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Black-vented Shearwater Puffinus opisthomelas

This species declined in the past owing to road building schemes and principally predation by introduced cats. However, these threats have ceased and the population may now begin to increase. Given the species's longevity it is retained as Near Threatened on the basis of the past declines.

Taxonomic source(s)
Brooke, M. de L. 2004. Albatrosses and Petrels Across the World. Oxford University Press, Oxford.
del Hoyo, J.; Collar, N. J.; Christie, D. A.; Elliott, A.; Fishpool, L. D. C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Barcelona, Spain and Cambridge UK: Lynx Edicions and BirdLife International.

34 cm. Medium-sized shearwater. Blackish-brown above and dirty white below. Transition at side of head from brown to white is poorly demarcated. Indistinct dusky collar may cross entire chest. Dusky brownish undertail-coverts and brownish thighs. White does not extend on to rump. Similar spp. Townsend's Shearwater P. auricularis is smaller with quicker wing-beats, clean cut black-and-white plumage and white flank patches. Pink-footed Shearwater P. creatopus is larger and flies higher. Audubon's Shearwater P. lherminieri is smaller.

Distribution and population
Puffinus opisthomelas breeds on six islands or small islets (including Guadalupe, San Benito and Natividad), off the Pacific coast of Mexico. Recent censuses have found the population to be much larger than previously thought. On Natividad, the population was estimated at 76,000 pairs in 1997 (Keitt 1998), compared with 5,000-10,000 pairs in 1991 (Everett and Anderson 1991). On San Benito, there are at least several thousand pairs (B. Tershy and B. Keitt in litt. 1999), but only 250-500 pairs were estimated in 1991 (Everett and Anderson 1991). On Guadalupe, the population was estimated at 2,500 pairs in 1991 (Everett and Anderson 1991). The current world population is estimated between 55,000 and 95,000 pairs, with the vast majority of the world's population (>95%) occurring on one island (Natividad) (B Keitt in litt. 2003). On Natividad, there was a 15% decrease in habitat and a 13-20% loss in burrows between c.1970 and the mid-1990s, and the estimated population decline was 4% per annum (Keitt 1998). Birds disperse mainly to the north reaching central California, USA, and rarely British Columbia, Canada (Carboneras 1992d).

Population justification
The total population is around 80,000 pairs, and therefore estimated here at 160,000 mature individuals, roughly equivalent to 200,000-250,000 total individuals.

Trend justification
The species declined dramatically owing to predation, in particular by introduced cats. However, eradication of these from its principal breeding island, Natividad, suggests that immediate threats to the species have now been significantly reduced and recruitment to the population may increase. Bycatch in fisheries remains a threat but its impacts are unknown.

Breeding takes place in burrows in sandy soil and rocky crevices. Birds attend colonies for at least 10 months of the year, arriving nocturnally to reduce predation by Western Gulls Larus occidentalis (Keitt et al. 2004). Eggs are laid in March and hatching begins in early May (Keitt 1998).

On Natividad, predation by c.20 feral cats reduced the population causing >1,000 recorded deaths per month prior to their eradication which reduced mortality to less than 100 per month (Keitt et al. undated). Road construction and the establishment of a small fishing community have decreased breeding habitat and burrows (Keitt 1998), and trampled burrows and lights continue to cause some mortality (Keitt unpublished data). The Guadalupe population is thought to be predated by cats and dogs (B. Tershy and B. Keitt in litt. 1999). It is possible that cat predation has caused the extirpation, or at the very least, significantly reduced populations of this species from the main island of Guadalupe (Keitt et al. 2006). In 2003, remains were found on cliffs at the southwest edge of Guadalupe in excellent potential nesting habitat. It is not known if these observations indicate breeding or prospecting birds. The presence of habitat inaccessible to cats provides hope that this species may still breed in small remnant populations on the main island of Guadalupe (Keitt et al. 2006). Calls from prospecting adults in the cliffs of Melpomene Arroyo, indicate birds are readily available to recolonize the main island in the absence of cat predation (Keitt et al. 2006). On all islands, introduced herbivores (donkeys, goats, sheep and rabbits) have caused erosion (reducing soil for burrows), trampled burrows and destroyed vegetation, and rabbits may have displaced birds from burrows (Keitt 1998, B. Tershy and B. Keitt in litt. 1999). Gill-net fisheries may cause some mortality (Carboneras 1992d). Successful eradication of cats on Natividad has been demonstrated to dramatically lower breeding season mortality (Keitt et al. 2002).

Conservation Actions Underway
Natividad is a core area of the Vizcaino Biosphere Reserve, where there is some active management. In 1997-1998, goats and sheep were removed with the cooperation of the local fishing community (Keitt 1998) Cats were controlled in 1998, and eradicated by 2002 (B. Tershy and B. Keitt in litt. 1999, Keitt et al. undated). In 1998-1999, introduced herbivores were eradicated from San Benito (B. Tershy and B. Keitt in litt. 1999). Guadalupe is designated as a biosphere reserve (S. N. G. Howell in litt. 1998), but there is little active management (B. Tershy and B. Keitt in litt. 1999). Conservation Actions Proposed
Monitor the population. Prohibit future road construction on Natividad and remove rubbish (B. Tershy and B. Keitt in litt. 1999). Close the middle and west San Benitos Islands to visitors (B. Tershy and B. Keitt in litt. 1999). Prevent future introductions of non-native predators and ensure all breeding islands remain cat-free (B. Tershy and B. Keitt in litt. 1999).

Brooke, M. De L. 2004. Albatrosses and petrels across the world. Oxford University Press, Oxford.

Carboneras, C. 1992. Procellariidae (Petrels and Shearwaters). In: del Hoyo, J.; Elliott, A.; Sargatal, J. (ed.), Handbook of the birds of the world, pp. 216-257. Lynx Edicions, Barcelona, Spain.

Everett, W. T.; Anderson, D. W. 1991. Status and conservation of the breeding seabirds on offshore Pacific islands of Baja California and the Gulf of California. In: Croxall, J.P. (ed.), Seabird status and conservation: a supplement, pp. 115-139. International Council for Bird Preservation, Cambridge, U.K.

Keitt, B. S. 1998. Ecology and conservation biology of the Black-vented Shearwater (Puffinus opisthomelas) on Natividad Island, Vizcaino Biosphere Reserve, Baja California Sur, México. Thesis. M.S., University of California, Santa Cruz.

Keitt, B. S.; Henry, R. W.; Aguirre, A.; Garcia, C.; Mendoza, L. L.; Hermosillo, M. A.; Tershy, B.; Croll, D. 2006. Impacts of introduced cats (Felis catus) on the Guadalupe island ecosystem. In: Prado, G. K. S., Peters, E. (ed.), Taller sobre la restauración y conservación de Isla Guadalupe: memorias., pp. 10. Instituto Nacional de Ecología, Mexico City.

Keitt, B. S.; Wilcox, C.; Tershy, B. R.; Croll, D. A.; Donlan, C. J. 2002. The effect of feral cats on the population viability of black-vented shearwaters (Puffinus opisthomelas) on Natividad Island, Mexico. Animal Conservation 5(3): 217-223.

Keitt, B.S.; Tershy, B. R.; Croll, D. A. 2004. Nocturnal behavior reduces predation pressure on Black-vented Shearwaters Puffinus opisthomelas. Marine Ornithology 32: 173-178.

Keitt, B.S.; Tershy, B. R.; Croll, D. A. Undated. Breeding biology and conservation of the Black-vented Shearwater.

Further web sources of information
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Text account compilers
Anderson, O., Benstead, P., Bird, J., Calvert, R., Capper, D., Isherwood, I.

Howell, S., Keitt, B.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2014) Species factsheet: Puffinus opisthomelas. Downloaded from on 31/07/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from on 31/07/2014.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

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To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Additional resources for this species

ARKive species - Black-vented shearwater (Puffinus opisthomelas) 0

Key facts
Current IUCN Red List category Near Threatened
Family Procellariidae (Petrels, Shearwaters)
Species name author Coues, 1864
Population size 160000 mature individuals
Population trend Unknown
Distribution size (breeding/resident) 2,170,000 km2
Country endemic? Yes
Links to further information
- Additional Information on this species