Attractive petrel with a black mask, largely gray above and white below, with a diagnostic dark breast band. Note the heavy dark bill. In flight, exhibits gray underwings and gray and dark brown M-pattern on the back. The rare dark morph has dark underparts, but still retains the distinctive complete breast band, which is the most useful mark separating this species from Fea’s and Zino’s Petrels. Usually encountered well offshore, in towering roller-coaster flights; sometimes follows boats.