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Genus Macronectes
Southern Giant-Petrel - The Southern Giant Petrel is one of two members of the genus Macronectes, which in turn, along with 14 other genera, comprise the Procellariidae family. Macronectes, also referred to as the Giant Petrels, along with the genus Fulmarus, Cape Petrel, Antarctic Petrel, and the Snow Petrel form a sub-family within the larger family.
Northern Giant-Petrel - 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 is used against predators as well as an energy rich food source for chicks and for the adults during their long flights.