Procellaria is a member of the
family Procellariidae and the
order Procellariiformes. As members of Procellariiformes, they share certain characteristics. First they have tubular nostrils called
naricorns. This feature gives them their common name, tubenoses. The opening to the nostril is located differently in some birds. These birds have the opening on top of the upper
bill. Second, they produce a
stomach oil that contains
wax esters and
triglycerides. This oil fills two functions. When predators threaten the birds or their chick or egg, they spit the substance on them. This substance has an awful smell, and mats the feathers down, degrading their usefulness. Also, they can digest the wax esters for a high energy source of food, during long flights or the period of time that they are
incubating their egg or caring for their young. They also have a uniquely structured bill, with seven to nine distinct horny plates. Finally, they have a
salt gland that is located above their nasal passages and helps desalinate their body, as they drink seawater. They excrete the salty waste out their nose. ==Distribution and habitat==