The Black-bellied Storm-Petrel is very closely related to the White-bellied Storm-Petrel (F. grallaria), as the name implies their belly color is different but they also differ in the average water temperature they choose. The Black-bellied prefers colder water and breeds to the south of the White-bellied, it is a true sub Antarctic breeder. Fregetta Storm-Petrels are generally grayish or blackish above, with a black hood, dark upperwings and tail with a pale carpal bar and white wing linings as well as largely white underparts below the hood. The Black-bellied does show a bold black central belly stripe, although in the field this can be difficult to see in profile with dark water as a background. The Black-bellied also has longer legs (which poke out behind the tail in flight), and darker upperparts than the White-bellied. Members of the Genus Fregetta forage in an unusual manner, skipping off waves using one leg, in an asymmetrical skip. The Black-bellied Storm-Petrel is found both in the Pacific and Atlantic Ocean basins but in South American waters it is associated with the Falklands and South Georgia, it is absent from the eastern Pacific. In winter it migrates north, although its winter distribution is not well known. It has occurred at least twice off the southeastern United States as a vagrant!