Main Foods Taken
Not well known; information anecdotal. In general, any small fish, squid, or crustacean that occurs near or at the surface is likely taken (e.g., less than about 5–6 cm long). The following prey have been observed: larval spiny lobster (Panulirus sp.; 71); larval fish and squid (66); lantern fish (72); fish, euphausiids, squid, caridean shrimp, gammarid amphipods (1); ephausiids (Thysanoessa spinifera in higher frequency; also Nyctiphanes simplex, Nematoscelis difficilis, Euphausia eximia, and E. recurva), larval fish (Vinciguerria lucetia), squid (Doryteuthis opalescens), amphipods, copepods, and decapods (Y. Bedolla-Guzmán, J. F. Masello, A. Aguirre-Muñoz, B. E. Lavaniegos, and P. Quillfeldt, unpublished data). Also scavenges larger items of food, presumably by tearing off pieces (e.g., 52, 73). At Islas San Benito, Black Storm-Petrel diet when feeding chicks contained consisted mainly of krill in colder years (2012 and 2013), while these were replaced by larval fish in a warmer year (2014) (Y. Bedolla-Guzmán, J. F. Masello, A. Aguirre-Muñoz, B. E. Lavaniegos, and P. Quillfeldt, unpublished data). Using stable-isotope analyses of whole blood and feathers, Black Storm-Petrels foraged in coastal waters (reflected in lower δ13C values), whereas Leach’s Storm-Petrel (Oceanodroma leucorhoa) and Least Storm-Petrel (O. microsoma) foraged further offshore both during breeding and nonbreeding periods (Y. Bedolla-Guzmán, J. F. Masello, A. Aguire-Muñoz, B. E. Lavaniegos, C. Voigt, J. Gómez-Gutiérrez, L. Sánchez-Velasco, and P. Quillfeldt, unpublished data).
Microhabitat for Foraging
Sea surface in areas of high productivity, such as shelf-break front off California (66, 57, 7), and thermal fronts bordering upwellings (65) and tide rips (68) in the Gulf of California. Sometimes forages in the company of small, slow cetaceans (e.g., bottlenose dolphin [Tursiops truncatus]), which likely drive suitable prey to the surface (61).
Food Capture and Consumption
Picks live organisms from sea surface by pattering, dipping, and contact-dipping (DGA). Most active foraging occurs during crepuscular periods, perhaps also at night. Dives to at least 1 m to obtain food, using its wings for propulsion, but not to pursue prey any distance (71, 8; B. Tershy, personal communication). Scavenges large floating items by swimming alongside and pecking at them. Attracted by olfaction to slicks of fish oil (52, 66, 61).