The White-chinned Petrel or Cape Hen, Procellaria aequinoctialis, is a large shearwater in the family 
Procellariidae. It ranges around the Southern Oceans as far north as South Australia, Peru and Namibia, and breeds colonially on scattered islands.
The White-chinned Petrel is a member of the Procellaria genus, and in turn is a member of the Procellariidae family, and the Procellariiformes order. As a member of the Procellariiformes, they share certain identifying features. First, they have nasal passages that attach to the upper bill called naricorns. Although the nostrils on the Prion are on top of the upper bill. The bills of Procellariiformes are also unique in that they are split into between 7 and 9 horny plates. 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. 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 high saline solution from their nose.
Etymology
Procellaria comes from two Latin words, procella meaning a storm and arius a suffix meaning pertaining to. This is in reference to their association with stormy weather. The word Petrel is derived from St. Peter and the story of his walking on water. This is in reference to the Petrels habit of appearing to run on the water to take off.
Description
The White-chinned Petrel averages 55 cm (22 in) in length. This large petrel is sooty-black and has some white on its throat and chin. Its primaries can have a silvery appearance underneath. Its bill may be horn or yellow with a black tip, and also black between the nostrils. It has black feet.[2] When it flies, it mixes slow wing beats with glides. Although normally quiet, it will rattle or groan while at its colony.
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