Effects of Human Activity
Pesticides and Other Contaminants/Toxics
Like other storm-petrels, likely vulnerable to oil spills (94) and pesticides (95). No direct data on this subject exist for this species (see Conservation and Management: Management).
Ingestion of Plastics, Lead, etc.
Storm-petrels readily ingest plastic particles floating on the sea, and for some species this can lead to, at the least, a decrease in body condition (96). No evidence has been found to indicate an issue for this species, though diet samples have been collected for analysis of microplastics (YBG).
Degradation of Breeding Habitat
Prehistorically, as with most seabirds, populations were likely limited by availability of predator-free islands (see Demography and Populations: Population Regulation); during historical times, the situation for the Black Storm-Petrel was exacerbated by introductions of domestic cats (Felis catus), rats (Rattus spp.), dogs (Canis lupus), rabbits (Oryctolagus cuniculus), and pigs (Sus scrofa), on nesting islands (e.g., Islas Coronado, Islas San Benito, Santa Barbara Island). These animals were introduced at unknown times by fishermen and seafarers, sometimes inadvertently and sometimes as a source of meat. As a consequence, seabird populations (including storm-petrels) likely have been reduced (44, 49). Within the species' breeding range on Pacific coast, feral cats have existed on 16 islands (now 2) where Black Storm-Petrel might well have nested, rats on 9 islands (now 8), and dogs on 2 islands (64, 84). Little is known about islands in the Gulf of California. Most substantial impact to burrowing seabirds occurred on islands < 3 km2 in area, in part (perhaps) explaining large Black Storm-Petrel population on Islas San Benito (where several introduced mammals have been exterminated; 83, 84). Terrain and presence of Cholla cactus likely protect storm-petrels on these islands, but cactus also poses a hazard to birds in flight.
Disturbance at Nest Sites
There is low disturbance on Isla San Benito Oeste by tourists who arrive on occasion to watch elephant seals (Mirounga angustirostris). They cross though a zone of storm-petrel burrows (Grupo de Ecología y Conservación de Islas, A.C., unpublished data).
Direct Human/Research Impacts
As in other storm-petrels (e.g., 87, 2) handling at nest site may cause desertion. The lights from fishermen's shacks and boats can cause a problem, but this issue has been controlled on Isla San Benito Oeste (YBG).
Species numbers in the low millions of pairs (see Demography and Populations: Population Status: Numbers). Thus, no special designation in terms of world population; may be considered vulnerable by some in United States owing to the very small populations in Channel Islands at northern periphery of species' range. In Mexico, listed as Threatened by NOM-059-SEMARNAT-2010 (Mexican Official Norm that lists the species or populations at risk; 97) .
Measures Proposed and Taken
Like all seabirds confined in nesting on offshore islands, the introduction of mammals, especially cats and rats, poses a continuous threat. Measures should be taken to guard against such introductions, for example prevention of invasive species by biosecurity programs, and to remove feral animals on islands where they have been introduced (e.g., 64, 84, 98).
Recently instituted measures may aid the Black Storm-Petrel (83, 84). Rats have been eradicated from 2 potential breeding islands (Rasa, Gulf of California; San Roque, Baja California Pacific coast), and eradication is under way at various other islands). Cats have been eradicated from 9 islands along Baja California Pacific coast (Coronado Norte, Coronado Sur, Todos Santos Norte, Todos Santos Sur, San Martín, San Jerónimo, Natividad, Asunción, San Roque); and have been eradicated from 7 potential breeding islands in the Gulf of California (Estanque, Mejía, Coronados, Monserrat, Santa Catalina, San Francisquito, Partida Sur). Rabbits (Orychtolagus cuniculus), donkeys (Equus africanus), goats (Capra aegagrus), and cactus mice (Peromyscus eremicus) have been eradicated from Islas San Benito; goats, dogs (Canis lupus) and sheep (Ovis aires) from Isla Natividad. The Flora and Fauna Protection Area Gulf of California Islands, several marine Natural Protected Areas along the Gulf of California, and the Baja California Pacific Islands Biosphere Reserve have been established by the government of Mexico, which is proceeding with measures and dissemination of information to the public that should aid conservation efforts.
Among the California Channel Islands, a recent problem may result from the immense increase in squid-fishing vessels near to shore during summer (99, 100). These boats, using very powerful lights (to attract squid), are spread densely over extensive areas near to island shore. In the lighted night sky, owl predation on small seabirds may be enhanced. No direct information on effect on Black Storm-Petrel.
Eggshell thinning and reduced hatching success owing to elevated levels of DDT and PCB evident in Ashy Storm-Petrel (O. homochroa) at Santa Cruz Island (101, 102). The same problem could have affected Black Storm-Petrel, which feeds even farther inshore (closer to pesticide source) than Ashy Storm-Petrel, at Islas Coronado and Channel Islands.
Effectiveness of Measures
Reduction in light pollution and of organochlorine pollution, along with social attraction, including artificial nest boxes, have restored the Ashy Storm-Petrel to parts of Santa Cruz Island (100), and could have positively affected the Black Storm-Petrel as well. Nest boxes also have proved effective for the Black Storm-Petrel (103).