They look a bit like them, but their bills are different. Albatross nostrils are on the side of the bill. Giant petrel nostrils are joined on the top. 
Giant petrels are massive seabirds belonging to the genus *Macronectes*. This name comes from Ancient Greek words meaning "great swimmer." 
To survive in harsh marine environments, giant petrels have developed several specialized biological mechanisms. Their bills are split into seven to nine horny plates. They possess a hooked bill called a maxillary unguis. This structure helps them grip slippery prey like fish or squid. They also produce a specialized stomach oil made of wax esters and triglycerides. This oil is stored in a part of the stomach called the proventriculus. The birds can spray this oil from their mouths. They use it to defend themselves against predators. They also use it as a protein-rich food source for their chicks. Additionally, they have a salt gland located above the nasal passage. This gland helps them desalinate their bodies by excreting a high saline solution from their noses.
There are two living species of giant petrels that scientists study today. The first is the northern giant petrel, known as *M. halli*. The second is the southern giant petrel, known as *M. giganteus*. They were long considered the same species. However, they were established as separate species in 1966. 
Distinguishing between the two living species requires looking at specific physical details. The southern giant petrel is the larger of the two. It has a wingspan of 185 cm and a body length of 75 cm. The northern giant petrel is smaller, with a 165 cm wingspan and a 60 cm body length. Their plumage is mostly mottled grey. However, about 15% of southern petrels are almost completely white. You can also tell them apart by their bills. The billtip of *M. halli* is reddish-pink. The billtip of *M. giganteus* is pale green. Adults of the northern species typically have pale eyes. Adults of the southern species usually have dark eyes.
History shows how our understanding of these birds has evolved. The genus *Macronectes* was introduced in 1905 by the American ornithologist Charles Wallace Richmond. He created the name to accommodate the southern giant petrel. Before this, the name *Ossifraga* was used. However, that name was later found to belong to a different group of birds. The name "petrel" itself comes from the story of St. Peter walking on water. This refers to how the birds seem to run on the water surface when taking off.
Giant petrels are famous for their aggressive feeding behaviors. They are often called "stinkers" or "glutton birds" by sailors. On land, they scavenge carcasses in penguin and seal colonies. They use a "sealmaster posture" to show dominance over food. In this pose, they hold their head and wings outstretched. They even kill other seabirds, including large albatrosses, by battering or drowning them. 
Reproduction for these birds is a slow and careful process. Both species lay a single egg in a rough nest near the ground. The egg is incubated for about 60 days. Once the chick hatches, it is brooded for three weeks. The chicks fledge after about four months. However, they do not reach sexual maturity for six or seven years after fledging. 
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